Questions as text
Q1 · Explain how dredging affects water quality, productivity and food webs in marine… 9693/41 May/June 2017
3 (a) Explain how dredging affects water quality, productivity and food webs in marine environments. … … … … … … … … … … … … … … … … … … [7] (b) Explain the possible ecological consequences of using marine antifouling paints. … … … … … … … … … … [3] (c) Genetically engineered fish have recently been produced that contain a fluorescence gene from jellyfish. The fish fluoresce, glowing green, when under conditions of environmental stress such as the presence of pollution. (i) State the meaning of the following terms. genetic engineering … … selective breeding … … [2] (ii) Suggest benefits and risks of using these fish as indicators of pollution. … … … … … … … [3] [Total: 15]
15 marks
Mark scheme: 3(a) water quality- at least 1 of: (a) stirring up silt / substrate / sediment / sand / mud OR increases turbidity (b) idea of, reduces light penetration / AW ; (c) silt damaging gills ; (d) release of, toxins / heavy metals, from substrate ; (e) nutrient release can cause, algal blooms / eutrophication / description of ; productivity & food webs – max 6 of: (f) reduced photosynthesis ; (g) less primary productivity ; (h) loss of, food / energy, for primary consumers / herbivores ; (i) damaging, habitats / seabed / substrate / coral / reef ; (j) (toxins / heavy metals / chemicals) bioaccumulate / description of ; (k) difficult for predators to see prey ORA / affects on breeding ; (l) increased food for / benefits, (some) filter feeders / shellfish ; 7 I seabed unqualified A idea of, silt / AW damages coral polyp A named toxins – not antifouling paint ; I reduced oxygen unqualified A nutrient release from sediment causes increase in productivity Productivity needs to be in context of producers or plants or less photosynthesis. I productivity unqualified e.g. can’t find mates, damage to gametes / larvae Question Answer Marks Guidance 3(b) any 3 of: (Antifouling paint contains) TBT / mercury / copper / lead / heavy metals bioaccumulation / biomagnification / not broken down / pass along food chains / AW ; ref. to, sex reversal of molluscs / imposex in molluscs / sterility in molluscs / interferes with sex ratio in molluscs ; idea of, (resulting in) less food for later trophic level ; 3 A marine named examples of molluscs 3(c)(i) (Genetic engineering) changing of the, genetic material / DNA / genes / alleles, of an organism ; (Selective breeding) (humans choose) individuals (of same species) mated for specific characteristics / alleles / traits ; 2 Individuals are selected for a particular feature to breed 3(c)(ii) benefits-at least 1 of: cheap method (for detecting pollution) ; quick / in-situ method ; can be used by unskilled operator / little training needed ; risks-at least 1 of: escape / get into the wild ; breed with native species / transfer gene into wild populations ; any other qualified risk escape / getting into the wild, e.g. food chain effect / competition ; 3
This question in 9693/41 May/June 2017
Q2 · Many areas of coastline in tropical countries are experiencing increased tourism 9693/41 May/June 2017
4 (a) Many areas of coastline in tropical countries are experiencing increased tourism. Discuss the conflicts of interest that could arise between the stakeholders of an existing fishing industry and a developing tourist industry on a region of tropical island coastline. … … … … … … … … … … … … … … … … … [6] (b) (i) Aquaculture is being increasingly used as a method of conserving commercial fish stocks. Describe and explain the requirements of a successful, sustainable aquaculture venture. … … … … … … … … … … … … [5] (ii) Discuss the advantages and disadvantages of the introduction of cultivated fish into wild populations. … … … … … … … … … … … … [4]
15 marks
Mark scheme: 4(a) negative conflict of tourism on fishing- at least 1 of: (a) loss / damage to fishing areas / reefs / habitats / beaches ; (b) loss of nursery / spawning grounds ; (c) reduced fish population / reduced catch ; (d) damage to nets / fishing gear ; (e) loss of fishing areas, due to bans / protected zones / conservation zones ; (f) idea of, (more) pollution / litter / sewage ; (g) tourist industry takes employment / not enough people to enter fishing / conflict of employment ; (h) idea of, tourism raises cost of living for fishermen / prices rise / inflation / loss of housing / AW ; (i) reduced income (from fishing) ; (j) loss of harbour space ; (k) fishing boats conflict with tourist boats for space ; 6 To award full marks, at least one mark should be from each section I environment I noise pollution and light pollution award income mark once only award boat conflict mark once only Question Answer Marks Guidance negative conflict of fishing on tourism – at least 1 of: (l) idea of, fisheries are unsightly ; (m) fishing boats conflict with tourist boats for space ; (n) fishing (boats) may endanger tourists ; (1) fishing may deplete fish / coral / habitat, that attract tourists ; (2) reduced income (from tourism) ; A unpleasant smell award boat conflict mark once only award income mark once only Question Answer Marks Guidance 4(b) (i) any 5 of: (a) availability of stock / adults for spawning / brood stock ; (b) (so that) fish are not taken from wild / not depleting wild stocks ; (c) availability of food (stocks) ; (d) that is not from wild / e.g. uses fish waste / trimmings / AW ; (e) water purification systems / clean water / low stocking density / don’t over feed ; (f) to reduce, pollution / disease spread / for disease management / prevent eutrophication ; (g) minimise use of, antibiotics / pesticides ; (h) to prevent development of resistance ; (i) available labour force / AW ; (j) availability of location OR suitable location that does not destroy habitats / mangroves ; (k) transport access / roads / rail, for supplies in and / or products out ; (l) sufficient profit potential / idea of, economic benefit / AW ; (m) (due to) market demand / access to export market / suitable exchange rates ; 5 Question Answer Marks Guidance 4(b) (ii) advantage- at least 1 of: (a) rehabilitation of depleted stocks / replenishing populations / AW ; (b) restoring food webs / ecological balance ; disadvantage- at least 1 of: (c) (however) genetically weak stocks / weakens gene pool / inbred fish / poor genetic diversity / deleterious alleles transfer to wild ; (d) cultivated stocks are not well adapted / are weaker / susceptible to predators / AW ; (e) spread disease / parasite transfer ; (f) over-population / over-predation / damage to food chains / idea of, competition ; 4 To award full marks, at least one mark should be from each section (i.e. at least one advantage and one disadvantage) A named examples of diseases / parasites
This question in 9693/41 May/June 2017
Q3 · Mass tourism in coastal areas can have negative effects on marine environments 9693/40 May/June 2018
4 (a) Mass tourism in coastal areas can have negative effects on marine environments. These can be caused by large scale agriculture to meet the demands for food and the use of desalination plants to meet the demands for fresh water. (i) Explain the negative ecological impacts of agriculture on the marine environment. … … … … … … … … … [4] (ii) Explain the negative ecological impacts of desalination plants on the marine environment. … … … … … … … … … [4] (b) Damage to the marine environment can be reduced by responsible tourism practices. A new coastal ecotourist resort is planned. Describe the responsible practices that should be included in the development of this resort. … … … … … … … … … … … … … … … [7] [Total: 15]
15 marks
This question in 9693/40 May/June 2018
Q4 · In 2010, the Deepwater Horizon oil platform exploded causing a large oil spill in the… 9693/40 Oct/Nov 2018
3 In 2010, the Deepwater Horizon oil platform exploded causing a large oil spill in the Gulf of Mexico. The effects of the spillage have been felt for many years since. (a) Explain how oil on the surface of the water would have affected food webs in the open ocean. … … … … … … … … … … … … … … … [6] (b) The oil killed seagrass and large areas of mangrove around coastal areas. Explain how the death of seagrass and mangroves could affect marine ecosystems, other than the effects on food webs. … … … … … … … … … … … … … … … [6] (c) Describe how biotechnology could be used to help clean up oil spills. … … … … … … … [3] [Total: 15]
15 marks
This question in 9693/40 Oct/Nov 2018
Q5 · One method used to measure water pollution by organic waste is to calculate the… 9693/41 May/June 2019
2 One method used to measure water pollution by organic waste is to calculate the biological oxygen demand, BOD. This determines the rate at which oxygen is used by micro-organisms in the water. To determine the BOD of water, a sample of water is taken from the sea or river and the concentration of oxygen is measured. The sample is then placed in a tube with an airtight seal and kept at 20 °C for five days. The concentration of oxygen is then measured again. The fall in oxygen concentration is the BOD. (a) (i) Suggest why the airtight seals are placed on the tubes. … … [1] (ii) Explain why oxygen concentration falls in the tubes. … … … … [2] (b) The BOD of an estuary close to an agricultural area in Southeast Asia was measured during each month. Fertiliser use and rain levels were also monitored. The results are shown in Table 2.1. Table 2.1 month fertiliser use rain / mm BOD / mg dm–3 January low 15 2 February low 20 2 March low 25 3 April high 50 2 May high 310 8 June high 550 18 July high 575 25 August high 590 25 September low 360 19 October low 210 12 November low 75 8 December low 20 2 (i) Calculate the percentage increase in BOD between January and August. Show your working. … % [2] (ii) Explain the changes in BOD over the year. … … … … … … … … … [4] [Total: 9]
9 marks
Mark scheme: 2(a)(i) prevent, entry / loss, of oxygen ; 1 2(a)(ii) (microorganisms) respire / respiration ; using (organic) waste (in water) ; 2 R anaerobic respiration A using glucose / sugar / amino acids I food unqualified 2(b)(i) 1150 ; ; 2 2(b)(ii) any 4 of: (a) BOD is highest when fertiliser use is high and rain is high / ORA ; (b) fertiliser, dissolves in rain / runs off / leaches ; (c) increases growth of, algae / plants (in the water) OR eutrophication OR algal blooms ; (d) less photosynthesis (under algae / floating plants) ; (e) increased amounts of, dead material / decay / decomposition ; (f) (high) bacterial / decomposer / microorganism, respiration (rate) ; 4 A (primary) producer for plant A increased primary productivity
This question in 9693/41 May/June 2019
Q6 · Explain the meaning of the terms osmoconformer and euryhaline 9693/41 May/June 2019
3 (a) Explain the meaning of the terms osmoconformer and euryhaline. osmoconformer … … euryhaline … … [2] (b) Many marine organisms regulate their water and ion content. Outline the process of osmoregulation in marine bony fish and explain why this is necessary. … … … … … … … … … … … … … … … [7] (c) Discuss the possible ecological impacts of desalination plants on marine ecology. … … … … … … … … … … … … … [6] [Total: 15]
15 marks
Mark scheme: 3(a) osmoconformer: organisms that have salinity that is same as surrounding water / AW ; euryhaline: organisms that can tolerate a wide range of salinities / live in fresh and salt water / AW ; 2 potential 3(b) any 7 of: how (a) drinking ; (b) remove / excrete , salt / sodium / suitable named ion ; (c) by, gills OR kidney ; (d) active transport / uses energy or ATP / requires respiration ; (e) absorption of water by kidney ; (f) low amount of urine / hypertonic urine / concentrated urine ; why (g) salt water has a higher salinity than body fluids / AW ; (h) water will leave body / dehydration ; (i) due to osmosis ; (j) damaging, cells / tissues / AW OR not enough fluid to transport / AW ; 7 I freshwater I diffuse or any idea of passive process A active pumping / actively pumps sensible impact of the dehydration Question Answer Marks Guidance 3(c) any 6 of: (a) loss of biodiversity / disruption to, food chains / webs ; (b) idea of: benthic / sessile species affected in particular ; (c) releasing (large amounts of) brine / high salt concentration water ; (d) organisms lose water (by osmosis) ; (e) high temperature water is released ; (f) denaturing enzymes ; (g) altering rates of, chemical reactions / photosynthesis / respiration ; (h) lowered oxygen concentration ; (i) stirring up of sediment / increasing turbidity ; (j) (that) reduces photosynthesis / damages coral / damages gills / AW ; (k) release of, toxins / detergents / heavy metals / surfactants / acids / alkalis ; (l) (chemicals may) bioaccumulate / biomagnify / AW OR damage to gills OR other specific appropriate damage to organism ; (m) (killing of), organisms / eggs / larvae / plankton, due to entry (into desalination plant) ; 6 I reducing light intensity I TBT
This question in 9693/41 May/June 2019
Q7 · Describe how oxygen concentrations in water differ from those in air 9693/40 Oct/Nov 2019
3 (a) Describe how oxygen concentrations in water differ from those in air. … … … … [2] (b) There are many different methods of gaseous exchange used by marine organisms. Compare the methods of gaseous exchange in coral polyps and grouper. … … … … … … … … … … … … … … … … [8] (c) Explain the negative ecological impacts of the disposal of untreated sewage into the marine environment. … … … … … … … … … … [5] [Total: 15]
15 marks
This question in 9693/40 Oct/Nov 2019
Q8 · Gold mining causes the release of heavy metals, such as mercury, into estuaries 9693/40 Oct/Nov 2020
1 Gold mining causes the release of heavy metals, such as mercury, into estuaries. These heavy metals sink to the bed of the estuary. Some scientists have suggested that dredging of estuaries in areas where gold mining has occurred causes the release of mercury into the water. In January 2009, dredging was banned in an estuary in North America to reduce the release of mercury. A mining company objected to the ban on dredging and investigated the effect of the ban on the release of mercury into the water. They randomly sampled the concentrations of mercury in four species of organisms in the estuary, before and after dredging was stopped. The results are shown in Table 1.1. Table 1.1 species mean concentration of mercury in organism / parts per million 2007 2008 2012 A 42 30 61 B 60 41 50 C 65 50 81 D 190 101 120 (a) (i) State why the organisms were sampled randomly. … … [1] (ii) Plot a line graph to show the changes in concentration of mercury over time for each of the species in Table 1.1. Join your points with ruled, straight lines. Use a separate line for each species. [5] (iii) Species A consumes plants. Species D is a predator. Use this information to explain the differences between the concentrations of mercury in species A and species D in 2007. … … … … [2] (b) The mining company stated that dredging prevents mercury accumulating in the water and that sudden flooding of the estuary causes the release of mercury from the bed of the estuary. They provided data to show the concentration of mercury in the estuary in 2008 and 2009. The results are shown in Fig. 1.1. 300 250 flood flood 200 mercury concentration 150 in water / a.u. dredging 100 50 0 2008 2008 2008 2008 2008 2008 2009 2009 2009 2009 2009 2009 Jan Mar May Jul Sep Nov Jan Mar May Jul Sep Nov month Fig. 1.1 Use the information in Table 1.1 and Fig. 1.1 to discuss the claims of the mining company that banning dredging has led to increased release of mercury from the bed of the estuary. … … … … … … … … [4] [Total: 12]
12 marks
This question in 9693/40 Oct/Nov 2020
Q9 · Sand that has been contaminated with crude oil can be cleaned by specialised bacteria 9693/40 May/June 2021
2 Sand that has been contaminated with crude oil can be cleaned by specialised bacteria. These bacteria digest the oil. Algae are naturally present in the sand. Scientists investigated if adding fertiliser to the sand speeds up this digestion process. The investigation is described in the steps below. • Four 5 kg samples of sand were each mixed with 50 g of crude oil. • An equal mass of bacteria which digest oil was added to each sample of sand. • A different mass of fertiliser was added to each sample. • The samples were left for seven weeks. • The percentage reduction of crude oil in each sample was measured. • The mean dry mass of algae that grew in the sand was also measured. • The experiment was repeated five times. • The mean percentage reduction of crude oil, and the mean dry mass of algae, for each mass of fertiliser were calculated. The results are shown in Fig. 2.1. Key ± 1 standard deviation mean percentage reduction of crude oil mean dry mass of algae / g 60 2400 2200 50 2000 1800 40 1600 1400 mean percentage reduction of crude 30 1200 oil mean dry mass 1000 of algae / g 20 800 600 10 400 200 0 0 0 30 60 90 mass of fertiliser / g Fig. 2.1 (a) (i) Use Fig. 2.1 to calculate the percentage increase in mean dry mass of algae when the mass of fertiliser was increased from 0 g to 90 g. Space for working. … % [2] (ii) Describe the effect of increasing the mass of fertiliser on the mean percentage reduction of crude oil. … … … … [2] (b) The scientists concluded that 30 g of fertiliser per 5 kg sand is the ideal quantity to use to digest oil on sandy shores. Use Fig. 2.1 to explain why 30 g of fertiliser was chosen. … … … … … … … … … [4] [Total: 8]
8 marks
This question in 9693/40 May/June 2021
Q10 · Pollution by plastics and microplastics is affecting many marine ecosystems 9693/41 May/June 2022
1 Pollution by plastics and microplastics is affecting many marine ecosystems. (a) (i) State what is meant by the term microplastic. … … [1] (ii) Explain why microplastics in oceans and seas can pose a risk to humans. … … … … … … … … [4] (b) Scientists estimated the mass of plastic and microplastic in six different areas of oceans and seas shown in Fig. 1.1. North North Atlantic Mediterranean Pacific Ocean Sea Ocean South South Indian Pacific Atlantic Ocean Ocean Ocean Fig. 1.1 They collected plastic and microplastics from 20 locations within each of the areas over a period of six months. The results are shown in Fig. 1.2. 9.0 8.0 7.0 plastic 6.0 microplastic estimated mass 5.0 of plastic and microplastic / kg km–2 4.0 3.0 2.0 1.0 0.0 North Indian North Mediterranean South South Pacific Ocean Atlantic Sea Pacific Atlantic Ocean Ocean Ocean Ocean area of water Fig. 1.2 (i) The Mediterranean Sea has an estimated surface area of 2 500 000 km2. Use Fig. 1.2 to calculate the total estimated mass of microplastic in the Mediterranean Sea. State the correct unit. … [2] (ii) Suggest a reason for the relatively high estimated total mass of plastic found in the Mediterranean Sea. … … … … [2] (c) The scientists calculated the ratios of plastic : microplastic for each of the areas. The results are shown in Table 1.1. Table 1.1 area ratio of plastic : microplastic North Pacific Ocean 8.0 : 1.0 Indian Ocean North Atlantic Ocean 9.1 : 1.0 Mediterranean Sea 4.4 : 1.0 South Pacific Ocean 7.7 : 1.0 South Atlantic Ocean 11.0 : 1.0 (i) The estimated mass of plastic found in the Indian Ocean is 0.75 kg km–2. The estimated mass of microplastic found in the Indian Ocean is 0.09 kg km–2. Calculate the ratio of plastic to microplastic in the Indian Ocean. Give your answer to two significant figures. Write your answer in Table 1.1. [2] (ii) Suggest an explanation for the relatively low ratio of plastic to microplastic in the Mediterranean Sea. … … … … … … [3] [Total: 14]
14 marks
Mark scheme: 1(a)(i) plastic that is less than 5 mm (in diameter) ; 1 1(a)(ii) any 4 from: 1 microplastics bind to (organic), toxins / poisons ; 2 (microplastics) are consumed / taken up, by (marine) organisms ; 3 (microplastics / toxins) pass along food chains / AW ; 4 (microplastics / toxins) do not break down / (bio)accumulate ; 5 biomagnification occurs ; 6 humans consume high trophic level organisms / AW ; 4 1(b)(i) 4 750 000 ; kg ; 2 1(b)(ii) any 2 from: 1 higher population density around area / AW ; 2 less powerful currents to move plastic / AW ; 3 idea that Mediterranean is an enclosed water body ; 4 many large rivers (empty plastic into Sea) ; 5 there are countries with less waste disposal of plastic / fewer environmental, policies / laws / AW ; 2 1(c)(i) 8.3 : 1.0 ;; 2 1(c)(ii) any 3 from: 1 (more) plastic is degraded / broken down (into microplastics) / AW ; 2 (higher exposure to) UV light ; 3 (higher action of) wind ; 4 (higher action of) waves / turbulence; 5 warm(er) temperature ; 6 more direct release of (primary) microplastics ; 3
This question in 9693/41 May/June 2022
Q11 · High protein feed is often used in aquaculture 9693/41 May/June 2022
5 High protein feed is often used in aquaculture. It can cause the release of large quantities of urea into water. Urea is a nitrogen-containing compound that is excreted by many organisms and is also released from the breakdown of protein by decomposers. When urea enters marine waters, it can affect the growth of dinoflagellates and other algae. (a) Fig. 5.1 shows a light micrograph of a dinoflagellate. Fig. 5.1 Make a large drawing of the dinoflagellate in Fig. 5.1. Do not label or shade your diagram. [3] (b) To investigate the effect of urea from high protein feed, scientists analysed the water in a sea bass farm 21 times over a period of six months. Each time the water was analysed, the urea concentration and presence or absence of an algal bloom was assessed. The concentration of urea was assessed as either less than or equal to 1.5 μmol dm–3 or greater than 1.5 μmol dm–3. The results are shown in Table 5.1. Table 5.1 urea concentration number of times water contained number of times algal / μmol dm–3 urea of this concentration bloom occurred less than or equal to 1.5 7 1 greater than 1.5 14 10 (i) Calculate as a percentage the number of times that water with a urea concentration of greater than 1.5 μmol dm–3 also had an algal bloom. … % [1] (ii) Describe the relationship between the different concentrations of urea and the occurrence of the algal blooms. … … [1] (iii) Scientists claimed that the results showed that adding excess protein feed caused algal blooms. Evaluate this conclusion. … … … … … … [3] (c) Give two requirements for the long-term sustainability of an aquaculture venture. 1 … … 2 … … [2] [Total: 10]
10 marks
Mark scheme: 5(a) 1 clear, complete outline of structure with four ‘spikes’ and the flagellum and at least same size as photo ; 2 lines thin, continuous and no shading ; 3 correct proportions and angles of body, spikes and flagellum ; 3 5(b)(i) 71(.4…) (%) ; 1 5(b)(ii) any 1 from: 1 algal blooms are most likely to happen when the concentration is greater than 1.5 (mmol dm–3) / AW ; 2 correlation between urea concentration and chance of an algal bloom ; 3 as urea concentration increases there are more (algal) blooms / AW ; 1 5(b)(iii) 1 high protein / feed, causes high urea concentrations / releases urea / causes organisms to release urea / AW ; 2 there are more blooms when urea (concentration) is higher / more / ORA ; max 2 from: 3 it is a correlation not causation ; 4 other factors may cause the blooms ; 5 urea may not be from the protein feed / or from other sources ; 3 Question Answer Marks 5(c) any 2 from: 1 (availability of) stock ; 2 (availability of) clean water ; 3 (availability of) feed ; 4 efficiency of use of feed : 5 (availability of) labour / people to work there / people to run it ; 6 disease management / AW ; 7 cleaning / filtering of waste water (so environment is not polluted) ; 8 (availability of) location ; 9 market demand / AW ; 10 access to market / ability to transport to markets ; 11 return on investment / profitability ; 2
This question in 9693/41 May/June 2022
Q12 · Ammonium nitrate is commonly used as an agricultural fertiliser 9693/41 May/June 2022
6 Ammonium nitrate is commonly used as an agricultural fertiliser. If ammonium nitrate runs off into the sea, it can increase the rate of growth of marine algae. Plan a laboratory-based investigation that you could do to investigate the effect of changing the concentration of ammonium nitrate on the rate of growth of marine algae. You are provided with standard laboratory equipment. Your plan should: • include a clear statement of the hypothesis • identify the key variables • include full details of the method • describe how you would analyse your results • be safe and ethical. … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … [12]
12 marks
Mark scheme: 6 one mark for hypothesis hypothesis (h): 1 increase in ammonium nitrate increases rate of growth of algae / AW ; any 11 from other sections: safety and ethical treatment (e) 2 wear, safety glasses / gloves, with reason ; 3 remove any animals / fish from tanks / do not release chemicals into open water / do not wash chemicals / algae down drain / do not release algae into open water / AW ; independent variable (i) 4 independent variable: concentration of ammonium nitrate ; 5 at least 5 stated concentrations ; 6 control experiment with no ammonium nitrate ; dependent variable (d) 7 dependent variable: rate of growth / mass of algae ; 8 measure, (dry) mass of algae / weigh algae / light penetration / height of algae in tank / surface area of algae / counting cell number / AW ; 9 leave algae for stated time (more than one day) ; controls (c) max 3 controls from: 10 same, (starting) mass / species / type / age, of algae ; 11 light (intensity) ; 12 provide other minerals / keep other minerals constant ; 13 temperature ; 14 pH / salinity ; 15 volume of water / solution / volume of tanks ; 16 carbon dioxide ; Question Answer Marks 6 method and techniques (m) max 3 from: 17 (use of) pipettes / syringe / measuring cylinder (to measure volumes) ; 18 (use of) water-bath to maintain temperature / AW ; 19 (use of) balance to weigh algae ; 20 (use of) oven to dry algae ; 21 (use of) sodium hydrogen carbonate as source of carbon dioxide ; analysis (a) max 2 from: 22 replicates / several repeats and calculate mean / identify anomalies / outliers / identify if errors had occurred ; 23 calculation of rate as (change of) mass over time / AW ; 24 correct statistical test ; 25 plot graph of rate of growth / mass, against concentration of ammonium nitrate / AW ; dependent variable (d) 7 dependent variable: rate of growth / mass of algae ; 8 measure, (dry) mass of algae / weigh algae / light penetration / height of algae in tank / surface area of algae / counting cell number / AW ; 9 leave algae for stated time (more than one day) ; controls (c) max 3 controls from: 10 same, (starting) mass / species / type / age, of algae ; 11 light (intensity) ; 12 provide other minerals / keep other minerals constant ; 13 temperature ; 14 pH / salinity ; 15 volume of water / solution / volume of tanks ; 16 carbon dioxide ; Question Answer Marks 6 method and techniques (m) max 3 from: 17 (use of) pipettes / syringe / measuring cylinder (to measure volumes) ; 18 (use of) water-bath to maintain temperature / AW ; 19 (use of) balance to weigh algae ; 20 (use of) oven to dry algae ; 21 (use of) sodium hydrogen carbonate as source of carbon dioxide ; analysis (a) max 2 from: 22 replicates / several repeats and calculate mean / identify anomalies / outliers / identify if errors had occurred ; 23 calculation of rate as (change of) mass over time / AW ; 24 correct statistical test ; 25 plot graph of rate of growth / mass, against concentration of ammonium nitrate / AW ;
This question in 9693/41 May/June 2022
Q13 · Desalination plants are industrial facilities that produce fresh water from sea water 9693/42 May/June 2022
1 Desalination plants are industrial facilities that produce fresh water from sea water. A group of students investigated the effect of a desalination plant on the salinity of sea water and the percentage cover of the seabed with seagrass. They measured the salinity of the sea water and percentage cover of the seabed with seagrass every 5 m from the desalination plant over a total distance of 30 m. The results are shown in Table 1.1. Table 1.1 distance from desalination salinity of sea water / ppt percentage cover of plant / m seabed with seagrass 5 45 25 10 41 27 15 34 58 20 33 85 25 32 95 30 32 95 (a) (i) Draw a graph to show how the salinity of the sea water and percentage cover of the seabed with seagrass change with distance from the desalination plant. Join your points with ruled, straight lines. [5] (ii) Use your graph and Table 1.1 to suggest an explanation for the distribution of the seagrass. … … … … [2] (b) Outline how salmon perform osmoregulation in regions of high salinity. … … … … … … [3] [Total: 10]
10 marks
Mark scheme: 1(a)(i) linear axes that use at least one y axis scale half the grid ; all axes labelled ; plots correct ; points joined by straight lines ; key for both lines / labelled lines; 5 1(a)(ii) any 2 from: seagrass cannot live in areas with high salinity / less seagrass grows in areas with high salinity / seagrass cannot live in areas of concentrated brine / ORA ; high salinity / water near desalination plant, has a low water potential ; water is lost from seagrass cells (by osmosis) / cells lose turgidity / AW ; toxins are released from desalination plant / AW ; 2 1(b) any 3 from: salmon body (cells) have higher water potential than seawater so lose water (by osmosis) ; salmon drink water ; excrete / release, salt / AW ; produce concentrated urine ; active pumping (of salt) into water ; 3
This question in 9693/42 May/June 2022
Q14 · The effect of mercury from untreated sewage released into the ocean was investigated 9693/42 May/June 2022
2 The effect of mercury from untreated sewage released into the ocean was investigated. Table 2.1 shows the mean concentrations of mercury in the body tissues of species of fish with different diets that live in areas where untreated sewage is released. Table 2.1 diet of fish mean concentration of mercury in body tissues of fish / μg g–1 plants 72 small invertebrates 122 plants and invertebrates 97 small fish 382 mixed small and large fish 453 dead fish 597 (a) Use Table 2.1 to suggest an explanation for the different mean concentrations of mercury in the body tissues of fish with different diets. … … … … … … … … [4] (b) (i) Tuna have a diet of mixed small and large fish. Many health authorities advise pregnant women to eat no more than 340 g of tuna each week. Use Table 2.1 to calculate the mass of mercury found in 340 g of tuna. Give your answer to three significant figures. … μg [2] (ii) Suggest why pregnant women are advised to restrict the amount of tuna in their diet. … … … … [2] [Total: 8]
8 marks
Mark scheme: 2(a) any 4 from: mercury passes along food chains / AW ; mercury of is not broken down / bioaccumulation / excreted ; biomagnification occurs (of mercury through the food chains / trophic levels) / mercury builds up ; fish from higher trophic levels / fish that eat other fish / predators, have higher levels of mercury / fish that consume dead organisms have high levels / ORA ; dead fish may have high concentrations which killed them / were predator species / AW ; plants obtain mercury from substrate / do not obtain mercury from other trophic levels / do not feed on other organisms ; 2(b)(i) 154 000 (g) ;; 2 Question Answer Marks 2(b)(ii) any 2 from: tuna are top predators / high trophic levels / at top of food chain and accumulate mercury / have high concentrations of mercury ; mercury could harm baby / is toxic / nervous system problems / AW ; mercury concentration in baby would be high (due to smaller size of baby) / what is safe for adult is not for baby 2
This question in 9693/42 May/June 2022
Q15 · Lionfish are a species of carnivorous fish naturally found in the Pacific Ocean near… 9693/42 May/June 2022
5 Lionfish are a species of carnivorous fish naturally found in the Pacific Ocean near Indonesia. Lionfish are now found in the western Atlantic Ocean and Caribbean Sea and are classed as an invasive species. (a) State what is meant by an invasive species, as defined by the IUCN. … … [1] (b) Fig. 5.1 shows the change in population of lionfish between 2004 and 2010 on an area of coral reef near the Bahamas in the western Atlantic Ocean. 50 45 40 35 mean 30 number of lionfish 25 counted per survey 20 15 10 5 0 2004 2005 2006 2007 2008 2009 2010 year Fig. 5.1 (i) Suggest explanations for the changes in population of lionfish on this coral reef between 2004 and 2010 shown in Fig. 5.1. … … … … … … [3] (ii) Fig. 5.1 has error bars that represent the standard deviation. Explain what the standard deviations in Fig. 5.1 show about the data. … … … … [2] (c) Fig. 5.2 shows the percentage change in abundance of other species of fish and algae growing on the same coral reef between 2004 and 2010. The species of fish were classed as: • small fish species that are prey of lionfish • small fish species that are not prey of lionfish • large fish species that are competitors of lionfish • large fish species that are not competitors of lionfish +100 +80 +60 +40 +20 percentage change 0 in abundance –20 –40 –60 –80 –100 small prey small non-prey large large algae species species competitor non-competitor species species Fig. 5.2 Discuss the change in abundance of the different species of fish and algae shown in Fig. 5.2. … … … … … … [3] (d) Scientists investigated the effect of removing lionfish on the population of damselfish on a reef. Divers physically removed lionfish from an area of reef each week for a period of six months. The population of damselfish on the reef was then recorded. The population of damselfish on an area of identical reef where lionfish were not removed was also recorded. Both reefs had the same initial populations of damselfish. The scientists carried out a chi-squared test to see if removing the lionfish caused a change in the population of damselfish. They made the following null hypothesis: Removing the lionfish did not affect the number of damselfish on the reef. The results are shown in Table 5.1. Table 5.1 reef area number of expected (O – E) (O – E)2 (O – E)2 damselfish number of E (O) damselfish (E) lionfish 420 390 30 900 2.308 removed no lionfish 360 390 removed (i) Complete Table 5.1. [1] (ii) Use the formula to calculate the chi-squared value for the results. (O – E)2 chi-squared = Σ E Σ = sum of (total) O = observed values E = expected values … [1]
11 marks
Mark scheme: 5(a)(i) a species that has been introduced outside its natural past or present distribution and has become problematic / AW ; 1 5(b)(i) any 3 from: between 2004 and 2006 / up to 2006, (slow population increase) as lionfish, adapt to area / have few to breed / take time to establish / AW ; from 2004, increase as lionfish have abundant food / few predators / high breeding rate / outcompete other species / AW ; plenty of niches available for lionfish ; from 2007 / 2008 population stabilises / levels off / falls, due to competition / as food limiting / predators arrive / control methods / harvesting / AW ; 3 Question Answer Marks 5(b)(ii) any 2 from: wide variation in number of lionfish sightings in years between 2007 and 2010 ; less / little variation in number of lionfish sightings in years 2004 / 2005 / 2006 ; no overlap between 2006 and 2007 shows (significant) difference / AW ; overlap between 2007 and 2010 shows no (significant) difference / AW ; 2 5(c) any 3 from: decrease in (small) prey species as they are eaten / predated (by lionfish) ; increase in (small) non-prey species due to less competition (from other fish) / more algae to eat ; large competitors decrease as lionfish consume food / take territory / AW ; large non-competitors show similar numbers so maintain niche / are unaffected / have enough food ; algae increases, as small herbivores / small prey species, are, consumed / are fewer ; 3 5(d)(i) Reef area Number of damselfish (O) Expected number of damselfish (E) (O–E) (O–E)2 2 ( ) O E E Lionfish removed 420 390 30 900 2.308 No lionfish removed 360 390 –30 900 2.308 ; 1 5(d)(ii) 4.616 ; 1 5(d)(iii) any 3 from: the null hypothesis is rejected ; there is a significant difference (in the number of damselfish) ; the calculated value is greater than the critical value ; correct reference to 3.841 / critical value for 0.05 and 1 degree of freedom ; there is a probability of less than, 0.05 / 5, that the difference is due to chance ; 3 Question Answer Marks 5(d)(iv) any 2 from: marine ecosystems are large ; species cross (national) national borders ; species are migratory / breed in different locations ; ocean currents move species / pollutants around the globe / AW ; trade of species occurs between countries / ref to trade restrictions ; some areas of ocean / High Seas have no national ownership 2
This question in 9693/42 May/June 2022
Q16 · Desalination plants are industrial facilities that produce fresh water from sea water 9693/43 May/June 2022
1 Desalination plants are industrial facilities that produce fresh water from sea water. A group of students investigated the effect of a desalination plant on the salinity of sea water and the percentage cover of the seabed with seagrass. They measured the salinity of the sea water and percentage cover of the seabed with seagrass every 5 m from the desalination plant over a total distance of 30 m. The results are shown in Table 1.1. Table 1.1 distance from desalination salinity of sea water / ppt percentage cover of plant / m seabed with seagrass 5 45 25 10 41 27 15 34 58 20 33 85 25 32 95 30 32 95 (a) (i) Draw a graph to show how the salinity of the sea water and percentage cover of the seabed with seagrass change with distance from the desalination plant. Join your points with ruled, straight lines. [5] (ii) Use your graph and Table 1.1 to suggest an explanation for the distribution of the seagrass. … … … … [2] (b) Outline how salmon perform osmoregulation in regions of high salinity. … … … … … … [3] [Total: 10]
10 marks
Mark scheme: 1(a)(i) linear axes that use at least one y axis scale half the grid ; all axes labelled ; plots correct ; points joined by straight lines ; key for both lines / labelled lines; 5 1(a)(ii) any 2 from: seagrass cannot live in areas with high salinity / less seagrass grows in areas with high salinity / seagrass cannot live in areas of concentrated brine / ORA ; high salinity / water near desalination plant, has a low water potential ; water is lost from seagrass cells (by osmosis) / cells lose turgidity / AW ; toxins are released from desalination plant / AW ; 2 1(b) any 3 from: salmon body (cells) have higher water potential than seawater so lose water (by osmosis) ; salmon drink water ; excrete / release, salt / AW ; produce concentrated urine ; active pumping (of salt) into water ; 3
This question in 9693/43 May/June 2022
Q17 · The effect of mercury from untreated sewage released into the ocean was investigated 9693/43 May/June 2022
2 The effect of mercury from untreated sewage released into the ocean was investigated. Table 2.1 shows the mean concentrations of mercury in the body tissues of species of fish with different diets that live in areas where untreated sewage is released. Table 2.1 diet of fish mean concentration of mercury in body tissues of fish / μg g–1 plants 72 small invertebrates 122 plants and invertebrates 97 small fish 382 mixed small and large fish 453 dead fish 597 (a) Use Table 2.1 to suggest an explanation for the different mean concentrations of mercury in the body tissues of fish with different diets. … … … … … … … … [4] (b) (i) Tuna have a diet of mixed small and large fish. Many health authorities advise pregnant women to eat no more than 340 g of tuna each week. Use Table 2.1 to calculate the mass of mercury found in 340 g of tuna. Give your answer to three significant figures. … μg [2] (ii) Suggest why pregnant women are advised to restrict the amount of tuna in their diet. … … … … [2] [Total: 8]
8 marks
Mark scheme: 2(a) any 4 from: mercury passes along food chains / AW ; mercury of is not broken down / bioaccumulation / excreted ; biomagnification occurs (of mercury through the food chains / trophic levels) / mercury builds up ; fish from higher trophic levels / fish that eat other fish / predators, have higher levels of mercury / fish that consume dead organisms have high levels / ORA ; dead fish may have high concentrations which killed them / were predator species / AW ; plants obtain mercury from substrate / do not obtain mercury from other trophic levels / do not feed on other organisms ; 2(b)(i) 154 000 (g) ;; 2 Question Answer Marks 2(b)(ii) any 2 from: tuna are top predators / high trophic levels / at top of food chain and accumulate mercury / have high concentrations of mercury ; mercury could harm baby / is toxic / nervous system problems / AW ; mercury concentration in baby would be high (due to smaller size of baby) / what is safe for adult is not for baby ; 2
This question in 9693/43 May/June 2022
Q18 · Lionfish are a species of carnivorous fish naturally found in the Pacific Ocean near… 9693/43 May/June 2022
5 Lionfish are a species of carnivorous fish naturally found in the Pacific Ocean near Indonesia. Lionfish are now found in the western Atlantic Ocean and Caribbean Sea and are classed as an invasive species. (a) State what is meant by an invasive species, as defined by the IUCN. … … [1] (b) Fig. 5.1 shows the change in population of lionfish between 2004 and 2010 on an area of coral reef near the Bahamas in the western Atlantic Ocean. 50 45 40 35 mean 30 number of lionfish 25 counted per survey 20 15 10 5 0 2004 2005 2006 2007 2008 2009 2010 year Fig. 5.1 (i) Suggest explanations for the changes in population of lionfish on this coral reef between 2004 and 2010 shown in Fig. 5.1. … … … … … … [3] (ii) Fig. 5.1 has error bars that represent the standard deviation. Explain what the standard deviations in Fig. 5.1 show about the data. … … … … [2] (c) Fig. 5.2 shows the percentage change in abundance of other species of fish and algae growing on the same coral reef between 2004 and 2010. The species of fish were classed as: • small fish species that are prey of lionfish • small fish species that are not prey of lionfish • large fish species that are competitors of lionfish • large fish species that are not competitors of lionfish +100 +80 +60 +40 +20 percentage change 0 in abundance –20 –40 –60 –80 –100 small prey small non-prey large large algae species species competitor non-competitor species species Fig. 5.2 Discuss the change in abundance of the different species of fish and algae shown in Fig. 5.2. … … … … … … [3] (d) Scientists investigated the effect of removing lionfish on the population of damselfish on a reef. Divers physically removed lionfish from an area of reef each week for a period of six months. The population of damselfish on the reef was then recorded. The population of damselfish on an area of identical reef where lionfish were not removed was also recorded. Both reefs had the same initial populations of damselfish. The scientists carried out a chi-squared test to see if removing the lionfish caused a change in the population of damselfish. They made the following null hypothesis: Removing the lionfish did not affect the number of damselfish on the reef. The results are shown in Table 5.1. Table 5.1 reef area number of expected (O – E) (O – E)2 (O – E)2 damselfish number of E (O) damselfish (E) lionfish 420 390 30 900 2.308 removed no lionfish 360 390 removed (i) Complete Table 5.1. [1] (ii) Use the formula to calculate the chi-squared value for the results. (O – E)2 chi-squared = Σ E Σ = sum of (total) O = observed values E = expected values … [1]
11 marks
Mark scheme: 5(a)(i) a species that has been introduced outside its natural past or present distribution and has become problematic / AW ; 1 5(b)(i) any 3 from: between 2004 and 2006 / up to 2006, (slow population increase) as lionfish, adapt to area / have few to breed / take time to establish / AW ; from 2004, increase as lionfish have abundant food / few predators / high breeding rate / outcompete other species / AW ; plenty of niches available for lionfish ; from 2007 / 2008 population stabilises / levels off / falls, due to competition / as food limiting / predators arrive / control methods / harvesting / AW ; 3 Question Answer Marks 5(b)(ii) any 2 from: wide variation in number of lionfish sightings in years between 2007 and 2010 ; less / little variation in number of lionfish sightings in years 2004 / 2005 / 2006 ; no overlap between 2006 and 2007 shows (significant) difference / AW ; overlap between 2007 and 2010 shows no (significant) difference / AW ; 2 5(c) any 3 from: decrease in (small) prey species as they are eaten / predated (by lionfish) ; increase in (small) non-prey species due to less competition (from other fish) / more algae to eat ; large competitors decrease as lionfish consume food / take territory / AW ; large non-competitors show similar numbers so maintain niche / are unaffected / have enough food ; algae increases, as small herbivores / small prey species, are, consumed / are fewer ; 3 5(d)(i) Reef area Number of damselfish (O) Expected number of damselfish (E) (O–E) (O–E)2 2 ( ) O E E Lionfish removed 420 390 30 900 2.308 No lionfish removed 360 390 –30 900 2.308 ; 1 5(d)(ii) 4.616 ; 1 5(d)(iii) any 3 from: the null hypothesis is rejected ; there is a significant difference (in the number of damselfish) ; the calculated value is greater than the critical value ; correct reference to 3.841 / critical value for 0.05 and 1 degree of freedom ; there is a probability of less than, 0.05 / 5, that the difference is due to chance ; 3 Question Answer Marks 5(d)(iv) any 2 from: marine ecosystems are large ; species cross (national) national borders ; species are migratory / breed in different locations ; ocean currents move species / pollutants around the globe / AW ; trade of species occurs between countries / ref to trade restrictions ; some areas of ocean / High Seas have no national ownership ; 2
This question in 9693/43 May/June 2022
Q19 · Plastics and microplastics can have a major impact on the marine environment 9693/41 Oct/Nov 2022
4 Plastics and microplastics can have a major impact on the marine environment. (a) Explain why microplastics absorbed by plankton may pose a risk to humans. … … … … … … [3] (b) A survey into the effect of discarded fishing gear on coral reefs was carried out in the sea around Thailand. Areas of coral reefs were identified that had discarded fishing gear lying on top of them (above) or by the sides (adjacent). Each area of reef with discarded fishing gear was assessed for damage. The results are shown in Table 4.1. Table 4.1 type of discarded number of reefs that were number of reefs that were not fishing gear on damaged damaged reef gear above gear adjacent gear above gear adjacent nets 193 174 49 719 ropes 14 10 5 59 nylon lines 18 18 75 114 (i) Calculate the total number of reefs that had nets found adjacent to them. … [1] (ii) Use your answer to (b)(i) and Table 4.1 to calculate the percentage of reefs with nets adjacent to them that were damaged. … % [1] (iii) Use Table 4.1 to assess the threats posed to coral reefs by different types of discarded fishing gear. … … … … … … … … [4] (iv) Suggest two ways in which the survey could be improved to compare which of the discarded items had the largest impact on the coral reefs. 1 … … 2 … … [2] (v) Suggest one other impact that discarded fishing gear has on the marine environment. … … [1] [Total: 12]
12 marks
Mark scheme: 4(a) any 3 from: 3 toxic chemicals are absorbed onto the microplastics ; (toxins / microplastics) pass along food chain / are biomagnified along food chain / fish at top of food chain have high concentrations ; humans eat fish, that are high up food chain / have high toxin concentrations / that eat plankton / AW ; microplastics / toxins, are not excreted / broken down / removed from bodies / bioaccumulate ; 4(b)(i) 719 + 174 = 893 ; 1 4(b)(ii) 174 / 893 100 = 19.48(%) / 19.5 ; 1 4(b)(iii) any 4 from: 4 nets are most damaging / pose most risk ; 32% of reefs with nets were damaged ; nets are the most common type of gear found on the reefs / nets most discarded ; ropes are the least common type of discarded gear ; nets made up 78% of the discarded gear when found on or near reefs ; nets / ropes, which are on top of reefs are more damaging than when adjacent ; nylon lines are least damaging ; nylon lines caused 16% damage to reefs where they were found ; 4(b)(iv) any 2 from: 2 compare damage to reefs with no fishing gear on them ; standardise ages of reef ; measure distance on reef from adjacent gear ; standardise sizes / percentage cover, of fishing gear / quantify amount of fishing gear ; standardise types / area, of coral / state which coral species are damaged ; record weather patterns / standardise temperatures / investigate different seasons / etc. ; quantify the damage ; examine other areas of reef (away from Thailand) ; state if reefs have more than one type of gear ; 4(b)(v) any 1 from: 1 fish / turtles / dolphins / birds / AW, become trapped / damaged ; ingested / eaten by fish / turtles / AW ; block light reaching reef ; release toxins ;
This question in 9693/41 Oct/Nov 2022
Q20 · Plastics and microplastics can have a major impact on the marine environment 9693/42 Oct/Nov 2022
4 Plastics and microplastics can have a major impact on the marine environment. (a) Explain why microplastics absorbed by plankton may pose a risk to humans. … … … … … … [3] (b) A survey into the effect of discarded fishing gear on coral reefs was carried out in the sea around Thailand. Areas of coral reefs were identified that had discarded fishing gear lying on top of them (above) or by the sides (adjacent). Each area of reef with discarded fishing gear was assessed for damage. The results are shown in Table 4.1. Table 4.1 type of discarded number of reefs that were number of reefs that were not fishing gear on damaged damaged reef gear above gear adjacent gear above gear adjacent nets 193 174 49 719 ropes 14 10 5 59 nylon lines 18 18 75 114 (i) Calculate the total number of reefs that had nets found adjacent to them. … [1] (ii) Use your answer to (b)(i) and Table 4.1 to calculate the percentage of reefs with nets adjacent to them that were damaged. … % [1] (iii) Use Table 4.1 to assess the threats posed to coral reefs by different types of discarded fishing gear. … … … … … … … … [4] (iv) Suggest two ways in which the survey could be improved to compare which of the discarded items had the largest impact on the coral reefs. 1 … … 2 … … [2] (v) Suggest one other impact that discarded fishing gear has on the marine environment. … … [1] [Total: 12]
12 marks
Mark scheme: 4(a) any 3 from: 3 toxic chemicals are absorbed onto the microplastics ; (toxins / microplastics) pass along food chain / are biomagnified along food chain / fish at top of food chain have high concentrations ; humans eat fish, that are high up food chain / have high toxin concentrations / that eat plankton / AW ; microplastics / toxins, are not excreted / broken down / removed from bodies / bioaccumulate ; 4(b)(i) 719 + 174 = 893 ; 1 4(b)(ii) 174 / 893 100 = 19.48(%) / 19.5 ; 1 4(b)(iii) any 4 from: 4 nets are most damaging / pose most risk ; 32% of reefs with nets were damaged ; nets are the most common type of gear found on the reefs / nets most discarded ; ropes are the least common type of discarded gear ; nets made up 78% of the discarded gear when found on or near reefs ; nets / ropes, which are on top of reefs are more damaging than when adjacent ; nylon lines are least damaging ; nylon lines caused 16% damage to reefs where they were found ; 4(b)(iv) any 2 from: 2 compare damage to reefs with no fishing gear on them ; standardise ages of reef ; measure distance on reef from adjacent gear ; standardise sizes / percentage cover, of fishing gear / quantify amount of fishing gear ; standardise types / area, of coral / state which coral species are damaged ; record weather patterns / standardise temperatures / investigate different seasons / etc. ; quantify the damage ; examine other areas of reef (away from Thailand) ; state if reefs have more than one type of gear ; 4(b)(v) any 1 from: 1 fish / turtles / dolphins / birds / AW, become trapped / damaged ; ingested / eaten by fish / turtles / AW ; block light reaching reef ; release toxins ;
This question in 9693/42 Oct/Nov 2022
Q21 · Plastics and microplastics can have a major impact on the marine environment 9693/43 Oct/Nov 2022
4 Plastics and microplastics can have a major impact on the marine environment. (a) Explain why microplastics absorbed by plankton may pose a risk to humans. … … … … … … [3] (b) A survey into the effect of discarded fishing gear on coral reefs was carried out in the sea around Thailand. Areas of coral reefs were identified that had discarded fishing gear lying on top of them (above) or by the sides (adjacent). Each area of reef with discarded fishing gear was assessed for damage. The results are shown in Table 4.1. Table 4.1 type of discarded number of reefs that were number of reefs that were not fishing gear on damaged damaged reef gear above gear adjacent gear above gear adjacent nets 193 174 49 719 ropes 14 10 5 59 nylon lines 18 18 75 114 (i) Calculate the total number of reefs that had nets found adjacent to them. … [1] (ii) Use your answer to (b)(i) and Table 4.1 to calculate the percentage of reefs with nets adjacent to them that were damaged. … % [1] (iii) Use Table 4.1 to assess the threats posed to coral reefs by different types of discarded fishing gear. … … … … … … … … [4] (iv) Suggest two ways in which the survey could be improved to compare which of the discarded items had the largest impact on the coral reefs. 1 … … 2 … … [2] (v) Suggest one other impact that discarded fishing gear has on the marine environment. … … [1] [Total: 12]
12 marks
Mark scheme: 4(a) any 3 from: 3 toxic chemicals are absorbed onto the microplastics ; (toxins / microplastics) pass along food chain / are biomagnified along food chain / fish at top of food chain have high concentrations ; humans eat fish, that are high up food chain / have high toxin concentrations / that eat plankton / AW ; microplastics / toxins, are not excreted / broken down / removed from bodies / bioaccumulate ; 4(b)(i) 719 + 174 = 893 ; 1 4(b)(ii) 174 / 893 100 = 19.48(%) / 19.5 ; 1 4(b)(iii) any 4 from: 4 nets are most damaging / pose most risk ; 32% of reefs with nets were damaged ; nets are the most common type of gear found on the reefs / nets most discarded ; ropes are the least common type of discarded gear ; nets made up 78% of the discarded gear when found on or near reefs ; nets / ropes, which are on top of reefs are more damaging than when adjacent ; nylon lines are least damaging ; nylon lines caused 16% damage to reefs where they were found ; 4(b)(iv) any 2 from: 2 compare damage to reefs with no fishing gear on them ; standardise ages of reef ; measure distance on reef from adjacent gear ; standardise sizes / percentage cover, of fishing gear / quantify amount of fishing gear ; standardise types / area, of coral / state which coral species are damaged ; record weather patterns / standardise temperatures / investigate different seasons / etc. ; quantify the damage ; examine other areas of reef (away from Thailand) ; state if reefs have more than one type of gear ; 4(b)(v) any 1 from: 1 fish / turtles / dolphins / birds / AW, become trapped / damaged ; ingested / eaten by fish / turtles / AW ; block light reaching reef ; release toxins ;
This question in 9693/43 Oct/Nov 2022
Q22 · Describe how microplastics are formed 9693/41 May/June 2023
5 (a) Describe how microplastics are formed. … … … … [2] (b) A scientist investigated the effect of human population density near coastal areas on the number of microplastic particles in the sand of 12 beaches. The scientist made the following null hypothesis: There is no correlation between human population density and the number of microplastic particles. They carried out a Spearman’s rank correlation test on their data. Table 5.1 shows some of their calculations. Table 5.1 human r1, number of r2, D D2 population rank of microplastic rank of (r1 – r2) density / people human particles number of per km2 population per 250 cm3 microplastic density sand particles 0 1 5 1 0 0 5 2 7 3 –1 1 10 3.5 19 6 –2.5 6.25 15 5 6 2 3 9 155 11 85 11 0 0 75 8.5 75 9.5 –1 1 65 7 25 7 0 0 75 … 65 8 … … 10 3.5 11 4.5 –1 1 20 6 11 4.5 1.5 2.25 120 10 75 9.5 0.5 0.25 175 12 115 12 0 0 ∑ D2 = … (i) Complete Table 5.1 by determining the missing values. Write your answers in Table 5.1. [2] (ii) Use the formula to calculate the Spearman’s rank correlation coefficient for the data in Table 5.1. 6 × ∑D 2 rS = 1 – n3 – n rS = Spearman’s rank correlation coefficient ∑ = sum of (total) D = difference in rank between each pair of measurements n = number of pairs of items in the sample rS = … [1] (iii) Table 5.2 is a critical values table for Spearman’s rank correlation coefficient. Table 5.2 number of pairs, n rS (p < 0.05) 5 1.000 6 0.886 7 0.786 8 0.738 9 0.700 10 0.648 11 0.618 12 0.587 13 0.560 14 0.538 15 0.521 Use your calculated value from (b)(ii), and Table 5.2, to assess whether the null hypothesis can be accepted or rejected. … … … … … … [3] (c) Use the information in this question to suggest why regularly eating mussels from shores near areas with high human population density may be harmful to humans. … … … … [2] [Total: 10]
10 marks
Mark scheme: 5(a) any 2 of: 1 plastic broken into pieces of less than 5 mm ; 2 due to action of UV (radiation) ; 3 due to wave (action) ; 4 due to high temperature ; 5 due to wind (action) ; 2 Question Answer Marks 5(b)(i) human population density / people per km2 r1, rank of human population density number of microplastic particles per 250 cm3 sand r2, rank of number of microplastic particles D (r1 – r2) D2 0 1 5 1 0 0 5 2 7 3 –1 1 10 3.5 19 6 –2.5 6.25 15 5 6 2 3 9 155 11 85 11 0 0 75 8.5 75 9.5 –1 1 65 7 25 7 0 0 75 8.5 65 8 0.5 0.25 ; 10 3.5 11 4.5 –1 1 20 6 11 4.5 1.5 2.25 120 10 75 9.5 0.5 0.25 175 12 115 12 0 0 2 D 21 ; 2 5(b)(ii) 0.93 ; 1 Question Answer Marks 5(b)(iii) any 3 of: the null hypothesis is rejected ; the calculated value is greater than the critical value ; critical value is 0.587 ; there is a significant positive correlation / there is a significant association between human population and microplastic density ; 3 5(c) any 2 of: (area with high human populations have) high densities of microplastic / AW ; microplastics absorb toxins / AW ; mussels, take in / eat, microplastics ; humans get toxins from eating mussels / humans get microplastics from eating mussels / AW ; 2
This question in 9693/41 May/June 2023
Q23 · An area of coral reef had been damaged by pollution from agricultural run‑off containing… 9693/42 May/June 2023
3 An area of coral reef had been damaged by pollution from agricultural run‑off containing fertiliser over a number of years. In 1990 the percentage of this coral reef covered with live, unbleached coral was measured. In 1995, this coral reef was placed inside a marine protected area (MPA). The use of fertiliser by local agriculture was banned. The percentage of coral reef covered with live, unbleached coral, and the Simpson’s index of diversity for the coral reef were measured every five years. The results are shown in Table 3.1. Table 3.1 year percentage of reef covered Simpson’s index of diversity with live, unbleached coral 1990 37 0.43 1995 35 0.41 2000 41 0.42 2005 45 0.48 2010 62 0.51 2015 85 0.57 (a) Explain how fertiliser in agricultural run‑off can damage coral reefs. … … … … … … … … [4] (ii) Suggest why Simpson’s index of diversity changed between 1995 and 2015. … … … … … … [3] (iii) Explain one reason why it is not possible to be certain that the recovery of the coral reef was caused by the banning of fertiliser use. … … … … [2] [Total: 14]
14 marks
Mark scheme: 3(a) any 4 of: 1 fertiliser contains nitrates / phosphates / AW ; 2 algal blooms / eutrophication / AW ; 3 reducing light intensity / increased turbidity / AW ; 4 less photosynthesis (by zooxanthellae / phytoplankton / algae) ; 5 less glucose for coral / equivalent ; 6 death / decomposition, of algae / AW ; 7 reduced oxygen / hypoxia, (due to bacterial respiration) ; 8 less (coral) respiration ; 3 (b)(i) two linear y-axis scales using more than half grid ; plots correct ; all axes labelled ; points joined with ruled, straight lines with no extrapolation / bars neat and even spaces between ; lines or bars labelled / AW ; 5 Question Answer Marks 3(b)(ii) any 3 of: 1. (increased coral growth) increases primary productivity of reef / more energy fixed / more carbon fixed ; 2. increased, number of species / species richness ; 3. more food for (consumer) organisms ; 4. more niches available / habitats / shelter / AW ; 5. more food chains / AW ; 6. more nursery sites / AW ; 7. (and) increased balanced number of species / AW ; 3 3(b)(iii) any 2 of: idea of correlation does not mean causation / AW ; has not been compared with an area of reef not in MPA / there is no control area / area may still have pollution (from other sources) ; regrowth (of coral) could be due to other factors / AW ; 2
This question in 9693/42 May/June 2023
Q24 · Copepods are marine zooplankton 9693/42 May/June 2023
5 Copepods are marine zooplankton. They are crustaceans that have a complex life cycle. (a) Explain the advantages of having a complex life cycle. … … … … [2] (b) Algae grow on the surfaces of microplastics when microplastics are left in ocean surface water for over one month. The presence of the algae causes some animals to mistake the microplastic for food. Scientists measured the consumption of microplastic particles by copepod larvae, adult female copepods and adult male copepods. They counted the number of these consumed microplastic particles that were: • new, with no algae growing on them • two months old, with algae growing on them. The results are shown in Fig. 5.1. 16 newnew microplasticmicroplastic 14 two-month-oldtwo-month-old microplasticmicroplastic 12 number of 10 consumed microplastic 8 particles per copepod 6 4 2 0 larvae adult females adult males copepod group Fig. 5.1 (i) Describe the effect of age of the microplastics on their consumption by the different groups of copepod. … … … … … … [3] (ii) Salmon are grown for human consumption, using aquaculture in sea cages. Waste food from the salmon aquaculture is broken down by microorganisms, causing algal blooms. Copepods are small enough to swim into salmon cages and are eaten by salmon. Use this information and the information in Fig. 5.1 to suggest why the presence of microplastics in the waters around salmon aquaculture systems poses a threat to humans. … … … … … … [3] (iii) Plastic sheets placed into sea water gradually break down to form microplastics. As the plastic sheet breaks down, its area decreases. Temperature and wave action are two of the factors that affect the breakdown of plastic sheets into microplastics. Plan a laboratory‑based investigation that you could do to investigate the effect of water temperature on the rate of breakdown of plastic sheets. You are provided with standard laboratory apparatus and materials. Your plan should: • include a clear statement of the hypothesis • identify the independent, dependent and standardised variables • include full details of the method so that another person can follow it • describe how you would analyse your results • be safe and ethical. … … … … … … … … … … … … … … … …
8 marks
Mark scheme: 5(a) any 2 of: idea of additional stages / larval stage ; for distribution / live in different habitats ; to consume different food source / not compete with adults / AW ; 5(b)(i) any 3 of: 1 more two-month-old / older microplastic (with algal growth) are consumed (by all copepod groups) ; 2 largest increase for male copepods (between new and old) / smallest increase for larvae / AW ; 3 adults consume more than larvae / larvae consume the least / ORA ; 4 correct manipulation of data ; 5 more new microplastics are consumed by the females / least new microplastic consumed by larvae ; 3 5(b)(ii) any 3 of: 1 food breaks down / decomposes, to release mineral ions / named mineral ion ; 2 algae grow due to high mineral ion concentration / AW ; 3 (large amounts of) algae will attach to the microplastics / AW ; 4 microplastics absorb toxins ; 5 copepods eat (large amounts of) microplastic (when covered with algae) / AW ; 6 salmon will consume copepods that contain microplastics / toxins will accumulate in salmon / bioaccumulation / biomagnification / AW ; 3 Question Answer Marks 5(b)(iii) clear statement of hypothesis: increasing temperature will increase rate of / reduce time taken for, breakdown / AW ; AND any 10 of: independent variable 1 independent variable identified as temperature ; 2 using a range of at least five temperatures, stated or range given ; dependent variable 3 dependent variable identified as measuring loss of / change in, mass / length / area, of plastic ; 4 description of how to measure change over a stated time ; standardised variables MAX 4 of: 5 same size / type of plastic / same mass / area, of plastic ; 6 same light intensity / UV / AW ; 7 same movement of water / AW ; 8 same volume of water / AW ; 9 same salinity / AW ; 10 same acidity / carbon dioxide / other correct variable / AW ; 11 Question Answer Marks 5(b)(iii) Safety and ethics 11 safe / ethical disposal of plastic ; 12 eye protection with pH buffers / salinity / care with heating apparatus / statement of low-risk experiment ; Analysis MAX 3 of: 13 repeat at least three times and calculate means / medians / averages ; 14 plot graph of rate / change in mass / AW vs. temperature ; 15 correct named statistical test (e.g. Spearman’s rank) / standard deviation / error bars ; 16 calculate rate as change / time taken ; 17 results table with headings ;
This question in 9693/42 May/June 2023
Q25 · An area of coral reef had been damaged by pollution from agricultural run‑off containing… 9693/43 May/June 2023
3 An area of coral reef had been damaged by pollution from agricultural run‑off containing fertiliser over a number of years. In 1990 the percentage of this coral reef covered with live, unbleached coral was measured. In 1995, this coral reef was placed inside a marine protected area (MPA). The use of fertiliser by local agriculture was banned. The percentage of coral reef covered with live, unbleached coral, and the Simpson’s index of diversity for the coral reef were measured every five years. The results are shown in Table 3.1. Table 3.1 year percentage of reef covered Simpson’s index of diversity with live, unbleached coral 1990 37 0.43 1995 35 0.41 2000 41 0.42 2005 45 0.48 2010 62 0.51 2015 85 0.57 (a) Explain how fertiliser in agricultural run‑off can damage coral reefs. … … … … … … … … [4] (ii) Suggest why Simpson’s index of diversity changed between 1995 and 2015. … … … … … … [3] (iii) Explain one reason why it is not possible to be certain that the recovery of the coral reef was caused by the banning of fertiliser use. … … … … [2] [Total: 14]
14 marks
Mark scheme: 3(a) any 4 of: 1 fertiliser contains nitrates / phosphates / AW ; 2 algal blooms / eutrophication / AW ; 3 reducing light intensity / increased turbidity / AW ; 4 less photosynthesis (by zooxanthellae / phytoplankton / algae) ; 5 less glucose for coral / equivalent ; 6 death / decomposition, of algae / AW ; 7 reduced oxygen / hypoxia, (due to bacterial respiration) ; 8 less (coral) respiration ; 3 (b)(i) two linear y-axis scales using more than half grid ; plots correct ; all axes labelled ; points joined with ruled, straight lines with no extrapolation / bars neat and even spaces between ; lines or bars labelled / AW ; 5 Question Answer Marks 3(b)(ii) any 3 of: 1. (increased coral growth) increases primary productivity of reef / more energy fixed / more carbon fixed ; 2. increased, number of species / species richness ; 3. more food for (consumer) organisms ; 4. more niches available / habitats / shelter / AW ; 5. more food chains / AW ; 6. more nursery sites / AW ; 7. (and) increased balanced number of species / AW ; 3 3(b)(iii) any 2 of: idea of correlation does not mean causation / AW ; has not been compared with an area of reef not in MPA / there is no control area / area may still have pollution (from other sources) ; regrowth (of coral) could be due to other factors / AW ; 2
This question in 9693/43 May/June 2023
Q26 · Copepods are marine zooplankton 9693/43 May/June 2023
5 Copepods are marine zooplankton. They are crustaceans that have a complex life cycle. (a) Explain the advantages of having a complex life cycle. … … … … [2] (b) Algae grow on the surfaces of microplastics when microplastics are left in ocean surface water for over one month. The presence of the algae causes some animals to mistake the microplastic for food. Scientists measured the consumption of microplastic particles by copepod larvae, adult female copepods and adult male copepods. They counted the number of these consumed microplastic particles that were: • new, with no algae growing on them • two months old, with algae growing on them. The results are shown in Fig. 5.1. 16 newnew microplasticmicroplastic 14 two-month-oldtwo-month-old microplasticmicroplastic 12 number of 10 consumed microplastic 8 particles per copepod 6 4 2 0 larvae adult females adult males copepod group Fig. 5.1 (i) Describe the effect of age of the microplastics on their consumption by the different groups of copepod. … … … … … … [3] (ii) Salmon are grown for human consumption, using aquaculture in sea cages. Waste food from the salmon aquaculture is broken down by microorganisms, causing algal blooms. Copepods are small enough to swim into salmon cages and are eaten by salmon. Use this information and the information in Fig. 5.1 to suggest why the presence of microplastics in the waters around salmon aquaculture systems poses a threat to humans. … … … … … … [3] (iii) Plastic sheets placed into sea water gradually break down to form microplastics. As the plastic sheet breaks down, its area decreases. Temperature and wave action are two of the factors that affect the breakdown of plastic sheets into microplastics. Plan a laboratory‑based investigation that you could do to investigate the effect of water temperature on the rate of breakdown of plastic sheets. You are provided with standard laboratory apparatus and materials. Your plan should: • include a clear statement of the hypothesis • identify the independent, dependent and standardised variables • include full details of the method so that another person can follow it • describe how you would analyse your results • be safe and ethical. … … … … … … … … … … … … … … … …
8 marks
Mark scheme: 5(a) any 2 of: idea of additional stages / larval stage ; for distribution / live in different habitats ; to consume different food source / not compete with adults / AW ; 5(b)(i) any 3 of: 1 more two-month-old / older microplastic (with algal growth) are consumed (by all copepod groups) ; 2 largest increase for male copepods (between new and old) / smallest increase for larvae / AW ; 3 adults consume more than larvae / larvae consume the least / ORA ; 4 correct manipulation of data ; 5 more new microplastics are consumed by the females / least new microplastic consumed by larvae ; 3 5(b)(ii) any 3 of: 1 food breaks down / decomposes, to release mineral ions / named mineral ion ; 2 algae grow due to high mineral ion concentration / AW ; 3 (large amounts of) algae will attach to the microplastics / AW ; 4 microplastics absorb toxins ; 5 copepods eat (large amounts of) microplastic (when covered with algae) / AW ; 6 salmon will consume copepods that contain microplastics / toxins will accumulate in salmon / bioaccumulation / biomagnification / AW ; 3 Question Answer Marks 5(b)(iii) clear statement of hypothesis: increasing temperature will increase rate of / reduce time taken for, breakdown / AW ; AND any 10 of: independent variable 1 independent variable identified as temperature ; 2 using a range of at least five temperatures, stated or range given ; dependent variable 3 dependent variable identified as measuring loss of / change in, mass / length / area, of plastic ; 4 description of how to measure change over a stated time ; standardised variables MAX 4 of: 5 same size / type of plastic / same mass / area, of plastic ; 6 same light intensity / UV / AW ; 7 same movement of water / AW ; 8 same volume of water / AW ; 9 same salinity / AW ; 10 same acidity / carbon dioxide / other correct variable / AW ; 11 Question Answer Marks 5(b)(iii) Safety and ethics 11 safe / ethical disposal of plastic ; 12 eye protection with pH buffers / salinity / care with heating apparatus / statement of low-risk experiment ; Analysis MAX 3 of: 13 repeat at least three times and calculate means / medians / averages ; 14 plot graph of rate / change in mass / AW vs. temperature ; 15 correct named statistical test (e.g. Spearman’s rank) / standard deviation / error bars ; 16 calculate rate as change / time taken ; 17 results table with headings ;
This question in 9693/43 May/June 2023
Q27 · Desalination plants are industrial factories that produce fresh water from sea water 9693/41 Oct/Nov 2023
1 Desalination plants are industrial factories that produce fresh water from sea water. Fig. 1.1 shows a photograph of a desalination plant. Fig. 1.1 Desalination plants are thought to be harmful to seagrass beds due to the release of highly saline water into the sea. (a) Fig. 1.2 is a diagram of a cell from a seagrass leaf. cell wall mitochondrion nucleus rough endoplasmic reticulum Golgi body A B chloroplast X smooth endoplasmic reticulum Fig. 1.2 (i) Name the organelle labelled X and state its function. name … function … … [2] (ii) The diagram has a magnification of × 30 000. Calculate the actual width of the seagrass cell between A and B on the diagram. Show your working. State the unit. … [3] (b) Scientists investigated the possible impact of desalination plants on seagrasses. They grew seagrass in water of different salinities and measured: • the percentage water content of the seagrass cells • the water potential of the seagrass cells. The percentage water content of the seagrass cells and the water potential of the seagrass cells were measured at the start, after four weeks and after six weeks. Water potential was measured in kilopascals, kPa. The results are shown in Fig. 1.3 and Fig. 1.4. 90 Key 80 start 70 4 weeks 60 6 weeks percentage water 50 content of cells 40 30 20 10 0 35 37 46 54 salinity of water / ppt Fig. 1.3 0 Key start –1000 4 weeks –2000 6 weeks water potential –3000 / kPa –4000 –5000 –6000 35 37 46 54 salinity of water / ppt Fig. 1.4 (i) Use the data in Fig. 1.3 to describe the effect of growing the seagrass in water of different salinities. … … … … … … [3] (ii) Use the data in Fig. 1.3 and Fig. 1.4 to explain the changes in water potential over time when the seagrass is placed into water of 54 ppt salinity. … … … … … … [3] (c) Desalination plants also release toxic heavy metal ions into the sea water. Explain why the release of heavy metal ions is harmful for top predator organisms in ecosystems. … … … … … … [3] [Total: 14]
14 marks
Mark scheme: Question Answer Marks 1(a)(i) (large) (permanent) vacuole ; 2 store sap / salts / water / sugars / nutrients / AW : 1(a)(ii) length measured ; 3 divide length by 30 000 ; convert to magnitude of units and unit, (m or mm) ; 1(b)(i) any 3 of: 3 1 no change / little change, in percentage water content at 35 (ppt), 37 (ppt) and 46 (ppt) ; 2 decrease at 54 (ppt) ; 3 ref to overlap of error bars ; 4 (at 54 ppt) decrease after four and at six weeks / continues to decrease over time ; 5 credit correct manipulated data ; 1(b)(ii) any 3 of: 3 1 water moves out (of cells) ; 2 by osmosis ; 3 because water potential was higher inside / moves down a water potential gradient / ORA ; 4 concentration of, solute / salts / AW, in cells increases ; 5 so that water potential decreases (in cells) ; 6 more water is removed (at 54 ppt) over time ; 1(c) any 3 of: 3 1 metal ions are taken up by producers / filter feeders / low trophic levels / AW ; 2 metal ions are, not excreted / stored in tissues / bioaccumulation occurs / AW ; 3 concentration of metal ions increases along the food chain / biomagnification occurs / AW ; 4 death of producers / lower trophic level organisms results in less food / less energy in ecosystem / damage to food chains / AW ; 5 ref to how metal ions damage organisms ;
This question in 9693/41 Oct/Nov 2023
Q28 · Salmon are grown commercially around coastal areas using extensive aquaculture systems… 9693/41 Oct/Nov 2023
3 Salmon are grown commercially around coastal areas using extensive aquaculture systems called salmon farms. (a) Outline the process of salmon aquaculture in extensive systems. … … … … … … … … [4] (b) Scientists investigated the escape of salmon from salmon farms into the wild. Farmed salmon are fed food pellets that contain a dye. The dye accumulates in the body tissues of the salmon. Salmon were caught by rod-and-line from rivers and areas of sea close to a salmon farm. Salmon that had escaped from the salmon farm were identified by the presence of the dye in their body tissues. Fig. 3.1 shows the percentage of female salmon caught that had escaped from the salmon farm from 2000 to 2005. 90 80 70 60 percentage of 50female salmon caught that had escaped 40 30 20 10 0 2000 2001 2002 2003 2004 2005 year Fig. 3.1 (i) In 2005, a total of 53 female salmon were caught. Use Fig. 3.1 to calculate the number of female salmon caught that had escaped from the salmon farm. … [1] (ii) Suggest why the percentage of female salmon caught that had escaped increased from 2000 to 2005. … … … … [2] (c) In the wild, salmon lay eggs in the upstream areas of rivers. They lay the eggs in nests called redds. In 2005, the scientists investigated the presence of eggs produced by escaped salmon in rivers near the salmon farm. The scientists also took samples of the fertilised eggs and determined the percentage that hatched and developed into fish fry. They identified the eggs from female salmon that had escaped by the presence of the food dye. They also measured the range of concentration of dye in the eggs from each redd. The results are shown in Table 3.1. Table 3.1 redds number percentage of eggs range of dye of redds that developed into concentration in eggs fish fry redds with eggs containing dye 9 83 3.6% to 55% redds with eggs not containing dye 11 98 N/A (i) Suggest a reason for the range of dye concentration in the eggs laid by the escaped salmon. … … [1] (ii) Discuss the impacts of the escaped salmon on the wild salmon populations. Use the information in Fig. 3.1 and Table 3.1 to support your answer. … … … … … … … … [4] (iii) Suggest why the information in Table 3.1 may be insufficient to make a firm conclusion on the impact of escaped salmon on wild salmon populations. … … … … [2] [Total: 14]
14 marks
Mark scheme: 3(a) any 4 of: 4 1 brood salmon are used to produce eggs and sperm / AW ; 2 eggs / small fish / fry / alevins, kept in (indoor), hatcheries / tanks ; 3 transfer to, cages / nets, in sea / outdoors / AW ; 4 keep large and small fish apart / separate by age / AW ; 5 add feed / add feed pellets / AW ; 6 use of pesticides / antibiotics / vaccinations / AW ; 7 prevent predator action / AW ; 8 ocean currents supply oxygen / food / remove waste ; 3(b)(i) (82 / 100 53 =) 43 ; 1 3(b)(ii) any 2 of: 2 1 salmon live for more than one year / AW ; 2 more salmon escape each year / AW ; 3 damage to the cages / bad weather disrupting the cages / cages get larger holes over time / AW ; 4 number of wild salmon is decreasing / AW ; 5 increased number of salmon farms / more stock kept / AW ; 6 credit reason for decrease in number of wild salmon / AW ; 3(c)(i) any 1 of: 1 1 salmon that have lived for several years outside the farm will have less dye in body / will have been eating more wild food / AW ; 2 recently escaped salmon will have higher dye concentrations ; 3 egg sizes vary (so concentration varies) / wild salmon fertilised salmon so dye reduced ; 4 different amounts of dye were given to salmon when in the farm / some salmon ate more food when in the farm ; 3(c)(ii) any 4 of: 4 1 escaped salmon are able to breed / reproduce / AW ; 2 but egg viability / hatching rate is lower than wild salmon / do not develop as well as wild salmon / AW ; 3 escaped salmon breed for several years ; 4 shown by the wide range of dye in eggs ; 5 escaped salmon outcompeting wild salmon / consume more food / AW ; 6 wild salmon may lose breeding sites / habitats / AW ; 7 fewer wild salmon survive / proportion of wild salmon are decreasing / AW ; 8 salmon may pass on disease to the wild salmon ; 9 escaped salmon affect the gene pool / reduce genetic diversity / have weaker alleles / AW ; 3(c)(iii) any 2 of: 2 1 a very small sample size has been used / not enough data / AW ; 2 no mention of how many eggs, develop / produced (as it is a percentage) / redds may have different numbers of eggs / AW ; 3 the wild salmon may breed in different areas (compared with escaped) / no clear information about locations / no information about size of habitat / no information about distances escaped salmon travel / AW ; 4 the dye colour may be lost from eggs / salmon after several years very wide difference in dye concentration / dye is not passed on into adults from eggs / AW ; 5 no data about disease or genetics of salmon ; 6 no direct data to show how wild salmon populations have changed / correlation does not show causation / AW ;
This question in 9693/41 Oct/Nov 2023
Q29 · The rate of photosynthesis of producer organisms can be affected by many abiotic and… 9693/41 Oct/Nov 2023
5 The rate of photosynthesis of producer organisms can be affected by many abiotic and biotic factors. (a) The light-dependent stage of photosynthesis occurs in the lamellae of chloroplasts. (i) Give the two products of the light-dependent stage that are used in the light-independent stage. 1 … 2 … [2] (ii) Fig. 5.1 shows the absorption spectra for the photosynthetic pigments extracted from two different species of alga, species A and species B. 1 species B species A relative absorption 0 400 450 500 550 600 650 700 750 blue green red wavelength / nm Fig. 5.1 Use Fig. 5.1 to explain which one of the two species of alga is adapted to live in deeper water. … … … … [2] (b) Atrazine is a weedkiller used in agriculture in some parts of the world. Atrazine is a toxic chemical that inhibits the light-dependent stage of photosynthesis. There have been concerns that atrazine can cause pollution due to its being washed into rivers and coastal waters. Plan a laboratory investigation that you could do to investigate the effect of changing the concentration of weedkiller on the rate of photosynthesis of an aquatic plant. You are provided with a 1% stock solution of atrazine. Your plan should: • include a clear statement of the hypothesis • identify the independent, dependent and standardised variables • include full details of the method so that another person can follow it • describe how you would analyse your results • be safe and ethical. … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … [11] [Total: 15] The boundaries and names shown, the designations used and the presentation of material on any maps contained in this question paper/insert do not imply official endorsement or acceptance by Cambridge Assessment International Education concerning the legal status of any country, territory, or area or any of its authorities, or of the delimitation of its frontiers or boundaries.
15 marks
Mark scheme: 5(a)(i) reduced NADP / NADPH / NADPH2 ; 2 ATP ; 5(a)(ii) any 2 of: 2 (species A) because it can absorb more light / green light, between 510 nm and 640 nm ; red light / longer wavelength light, is not available in deeper water / AW / ORA ; so (species A) has, accessory pigments / fucoxanthin, (as well as chlorophyll) (that absorbs in the 510 nm to 640 nm range); 5(b) hypothesis 11 1 photosynthesis (rate) / (rate of) oxygen production, will decrease as weedkiller concentration increases / AW ; and any 10 of: independent variable 2 identified as concentration of atrazine ; 3 use of at least 5 different concentrations in range of up to 1% ; dependent variable 4 identified as rate of photosynthesis / rate of oxygen production / AW ; 5 ref to method of measuring dependent variable in set time ; standardised variables max 3 6 same volume of water / same salinity of water ; 7 constant temperature ; 8 pH ; 9 same size / volume / mass of plant ; 10 light intensity / wavelength / lamp placed at set distance from plant / AW ; 11 same volume / concentration of hydrogencarbonate solution / same carbon dioxide / AW ; 5(b) method max 3 12 method to make dilutions ; 13 ref to placing shoot of plant cut end uppermost in boiling tube / beaker ; 14 ref to using paperclip to weigh down plant / AW ; 15 ref to using 0% or water to replace atrazine as a control experiment ; 16 ref to using a heat shield between lamp and plant / use water bath ; 17 use of pH buffer solutions ; analysis max 3 18 ref to replicating experiment 3 times and calculating means / medians ; 19 method for calculating the rate of photosynthesis ; 20 plot graph of rate of photosynthesis against concentration ; 21 ref to suitable named statistical test e.g. Spearman’s rank ; 22 correct example of results table with headings ; safety and ethics 23 atrazine is toxic so, use eye protection / use gloves / wash spills / pH buffers are irritants so use eye protection / gloves ; 24 do not wash down sink / AW, due to environmental impacts / do not take large amounts of plants from the wild / AW ;
This question in 9693/41 Oct/Nov 2023
Q30 · Desalination plants are industrial factories that produce fresh water from sea water 9693/42 Oct/Nov 2023
1 Desalination plants are industrial factories that produce fresh water from sea water. Fig. 1.1 shows a photograph of a desalination plant. Fig. 1.1 Desalination plants are thought to be harmful to seagrass beds due to the release of highly saline water into the sea. (a) Fig. 1.2 is a diagram of a cell from a seagrass leaf. cell wall mitochondrion nucleus rough endoplasmic reticulum Golgi body A B chloroplast X smooth endoplasmic reticulum Fig. 1.2 (i) Name the organelle labelled X and state its function. name … function … … [2] (ii) The diagram has a magnification of × 30 000. Calculate the actual width of the seagrass cell between A and B on the diagram. Show your working. State the unit. … [3] (b) Scientists investigated the possible impact of desalination plants on seagrasses. They grew seagrass in water of different salinities and measured: • the percentage water content of the seagrass cells • the water potential of the seagrass cells. The percentage water content of the seagrass cells and the water potential of the seagrass cells were measured at the start, after four weeks and after six weeks. Water potential was measured in kilopascals, kPa. The results are shown in Fig. 1.3 and Fig. 1.4. 90 Key 80 start 70 4 weeks 60 6 weeks percentage water 50 content of cells 40 30 20 10 0 35 37 46 54 salinity of water / ppt Fig. 1.3 0 Key start –1000 4 weeks –2000 6 weeks water potential –3000 / kPa –4000 –5000 –6000 35 37 46 54 salinity of water / ppt Fig. 1.4 (i) Use the data in Fig. 1.3 to describe the effect of growing the seagrass in water of different salinities. … … … … … … [3] (ii) Use the data in Fig. 1.3 and Fig. 1.4 to explain the changes in water potential over time when the seagrass is placed into water of 54 ppt salinity. … … … … … … [3] (c) Desalination plants also release toxic heavy metal ions into the sea water. Explain why the release of heavy metal ions is harmful for top predator organisms in ecosystems. … … … … … … [3] [Total: 14]
14 marks
Mark scheme: Question Answer Marks 1(a)(i) (large) (permanent) vacuole ; 2 store sap / salts / water / sugars / nutrients / AW : 1(a)(ii) length measured ; 3 divide length by 30 000 ; convert to magnitude of units and unit, (m or mm) ; 1(b)(i) any 3 of: 3 1 no change / little change, in percentage water content at 35 (ppt), 37 (ppt) and 46 (ppt) ; 2 decrease at 54 (ppt) ; 3 ref to overlap of error bars ; 4 (at 54 ppt) decrease after four and at six weeks / continues to decrease over time ; 5 credit correct manipulated data ; 1(b)(ii) any 3 of: 3 1 water moves out (of cells) ; 2 by osmosis ; 3 because water potential was higher inside / moves down a water potential gradient / ORA ; 4 concentration of, solute / salts / AW, in cells increases ; 5 so that water potential decreases (in cells) ; 6 more water is removed (at 54 ppt) over time ; 1(c) any 3 of: 3 1 metal ions are taken up by producers / filter feeders / low trophic levels / AW ; 2 metal ions are, not excreted / stored in tissues / bioaccumulation occurs / AW ; 3 concentration of metal ions increases along the food chain / biomagnification occurs / AW ; 4 death of producers / lower trophic level organisms results in less food / less energy in ecosystem / damage to food chains / AW ; 5 ref to how metal ions damage organisms ;
This question in 9693/42 Oct/Nov 2023
Q31 · Salmon are grown commercially around coastal areas using extensive aquaculture systems… 9693/42 Oct/Nov 2023
3 Salmon are grown commercially around coastal areas using extensive aquaculture systems called salmon farms. (a) Outline the process of salmon aquaculture in extensive systems. … … … … … … … … [4] (b) Scientists investigated the escape of salmon from salmon farms into the wild. Farmed salmon are fed food pellets that contain a dye. The dye accumulates in the body tissues of the salmon. Salmon were caught by rod-and-line from rivers and areas of sea close to a salmon farm. Salmon that had escaped from the salmon farm were identified by the presence of the dye in their body tissues. Fig. 3.1 shows the percentage of female salmon caught that had escaped from the salmon farm from 2000 to 2005. 90 80 70 60 percentage of 50female salmon caught that had escaped 40 30 20 10 0 2000 2001 2002 2003 2004 2005 year Fig. 3.1 (i) In 2005, a total of 53 female salmon were caught. Use Fig. 3.1 to calculate the number of female salmon caught that had escaped from the salmon farm. … [1] (ii) Suggest why the percentage of female salmon caught that had escaped increased from 2000 to 2005. … … … … [2] (c) In the wild, salmon lay eggs in the upstream areas of rivers. They lay the eggs in nests called redds. In 2005, the scientists investigated the presence of eggs produced by escaped salmon in rivers near the salmon farm. The scientists also took samples of the fertilised eggs and determined the percentage that hatched and developed into fish fry. They identified the eggs from female salmon that had escaped by the presence of the food dye. They also measured the range of concentration of dye in the eggs from each redd. The results are shown in Table 3.1. Table 3.1 redds number percentage of eggs range of dye of redds that developed into concentration in eggs fish fry redds with eggs containing dye 9 83 3.6% to 55% redds with eggs not containing dye 11 98 N/A (i) Suggest a reason for the range of dye concentration in the eggs laid by the escaped salmon. … … [1] (ii) Discuss the impacts of the escaped salmon on the wild salmon populations. Use the information in Fig. 3.1 and Table 3.1 to support your answer. … … … … … … … … [4] (iii) Suggest why the information in Table 3.1 may be insufficient to make a firm conclusion on the impact of escaped salmon on wild salmon populations. … … … … [2] [Total: 14]
14 marks
Mark scheme: 3(a) any 4 of: 4 1 brood salmon are used to produce eggs and sperm / AW ; 2 eggs / small fish / fry / alevins, kept in (indoor), hatcheries / tanks ; 3 transfer to, cages / nets, in sea / outdoors / AW ; 4 keep large and small fish apart / separate by age / AW ; 5 add feed / add feed pellets / AW ; 6 use of pesticides / antibiotics / vaccinations / AW ; 7 prevent predator action / AW ; 8 ocean currents supply oxygen / food / remove waste ; 3(b)(i) (82 / 100 53 =) 43 ; 1 3(b)(ii) any 2 of: 2 1 salmon live for more than one year / AW ; 2 more salmon escape each year / AW ; 3 damage to the cages / bad weather disrupting the cages / cages get larger holes over time / AW ; 4 number of wild salmon is decreasing / AW ; 5 increased number of salmon farms / more stock kept / AW ; 6 credit reason for decrease in number of wild salmon / AW ; 3(c)(i) any 1 of: 1 1 salmon that have lived for several years outside the farm will have less dye in body / will have been eating more wild food / AW ; 2 recently escaped salmon will have higher dye concentrations ; 3 egg sizes vary (so concentration varies) / wild salmon fertilised salmon so dye reduced ; 4 different amounts of dye were given to salmon when in the farm / some salmon ate more food when in the farm ; 3(c)(ii) any 4 of: 4 1 escaped salmon are able to breed / reproduce / AW ; 2 but egg viability / hatching rate is lower than wild salmon / do not develop as well as wild salmon / AW ; 3 escaped salmon breed for several years ; 4 shown by the wide range of dye in eggs ; 5 escaped salmon outcompeting wild salmon / consume more food / AW ; 6 wild salmon may lose breeding sites / habitats / AW ; 7 fewer wild salmon survive / proportion of wild salmon are decreasing / AW ; 8 salmon may pass on disease to the wild salmon ; 9 escaped salmon affect the gene pool / reduce genetic diversity / have weaker alleles / AW ; 3(c)(iii) any 2 of: 2 1 a very small sample size has been used / not enough data / AW ; 2 no mention of how many eggs, develop / produced (as it is a percentage) / redds may have different numbers of eggs / AW ; 3 the wild salmon may breed in different areas (compared with escaped) / no clear information about locations / no information about size of habitat / no information about distances escaped salmon travel / AW ; 4 the dye colour may be lost from eggs / salmon after several years very wide difference in dye concentration / dye is not passed on into adults from eggs / AW ; 5 no data about disease or genetics of salmon ; 6 no direct data to show how wild salmon populations have changed / correlation does not show causation / AW ;
This question in 9693/42 Oct/Nov 2023
Q32 · The rate of photosynthesis of producer organisms can be affected by many abiotic and… 9693/42 Oct/Nov 2023
5 The rate of photosynthesis of producer organisms can be affected by many abiotic and biotic factors. (a) The light-dependent stage of photosynthesis occurs in the lamellae of chloroplasts. (i) Give the two products of the light-dependent stage that are used in the light-independent stage. 1 … 2 … [2] (ii) Fig. 5.1 shows the absorption spectra for the photosynthetic pigments extracted from two different species of alga, species A and species B. 1 species B species A relative absorption 0 400 450 500 550 600 650 700 750 blue green red wavelength / nm Fig. 5.1 Use Fig. 5.1 to explain which one of the two species of alga is adapted to live in deeper water. … … … … [2] (b) Atrazine is a weedkiller used in agriculture in some parts of the world. Atrazine is a toxic chemical that inhibits the light-dependent stage of photosynthesis. There have been concerns that atrazine can cause pollution due to its being washed into rivers and coastal waters. Plan a laboratory investigation that you could do to investigate the effect of changing the concentration of weedkiller on the rate of photosynthesis of an aquatic plant. You are provided with a 1% stock solution of atrazine. Your plan should: • include a clear statement of the hypothesis • identify the independent, dependent and standardised variables • include full details of the method so that another person can follow it • describe how you would analyse your results • be safe and ethical. … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … [11] [Total: 15] The boundaries and names shown, the designations used and the presentation of material on any maps contained in this question paper/insert do not imply official endorsement or acceptance by Cambridge Assessment International Education concerning the legal status of any country, territory, or area or any of its authorities, or of the delimitation of its frontiers or boundaries.
15 marks
Mark scheme: 5(a)(i) reduced NADP / NADPH / NADPH2 ; 2 ATP ; 5(a)(ii) any 2 of: 2 (species A) because it can absorb more light / green light, between 510 nm and 640 nm ; red light / longer wavelength light, is not available in deeper water / AW / ORA ; so (species A) has, accessory pigments / fucoxanthin, (as well as chlorophyll) (that absorbs in the 510 nm to 640 nm range); 5(b) hypothesis 11 1 photosynthesis (rate) / (rate of) oxygen production, will decrease as weedkiller concentration increases / AW ; and any 10 of: independent variable 2 identified as concentration of atrazine ; 3 use of at least 5 different concentrations in range of up to 1% ; dependent variable 4 identified as rate of photosynthesis / rate of oxygen production / AW ; 5 ref to method of measuring dependent variable in set time ; standardised variables max 3 6 same volume of water / same salinity of water ; 7 constant temperature ; 8 pH ; 9 same size / volume / mass of plant ; 10 light intensity / wavelength / lamp placed at set distance from plant / AW ; 11 same volume / concentration of hydrogencarbonate solution / same carbon dioxide / AW ; 5(b) method max 3 12 method to make dilutions ; 13 ref to placing shoot of plant cut end uppermost in boiling tube / beaker ; 14 ref to using paperclip to weigh down plant / AW ; 15 ref to using 0% or water to replace atrazine as a control experiment ; 16 ref to using a heat shield between lamp and plant / use water bath ; 17 use of pH buffer solutions ; analysis max 3 18 ref to replicating experiment 3 times and calculating means / medians ; 19 method for calculating the rate of photosynthesis ; 20 plot graph of rate of photosynthesis against concentration ; 21 ref to suitable named statistical test e.g. Spearman’s rank ; 22 correct example of results table with headings ; safety and ethics 23 atrazine is toxic so, use eye protection / use gloves / wash spills / pH buffers are irritants so use eye protection / gloves ; 24 do not wash down sink / AW, due to environmental impacts / do not take large amounts of plants from the wild / AW ;
This question in 9693/42 Oct/Nov 2023
Q33 · Desalination plants are industrial factories that produce fresh water from sea water 9693/43 Oct/Nov 2023
1 Desalination plants are industrial factories that produce fresh water from sea water. Fig. 1.1 shows a photograph of a desalination plant. Fig. 1.1 Desalination plants are thought to be harmful to seagrass beds due to the release of highly saline water into the sea. (a) Fig. 1.2 is a diagram of a cell from a seagrass leaf. cell wall mitochondrion nucleus rough endoplasmic reticulum Golgi body A B chloroplast X smooth endoplasmic reticulum Fig. 1.2 (i) Name the organelle labelled X and state its function. name … function … … [2] (ii) The diagram has a magnification of × 30 000. Calculate the actual width of the seagrass cell between A and B on the diagram. Show your working. State the unit. … [3] (b) Scientists investigated the possible impact of desalination plants on seagrasses. They grew seagrass in water of different salinities and measured: • the percentage water content of the seagrass cells • the water potential of the seagrass cells. The percentage water content of the seagrass cells and the water potential of the seagrass cells were measured at the start, after four weeks and after six weeks. Water potential was measured in kilopascals, kPa. The results are shown in Fig. 1.3 and Fig. 1.4. 90 Key 80 start 70 4 weeks 60 6 weeks percentage water 50 content of cells 40 30 20 10 0 35 37 46 54 salinity of water / ppt Fig. 1.3 0 Key start –1000 4 weeks –2000 6 weeks water potential –3000 / kPa –4000 –5000 –6000 35 37 46 54 salinity of water / ppt Fig. 1.4 (i) Use the data in Fig. 1.3 to describe the effect of growing the seagrass in water of different salinities. … … … … … … [3] (ii) Use the data in Fig. 1.3 and Fig. 1.4 to explain the changes in water potential over time when the seagrass is placed into water of 54 ppt salinity. … … … … … … [3] (c) Desalination plants also release toxic heavy metal ions into the sea water. Explain why the release of heavy metal ions is harmful for top predator organisms in ecosystems. … … … … … … [3] [Total: 14]
14 marks
Mark scheme: Question Answer Marks 1(a)(i) (large) (permanent) vacuole ; 2 store sap / salts / water / sugars / nutrients / AW : 1(a)(ii) length measured ; 3 divide length by 30 000 ; convert to magnitude of units and unit, (m or mm) ; 1(b)(i) any 3 of: 3 1 no change / little change, in percentage water content at 35 (ppt), 37 (ppt) and 46 (ppt) ; 2 decrease at 54 (ppt) ; 3 ref to overlap of error bars ; 4 (at 54 ppt) decrease after four and at six weeks / continues to decrease over time ; 5 credit correct manipulated data ; 1(b)(ii) any 3 of: 3 1 water moves out (of cells) ; 2 by osmosis ; 3 because water potential was higher inside / moves down a water potential gradient / ORA ; 4 concentration of, solute / salts / AW, in cells increases ; 5 so that water potential decreases (in cells) ; 6 more water is removed (at 54 ppt) over time ; 1(c) any 3 of: 3 1 metal ions are taken up by producers / filter feeders / low trophic levels / AW ; 2 metal ions are, not excreted / stored in tissues / bioaccumulation occurs / AW ; 3 concentration of metal ions increases along the food chain / biomagnification occurs / AW ; 4 death of producers / lower trophic level organisms results in less food / less energy in ecosystem / damage to food chains / AW ; 5 ref to how metal ions damage organisms ;
This question in 9693/43 Oct/Nov 2023
Q34 · Salmon are grown commercially around coastal areas using extensive aquaculture systems… 9693/43 Oct/Nov 2023
3 Salmon are grown commercially around coastal areas using extensive aquaculture systems called salmon farms. (a) Outline the process of salmon aquaculture in extensive systems. … … … … … … … … [4] (b) Scientists investigated the escape of salmon from salmon farms into the wild. Farmed salmon are fed food pellets that contain a dye. The dye accumulates in the body tissues of the salmon. Salmon were caught by rod-and-line from rivers and areas of sea close to a salmon farm. Salmon that had escaped from the salmon farm were identified by the presence of the dye in their body tissues. Fig. 3.1 shows the percentage of female salmon caught that had escaped from the salmon farm from 2000 to 2005. 90 80 70 60 percentage of 50female salmon caught that had escaped 40 30 20 10 0 2000 2001 2002 2003 2004 2005 year Fig. 3.1 (i) In 2005, a total of 53 female salmon were caught. Use Fig. 3.1 to calculate the number of female salmon caught that had escaped from the salmon farm. … [1] (ii) Suggest why the percentage of female salmon caught that had escaped increased from 2000 to 2005. … … … … [2] (c) In the wild, salmon lay eggs in the upstream areas of rivers. They lay the eggs in nests called redds. In 2005, the scientists investigated the presence of eggs produced by escaped salmon in rivers near the salmon farm. The scientists also took samples of the fertilised eggs and determined the percentage that hatched and developed into fish fry. They identified the eggs from female salmon that had escaped by the presence of the food dye. They also measured the range of concentration of dye in the eggs from each redd. The results are shown in Table 3.1. Table 3.1 redds number percentage of eggs range of dye of redds that developed into concentration in eggs fish fry redds with eggs containing dye 9 83 3.6% to 55% redds with eggs not containing dye 11 98 N/A (i) Suggest a reason for the range of dye concentration in the eggs laid by the escaped salmon. … … [1] (ii) Discuss the impacts of the escaped salmon on the wild salmon populations. Use the information in Fig. 3.1 and Table 3.1 to support your answer. … … … … … … … … [4] (iii) Suggest why the information in Table 3.1 may be insufficient to make a firm conclusion on the impact of escaped salmon on wild salmon populations. … … … … [2] [Total: 14]
14 marks
Mark scheme: 3(a) any 4 of: 4 1 brood salmon are used to produce eggs and sperm / AW ; 2 eggs / small fish / fry / alevins, kept in (indoor), hatcheries / tanks ; 3 transfer to, cages / nets, in sea / outdoors / AW ; 4 keep large and small fish apart / separate by age / AW ; 5 add feed / add feed pellets / AW ; 6 use of pesticides / antibiotics / vaccinations / AW ; 7 prevent predator action / AW ; 8 ocean currents supply oxygen / food / remove waste ; 3(b)(i) (82 / 100 53 =) 43 ; 1 3(b)(ii) any 2 of: 2 1 salmon live for more than one year / AW ; 2 more salmon escape each year / AW ; 3 damage to the cages / bad weather disrupting the cages / cages get larger holes over time / AW ; 4 number of wild salmon is decreasing / AW ; 5 increased number of salmon farms / more stock kept / AW ; 6 credit reason for decrease in number of wild salmon / AW ; 3(c)(i) any 1 of: 1 1 salmon that have lived for several years outside the farm will have less dye in body / will have been eating more wild food / AW ; 2 recently escaped salmon will have higher dye concentrations ; 3 egg sizes vary (so concentration varies) / wild salmon fertilised salmon so dye reduced ; 4 different amounts of dye were given to salmon when in the farm / some salmon ate more food when in the farm ; 3(c)(ii) any 4 of: 4 1 escaped salmon are able to breed / reproduce / AW ; 2 but egg viability / hatching rate is lower than wild salmon / do not develop as well as wild salmon / AW ; 3 escaped salmon breed for several years ; 4 shown by the wide range of dye in eggs ; 5 escaped salmon outcompeting wild salmon / consume more food / AW ; 6 wild salmon may lose breeding sites / habitats / AW ; 7 fewer wild salmon survive / proportion of wild salmon are decreasing / AW ; 8 salmon may pass on disease to the wild salmon ; 9 escaped salmon affect the gene pool / reduce genetic diversity / have weaker alleles / AW ; 3(c)(iii) any 2 of: 2 1 a very small sample size has been used / not enough data / AW ; 2 no mention of how many eggs, develop / produced (as it is a percentage) / redds may have different numbers of eggs / AW ; 3 the wild salmon may breed in different areas (compared with escaped) / no clear information about locations / no information about size of habitat / no information about distances escaped salmon travel / AW ; 4 the dye colour may be lost from eggs / salmon after several years very wide difference in dye concentration / dye is not passed on into adults from eggs / AW ; 5 no data about disease or genetics of salmon ; 6 no direct data to show how wild salmon populations have changed / correlation does not show causation / AW ;
This question in 9693/43 Oct/Nov 2023
Q35 · The rate of photosynthesis of producer organisms can be affected by many abiotic and… 9693/43 Oct/Nov 2023
5 The rate of photosynthesis of producer organisms can be affected by many abiotic and biotic factors. (a) The light-dependent stage of photosynthesis occurs in the lamellae of chloroplasts. (i) Give the two products of the light-dependent stage that are used in the light-independent stage. 1 … 2 … [2] (ii) Fig. 5.1 shows the absorption spectra for the photosynthetic pigments extracted from two different species of alga, species A and species B. 1 species B species A relative absorption 0 400 450 500 550 600 650 700 750 blue green red wavelength / nm Fig. 5.1 Use Fig. 5.1 to explain which one of the two species of alga is adapted to live in deeper water. … … … … [2] (b) Atrazine is a weedkiller used in agriculture in some parts of the world. Atrazine is a toxic chemical that inhibits the light-dependent stage of photosynthesis. There have been concerns that atrazine can cause pollution due to its being washed into rivers and coastal waters. Plan a laboratory investigation that you could do to investigate the effect of changing the concentration of weedkiller on the rate of photosynthesis of an aquatic plant. You are provided with a 1% stock solution of atrazine. Your plan should: • include a clear statement of the hypothesis • identify the independent, dependent and standardised variables • include full details of the method so that another person can follow it • describe how you would analyse your results • be safe and ethical. … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … [11] [Total: 15] The boundaries and names shown, the designations used and the presentation of material on any maps contained in this question paper/insert do not imply official endorsement or acceptance by Cambridge Assessment International Education concerning the legal status of any country, territory, or area or any of its authorities, or of the delimitation of its frontiers or boundaries.
15 marks
Mark scheme: 5(a)(i) reduced NADP / NADPH / NADPH2 ; 2 ATP ; 5(a)(ii) any 2 of: 2 (species A) because it can absorb more light / green light, between 510 nm and 640 nm ; red light / longer wavelength light, is not available in deeper water / AW / ORA ; so (species A) has, accessory pigments / fucoxanthin, (as well as chlorophyll) (that absorbs in the 510 nm to 640 nm range); 5(b) hypothesis 11 1 photosynthesis (rate) / (rate of) oxygen production, will decrease as weedkiller concentration increases / AW ; and any 10 of: independent variable 2 identified as concentration of atrazine ; 3 use of at least 5 different concentrations in range of up to 1% ; dependent variable 4 identified as rate of photosynthesis / rate of oxygen production / AW ; 5 ref to method of measuring dependent variable in set time ; standardised variables max 3 6 same volume of water / same salinity of water ; 7 constant temperature ; 8 pH ; 9 same size / volume / mass of plant ; 10 light intensity / wavelength / lamp placed at set distance from plant / AW ; 11 same volume / concentration of hydrogencarbonate solution / same carbon dioxide / AW ; 5(b) method max 3 12 method to make dilutions ; 13 ref to placing shoot of plant cut end uppermost in boiling tube / beaker ; 14 ref to using paperclip to weigh down plant / AW ; 15 ref to using 0% or water to replace atrazine as a control experiment ; 16 ref to using a heat shield between lamp and plant / use water bath ; 17 use of pH buffer solutions ; analysis max 3 18 ref to replicating experiment 3 times and calculating means / medians ; 19 method for calculating the rate of photosynthesis ; 20 plot graph of rate of photosynthesis against concentration ; 21 ref to suitable named statistical test e.g. Spearman’s rank ; 22 correct example of results table with headings ; safety and ethics 23 atrazine is toxic so, use eye protection / use gloves / wash spills / pH buffers are irritants so use eye protection / gloves ; 24 do not wash down sink / AW, due to environmental impacts / do not take large amounts of plants from the wild / AW ;
This question in 9693/43 Oct/Nov 2023
Q36 · Aquaculture in coastal areas is used to produce large quantities of shrimp 9693/41 May/June 2024
3 Aquaculture in coastal areas is used to produce large quantities of shrimp. Shrimp aquaculture can cause environmental pollution. Scientists are researching ways to make shrimp aquaculture more environmentally sustainable. (a) (i) Outline the process for aquaculture of shrimp. … … … … … … [3] (ii) Give two strategies that can be used to help ensure the long-term success of aquaculture. 1 … … 2 … … [2] (b) Mussels are filter-feeding organisms that consume microalgae and other organic waste. Wastewater from shrimp aquaculture sites contains large amounts of ammonium ions that pollute the sea. The ammonium ions are converted to nitrate ions by bacteria. Scientists investigated the effects of growing mussels and adding microalgae on the removal of nitrate ions from wastewater produced by shrimp aquaculture. • Wastewater from a shrimp aquaculture site was collected and placed into tanks. • Different densities of mussels were added to the tanks. • The same mass of microalgae was added to each tank. • The nitrate ion concentration of the water was measured at the start and every day for the next six days. The results are shown in Fig. 3.1. 3.0 8 mussels 2.5 per square metre 2.0 nitrate ion concentration 1.5 no mussels / mg dm–3 1.0 4 mussels per square 0.5 metre 0 0 1 2 3 4 5 6 time / days Fig. 3.1 (i) Calculate the mean rate of change of nitrate ion concentration with no mussels over the six-day period. State the unit. Show your working. … [3] (ii) Describe the effects of adding different densities of mussels on the removal of nitrate ions from the water over the six-day period. … … … … … … [3] (c) The scientists also measured dissolved oxygen concentration in the water every day for the six days. The results are shown in Fig. 3.2. 12 10 8 dissolved oxygen 6 no musselsconcentration / mg dm–3 4 mussels 4 per square metre 8 mussels 2 per square metre 0 0 1 2 3 4 5 6 time / days Fig. 3.2 (i) The same mass of microalgae was added to each tank at the start. Explain the change in dissolved oxygen concentration in the water up to day three when microalgae were present with no mussels. … … … … [2] (ii) Ammonium ions are converted into nitrate ions by bacteria in the water. Nitrate ions are absorbed by algae. Mussels consume algae. Discuss the effects of adding different densities of mussels on the changes in concentration of oxygen and nitrate ions in the water. Use the information in Fig. 3.1 and Fig. 3.2 to support your answer. … … … … … … … … [4] [Total: 17]
17 marks
Mark scheme: 3(a)(i) any 3 of: 1 eggs placed / larvae grown in indoor tanks / AW ; 2 sterile conditions / AW ; 3 (postlarvae) transferred to nurseries / nursery tanks ; 4 (post)larvae / juveniles, transferred into raceway ponds / outdoor pools / natural water / growout pools / AW ; 5 feed / algae provided / AW ; 6 AVP ; 3(a)(ii) any 2 of: 1 availability of stock / AW ; 2 availability of clean water / water purification / remove wastes / AW ; 3 availability of feed / AW ; 4 efficiency of use of feed / use high quality feed / AW ; 5 availability of labour / AW ; 6 disease management / AW ; 7 availability of location / space / AW ; 8 (market) demand / AW ; 9 access to markets / transport / AW ; 10 return on investment / profit making / money to reinvest / AW ; 2 3(b)(i) 0.083 ;; (two marks) 2(.00) – 1.5(0) or 1.5 – 2 or 0.5 or ÷ 6 (for one mark only) mg dm-3 day-1 ; 3 3(b)(ii) any 3 of: 1 with no mussels, there is a (steady) decrease ; 2 with four mussels there is a greater / steeper / AW, decrease ; 3 with eight mussels there is decrease up to 2 days and then an increase ; 4 correctly manipulated data ; 3 Question Answer Marks 3(c)(i) any 2 of: 1 algae photosynthesise ; 2 photosynthesis / algae, produce / release oxygen ; 3 algae increase in population (as they absorb nitrate ions) ; 4 no / less, respiration (from mussels) (to remove oxygen) ; 2 3(c)(ii) any 4 of: 1 oxygen decreases more with 8 mussels / AW ; 2 nitrate increases with 8 mussels / AW ; 3 more / many algae consumed / AW, with 8 mussels ; 4 less nitrate removed / absorbed by algae (with 8 mussels) ; 5 faeces / waste, decomposes / decays / AW ; 6 respiration (by mussels / bacteria) removes oxygen ; 7 less photosynthesis to release oxygen with 8 mussels ; 4
This question in 9693/41 May/June 2024
Q37 · Some barnacles and a dogwhelk on a rock 9693/41 Oct/Nov 2024
1 Fig. 1.1 shows some barnacles and a dogwhelk on a rock. Fig. 1.1 Adult barnacles are sessile and are often found attached to rocks on rocky shores. Barnacles have a complex life cycle with planktonic larvae. (a) Explain why a complex life cycle is an advantage for sessile organisms. … … … … [2] (b) The dogwhelk feeds on barnacles on rocky shores. Scientists investigated whether the settlement of barnacles on a rocky shore was affected by: • the presence of dogwhelks • the quantity of phytoplankton in the sea water next to the shore. The scientists placed 0.25 m2 plastic tiles onto four rocky shores: • one shore with a high quantity of phytoplankton in the sea and with dogwhelks present • one shore with a high quantity of phytoplankton in the sea and with no dogwhelks present • one shore with a low quantity of phytoplankton in the sea and with dogwhelks present • one shore with a low quantity of phytoplankton in the sea and with no dogwhelks present. All the tiles had a central area which dogwhelks could not access. Fig. 1.2 shows one of the tiles used. central area covered with mesh to stop dogwhelks getting in plastic tile Fig. 1.2 The plastic tiles were examined after two months. The population densities of the barnacles growing in the central area which dogwhelks could not access were calculated. (i) The central area of one plastic tile had 12 barnacles settled in an area of 0.0225 m2. Calculate the population density of barnacles for this plastic tile as the number of barnacles per m2. Give your answer to three significant figures. … per m2 [2] Fig. 1.3 shows the population density of barnacles that had settled on the plastic tiles on all four rocky shores. Key dogwhelks present dogwhelks not present 800 700 600 500 number of barnacles 400 per square metre 300 200 100 0 low quantities of high quantities of phytoplankton phytoplankton rocky shore Fig. 1.3 (ii) Summarise the results of the investigation shown in Fig. 1.3. … … … … [2] (iii) The scientists concluded that there was a strong probability that the presence of dogwhelks affects the settlement of barnacles onto rocks. Discuss the extent to which the error bars for standard deviation shown in Fig. 1.3 support the scientists’ conclusion. … … … … [2] (iv) Suggest explanations for the effect of dogwhelks and quantities of phytoplankton on the settling of the barnacles. … … … … … … [3] (c) The acorn barnacle has spread all around the world on ships and is now considered to be an invasive species. (i) Explain why invasive species are a risk to ecosystems. … … … … … … [3] (ii) It has been suggested that introducing dogwhelks into new areas colonised by acorn barnacles could be a method of control. Suggest a possible negative consequence of introducing dogwhelks into areas with acorn barnacles. … … [1] [Total: 15]
15 marks
Mark scheme: Question Answer Marks 1(a) any 2 of: 2 allows dispersal to wider area / other areas / moves to different locations / AW ; to reduce competition / larvae have different niches from adults / AW ; allows (larvae to) feed on plankton / AW ; 1(b)(i) 533 (to 3 sig figs) ;; 2 1(b)(ii) more barnacles are found on the shores where there are more phytoplankton / ORA ; 2 more barnacles where there are no dogwhelks / ORA ; 1(b)(iii) any 2 of: 2 supported because no overlap (with and without dogwhelks) on shore with low quantities of phytoplankton / AW ; less support as there is an overlap (with and without dogwhelks) with larger quantities of phytoplankton / AW ; other factors may be affecting result / correlation not causal ; 1(b)(iv) any 3 of: 3 barnacles consume phytoplankton / more food for barnacles (if more phytoplankton) / ORA / AW ; so more survival of larvae ; dogwhelks reduces, attachment / settling, of barnacle larvae ; due to presence of, chemicals / scent, from dogwhelks / AW ; less reproduction of barnacles (to reduce population) (when dogwhelks present / less phytoplankton) / AW ; 1(c)(i) any 3 of: 3 lack predators so increase in population / AW ; overconsume prey / AW ; out compete native species / AW ; AVP ; 1(c)(ii) may become an invasive species itself / may have no predator / consume other native species / AW ; 1
This question in 9693/41 Oct/Nov 2024
Q38 · Agriculture poses a threat to coral reefs in many parts of the world due to the run-off… 9693/41 Oct/Nov 2024
3 Agriculture poses a threat to coral reefs in many parts of the world due to the run-off of fertilisers and herbicides into the sea. (a) Explain how fertiliser run-off can pose a threat to coral reefs. … … … … … … [3] (b) Herbicides are chemicals that are used to kill weeds on farmland. Scientists investigated the effect of herbicides on the production of ATP, the production of reduced NADP and the rate of carbon fixation by dinoflagellates. Suspensions of chloroplasts taken from dinoflagellates were placed into a test-tube in bright light. The concentrations of ATP, reduced NADP and glucose were measured at time 0. Herbicide was added to the test-tube and the concentrations of ATP, reduced NADP and glucose were measured after 10 minutes, 20 minutes and 30 minutes. The results are shown in Table 3.1. Table 3.1 time / min concentration of ATP concentration of concentration of / arbitrary units reduced NADP glucose / arbitrary units / arbitrary units 0 25 21 15 10 15 15 15 20 10 5 10 30 10 1 5 (i) Compare the change in concentration of ATP with the change in the concentration of reduced NADP over the 30-minute period. … … … … [2] (ii) The herbicide reduces the concentration of chlorophyll in the chloroplasts of dinoflagellates. Explain the effect of adding herbicide on the changes in concentration of ATP and reduced NADP shown in Table 3.1. … … … … … … [3] (iii) Explain the effect of adding herbicide on the change in concentration of glucose shown in Table 3.1. … … … … … … [3] (c) Marine diatoms are planktonic producers. Fig. 3.1 shows a photograph of some marine diatoms. Fig. 3.1 Make a large drawing of the part of the diatom shown inside the box in Fig. 3.1. Do not label your diagram. [4] [Total: 15]
15 marks
Mark scheme: 3(a) any 3 of: 3 1 release of nitrogen / phosphorus ; 2 (increased) algal growth / algal blooms / eutrophication / AW ; 3 (covering coral so) reducing light intensity / AW ; 4 reducing photosynthesis (of coral) / reducing (primary) productivity / AW ; 5 (increased) decomposition ; 6 loss of oxygen ; 7 AVP ; 3(b)(i) any 2 of: 2 both decrease ; ATP levels off / reduced NADP continues to fall / AW ; greater fall in NADP than ATP / ORA / AW ; 3(b)(ii) any 3 of: 3 less light-dependent stage ; less light trapped by chlorophyll / less photoactivation of chlorophyll / AW ; less transfer of energy from, light / chlorophyll, to ATP / reduced NADP ; some ATP continues to be produced via respiration ; AVP ; 3(b)(iii) any 3 of: 3 glucose concentration falls / AW ; light-independent stage does not occur ; due to loss of ATP / reduced NADP ; less fixation of carbon / AW ; glucose is used in respiration ; glucose is converted to starch / organic molecules / other named substance ; 3(c) lines are thin, clear, unbroken and no shading ; 4 at least one third of space used ; correct proportions of cell width, length and chloroplasts ; correct detail ; correct number of chloroplasts (minimum of 8) + double line for cell wall ;
This question in 9693/41 Oct/Nov 2024
Q39 · Some barnacles and a dogwhelk on a rock 9693/42 Oct/Nov 2024
1 Fig. 1.1 shows some barnacles and a dogwhelk on a rock. Fig. 1.1 Adult barnacles are sessile and are often found attached to rocks on rocky shores. Barnacles have a complex life cycle with planktonic larvae. (a) Explain why a complex life cycle is an advantage for sessile organisms. … … … … [2] (b) The dogwhelk feeds on barnacles on rocky shores. Scientists investigated whether the settlement of barnacles on a rocky shore was affected by: • the presence of dogwhelks • the quantity of phytoplankton in the sea water next to the shore. The scientists placed 0.25 m2 plastic tiles onto four rocky shores: • one shore with a high quantity of phytoplankton in the sea and with dogwhelks present • one shore with a high quantity of phytoplankton in the sea and with no dogwhelks present • one shore with a low quantity of phytoplankton in the sea and with dogwhelks present • one shore with a low quantity of phytoplankton in the sea and with no dogwhelks present. All the tiles had a central area which dogwhelks could not access. Fig. 1.2 shows one of the tiles used. central area covered with mesh to stop dogwhelks getting in plastic tile Fig. 1.2 The plastic tiles were examined after two months. The population densities of the barnacles growing in the central area which dogwhelks could not access were calculated. (i) The central area of one plastic tile had 12 barnacles settled in an area of 0.0225 m2. Calculate the population density of barnacles for this plastic tile as the number of barnacles per m2. Give your answer to three significant figures. … per m2 [2] Fig. 1.3 shows the population density of barnacles that had settled on the plastic tiles on all four rocky shores. Key dogwhelks present dogwhelks not present 800 700 600 500 number of barnacles 400 per square metre 300 200 100 0 low quantities of high quantities of phytoplankton phytoplankton rocky shore Fig. 1.3 (ii) Summarise the results of the investigation shown in Fig. 1.3. … … … … [2] (iii) The scientists concluded that there was a strong probability that the presence of dogwhelks affects the settlement of barnacles onto rocks. Discuss the extent to which the error bars for standard deviation shown in Fig. 1.3 support the scientists’ conclusion. … … … … [2] (iv) Suggest explanations for the effect of dogwhelks and quantities of phytoplankton on the settling of the barnacles. … … … … … … [3] (c) The acorn barnacle has spread all around the world on ships and is now considered to be an invasive species. (i) Explain why invasive species are a risk to ecosystems. … … … … … … [3] (ii) It has been suggested that introducing dogwhelks into new areas colonised by acorn barnacles could be a method of control. Suggest a possible negative consequence of introducing dogwhelks into areas with acorn barnacles. … … [1] [Total: 15]
15 marks
Mark scheme: Question Answer Marks 1(a) any 2 of: 2 allows dispersal to wider area / other areas / moves to different locations / AW ; to reduce competition / larvae have different niches from adults / AW ; allows (larvae to) feed on plankton / AW ; 1(b)(i) 533 (to 3 sig figs) ;; 2 1(b)(ii) more barnacles are found on the shores where there are more phytoplankton / ORA ; 2 more barnacles where there are no dogwhelks / ORA ; 1(b)(iii) any 2 of: 2 supported because no overlap (with and without dogwhelks) on shore with low quantities of phytoplankton / AW ; less support as there is an overlap (with and without dogwhelks) with larger quantities of phytoplankton / AW ; other factors may be affecting result / correlation not causal ; 1(b)(iv) any 3 of: 3 barnacles consume phytoplankton / more food for barnacles (if more phytoplankton) / ORA / AW ; so more survival of larvae ; dogwhelks reduces, attachment / settling, of barnacle larvae ; due to presence of, chemicals / scent, from dogwhelks / AW ; less reproduction of barnacles (to reduce population) (when dogwhelks present / less phytoplankton) / AW ; 1(c)(i) any 3 of: 3 lack predators so increase in population / AW ; overconsume prey / AW ; out compete native species / AW ; AVP ; 1(c)(ii) may become an invasive species itself / may have no predator / consume other native species / AW ; 1
This question in 9693/42 Oct/Nov 2024
Q40 · Agriculture poses a threat to coral reefs in many parts of the world due to the run-off… 9693/42 Oct/Nov 2024
3 Agriculture poses a threat to coral reefs in many parts of the world due to the run-off of fertilisers and herbicides into the sea. (a) Explain how fertiliser run-off can pose a threat to coral reefs. … … … … … … [3] (b) Herbicides are chemicals that are used to kill weeds on farmland. Scientists investigated the effect of herbicides on the production of ATP, the production of reduced NADP and the rate of carbon fixation by dinoflagellates. Suspensions of chloroplasts taken from dinoflagellates were placed into a test-tube in bright light. The concentrations of ATP, reduced NADP and glucose were measured at time 0. Herbicide was added to the test-tube and the concentrations of ATP, reduced NADP and glucose were measured after 10 minutes, 20 minutes and 30 minutes. The results are shown in Table 3.1. Table 3.1 time / min concentration of ATP concentration of concentration of / arbitrary units reduced NADP glucose / arbitrary units / arbitrary units 0 25 21 15 10 15 15 15 20 10 5 10 30 10 1 5 (i) Compare the change in concentration of ATP with the change in the concentration of reduced NADP over the 30-minute period. … … … … [2] (ii) The herbicide reduces the concentration of chlorophyll in the chloroplasts of dinoflagellates. Explain the effect of adding herbicide on the changes in concentration of ATP and reduced NADP shown in Table 3.1. … … … … … … [3] (iii) Explain the effect of adding herbicide on the change in concentration of glucose shown in Table 3.1. … … … … … … [3] (c) Marine diatoms are planktonic producers. Fig. 3.1 shows a photograph of some marine diatoms. Fig. 3.1 Make a large drawing of the part of the diatom shown inside the box in Fig. 3.1. Do not label your diagram. [4] [Total: 15]
15 marks
Mark scheme: 3(a) any 3 of: 3 1 release of nitrogen / phosphorus ; 2 (increased) algal growth / algal blooms / eutrophication / AW ; 3 (covering coral so) reducing light intensity / AW ; 4 reducing photosynthesis (of coral) / reducing (primary) productivity / AW ; 5 (increased) decomposition ; 6 loss of oxygen ; 7 AVP ; 3(b)(i) any 2 of: 2 both decrease ; ATP levels off / reduced NADP continues to fall / AW ; greater fall in NADP than ATP / ORA / AW ; 3(b)(ii) any 3 of: 3 less light-dependent stage ; less light trapped by chlorophyll / less photoactivation of chlorophyll / AW ; less transfer of energy from, light / chlorophyll, to ATP / reduced NADP ; some ATP continues to be produced via respiration ; AVP ; 3(b)(iii) any 3 of: 3 glucose concentration falls / AW ; light-independent stage does not occur ; due to loss of ATP / reduced NADP ; less fixation of carbon / AW ; glucose is used in respiration ; glucose is converted to starch / organic molecules / other named substance ; 3(c) lines are thin, clear, unbroken and no shading ; 4 at least one third of space used ; correct proportions of cell width, length and chloroplasts ; correct detail ; correct number of chloroplasts (minimum of 8) + double line for cell wall ;
This question in 9693/42 Oct/Nov 2024
Q41 · Some barnacles and a dogwhelk on a rock 9693/43 Oct/Nov 2024
1 Fig. 1.1 shows some barnacles and a dogwhelk on a rock. Fig. 1.1 Adult barnacles are sessile and are often found attached to rocks on rocky shores. Barnacles have a complex life cycle with planktonic larvae. (a) Explain why a complex life cycle is an advantage for sessile organisms. … … … … [2] (b) The dogwhelk feeds on barnacles on rocky shores. Scientists investigated whether the settlement of barnacles on a rocky shore was affected by: • the presence of dogwhelks • the quantity of phytoplankton in the sea water next to the shore. The scientists placed 0.25 m2 plastic tiles onto four rocky shores: • one shore with a high quantity of phytoplankton in the sea and with dogwhelks present • one shore with a high quantity of phytoplankton in the sea and with no dogwhelks present • one shore with a low quantity of phytoplankton in the sea and with dogwhelks present • one shore with a low quantity of phytoplankton in the sea and with no dogwhelks present. All the tiles had a central area which dogwhelks could not access. Fig. 1.2 shows one of the tiles used. central area covered with mesh to stop dogwhelks getting in plastic tile Fig. 1.2 The plastic tiles were examined after two months. The population densities of the barnacles growing in the central area which dogwhelks could not access were calculated. (i) The central area of one plastic tile had 12 barnacles settled in an area of 0.0225 m2. Calculate the population density of barnacles for this plastic tile as the number of barnacles per m2. Give your answer to three significant figures. … per m2 [2] Fig. 1.3 shows the population density of barnacles that had settled on the plastic tiles on all four rocky shores. Key dogwhelks present dogwhelks not present 800 700 600 500 number of barnacles 400 per square metre 300 200 100 0 low quantities of high quantities of phytoplankton phytoplankton rocky shore Fig. 1.3 (ii) Summarise the results of the investigation shown in Fig. 1.3. … … … … [2] (iii) The scientists concluded that there was a strong probability that the presence of dogwhelks affects the settlement of barnacles onto rocks. Discuss the extent to which the error bars for standard deviation shown in Fig. 1.3 support the scientists’ conclusion. … … … … [2] (iv) Suggest explanations for the effect of dogwhelks and quantities of phytoplankton on the settling of the barnacles. … … … … … … [3] (c) The acorn barnacle has spread all around the world on ships and is now considered to be an invasive species. (i) Explain why invasive species are a risk to ecosystems. … … … … … … [3] (ii) It has been suggested that introducing dogwhelks into new areas colonised by acorn barnacles could be a method of control. Suggest a possible negative consequence of introducing dogwhelks into areas with acorn barnacles. … … [1] [Total: 15]
15 marks
Mark scheme: Question Answer Marks 1(a) any 2 of: 2 allows dispersal to wider area / other areas / moves to different locations / AW ; to reduce competition / larvae have different niches from adults / AW ; allows (larvae to) feed on plankton / AW ; 1(b)(i) 533 (to 3 sig figs) ;; 2 1(b)(ii) more barnacles are found on the shores where there are more phytoplankton / ORA ; 2 more barnacles where there are no dogwhelks / ORA ; 1(b)(iii) any 2 of: 2 supported because no overlap (with and without dogwhelks) on shore with low quantities of phytoplankton / AW ; less support as there is an overlap (with and without dogwhelks) with larger quantities of phytoplankton / AW ; other factors may be affecting result / correlation not causal ; 1(b)(iv) any 3 of: 3 barnacles consume phytoplankton / more food for barnacles (if more phytoplankton) / ORA / AW ; so more survival of larvae ; dogwhelks reduces, attachment / settling, of barnacle larvae ; due to presence of, chemicals / scent, from dogwhelks / AW ; less reproduction of barnacles (to reduce population) (when dogwhelks present / less phytoplankton) / AW ; 1(c)(i) any 3 of: 3 lack predators so increase in population / AW ; overconsume prey / AW ; out compete native species / AW ; AVP ; 1(c)(ii) may become an invasive species itself / may have no predator / consume other native species / AW ; 1
This question in 9693/43 Oct/Nov 2024
Q42 · Agriculture poses a threat to coral reefs in many parts of the world due to the run-off… 9693/43 Oct/Nov 2024
3 Agriculture poses a threat to coral reefs in many parts of the world due to the run-off of fertilisers and herbicides into the sea. (a) Explain how fertiliser run-off can pose a threat to coral reefs. … … … … … … [3] (b) Herbicides are chemicals that are used to kill weeds on farmland. Scientists investigated the effect of herbicides on the production of ATP, the production of reduced NADP and the rate of carbon fixation by dinoflagellates. Suspensions of chloroplasts taken from dinoflagellates were placed into a test-tube in bright light. The concentrations of ATP, reduced NADP and glucose were measured at time 0. Herbicide was added to the test-tube and the concentrations of ATP, reduced NADP and glucose were measured after 10 minutes, 20 minutes and 30 minutes. The results are shown in Table 3.1. Table 3.1 time / min concentration of ATP concentration of concentration of / arbitrary units reduced NADP glucose / arbitrary units / arbitrary units 0 25 21 15 10 15 15 15 20 10 5 10 30 10 1 5 (i) Compare the change in concentration of ATP with the change in the concentration of reduced NADP over the 30-minute period. … … … … [2] (ii) The herbicide reduces the concentration of chlorophyll in the chloroplasts of dinoflagellates. Explain the effect of adding herbicide on the changes in concentration of ATP and reduced NADP shown in Table 3.1. … … … … … … [3] (iii) Explain the effect of adding herbicide on the change in concentration of glucose shown in Table 3.1. … … … … … … [3] (c) Marine diatoms are planktonic producers. Fig. 3.1 shows a photograph of some marine diatoms. Fig. 3.1 Make a large drawing of the part of the diatom shown inside the box in Fig. 3.1. Do not label your diagram. [4] [Total: 15]
15 marks
Mark scheme: 3(a) any 3 of: 3 1 release of nitrogen / phosphorus ; 2 (increased) algal growth / algal blooms / eutrophication / AW ; 3 (covering coral so) reducing light intensity / AW ; 4 reducing photosynthesis (of coral) / reducing (primary) productivity / AW ; 5 (increased) decomposition ; 6 loss of oxygen ; 7 AVP ; 3(b)(i) any 2 of: 2 both decrease ; ATP levels off / reduced NADP continues to fall / AW ; greater fall in NADP than ATP / ORA / AW ; 3(b)(ii) any 3 of: 3 less light-dependent stage ; less light trapped by chlorophyll / less photoactivation of chlorophyll / AW ; less transfer of energy from, light / chlorophyll, to ATP / reduced NADP ; some ATP continues to be produced via respiration ; AVP ; 3(b)(iii) any 3 of: 3 glucose concentration falls / AW ; light-independent stage does not occur ; due to loss of ATP / reduced NADP ; less fixation of carbon / AW ; glucose is used in respiration ; glucose is converted to starch / organic molecules / other named substance ; 3(c) lines are thin, clear, unbroken and no shading ; 4 at least one third of space used ; correct proportions of cell width, length and chloroplasts ; correct detail ; correct number of chloroplasts (minimum of 8) + double line for cell wall ;
This question in 9693/43 Oct/Nov 2024
Q43 · Oysters are shelled molluscs that have a complex life cycle 9693/41 May/June 2025
3 Oysters are shelled molluscs that have a complex life cycle. The adults are sessile organisms that anchor to a substrate. Fig. 3.1 shows some adult oysters. Fig. 3.1 (a) Outline the importance of having a complex life cycle for organisms such as oysters. … … … … … … [3] (b) Scientists investigated the effects of temperature and pH on the survival of oyster larvae. Oyster larvae were placed into tanks of water at different temperatures and pHs. The percentages of larvae surviving were calculated after two days and then again after 15 days. Fig. 3.2 and Fig. 3.3 show the results. 100 Key 90 day 2 day 15 80 70 60 percentage of 50 larvae surviving 40 30 20 10 0 20 25 27 30 35 temperature / °C Fig. 3.2 100 Key 90 day 2 day 15 80 70 60 percentage of 50 larvae surviving 40 30 20 10 0 6.5 7.0 7.5 8.0 8.2 8.5 pH Fig. 3.3 (i) The scientists placed 500 larvae in each condition. Calculate the number of larvae that did not survive from day 2 to day 15 when placed at a temperature of 30 °C. … [2] (ii) Use Fig. 3.2 and Fig. 3.3 to state the optimum temperature and optimum pH for the survival of oyster larvae. optimum temperature … °C optimum pH … [1] (c) Fishers in India reported declining harvests of adult oysters from an area of coastal water after 2011. (i) Table 3.1 shows the temperature and pH of the water during 2009 in this area. Table 3.1 month temperature / °C pH February 25 8.0 April 27 7.9 June 34 8.2 August 30 7.0 October 32 6.5 December 28 7.0 Use Table 3.1 to plot a line graph to show the temperature and the pH from February to December. [5] (ii) Around the coasts of India, oysters spawn throughout the year but have two peak periods of breeding, in April and August. Discuss the reasons for the reduction in the number of oysters that the fishers harvested after 2011. Use information in Table 3.1, Fig. 3.2 and Fig. 3.3 to support your answer. … … … … … … … … [4] (d) Explain why the use of fossil fuels places future oyster populations at risk. … … … … … … [3] [Total: 18]
18 marks
Mark scheme: 3(a) any 3 from: 3 1 larvae can move to other areas / larvae allow distribution to other areas / AW ; 2 reduced competition / AW ; 3 (reduced competition for) food / nutrients / AW ; 4 idea that larvae and adults occupy different niches / AW ; 5 increased genetic diversity (if oysters spread to other areas) / AW ; 6 reduces spread of disease (as population density is lower) ; 3(b)(i) 180 = 2 marks 2 36 (%) = 1 mark OR 320 survived = 1 mark 3(b)(ii) (optimum temperature) = 27 (°C) 1 optimum pH = 8(.0) ; 3(c)(i) 1. linear y axes for both temperature and pH, labelled with units, and horizontal axis as month ; 5 2. all three scales enable plots to cover at least half grid ; 3. plots correct +/- ½ square for temperature ; 4. plots correct +/- ½ square for pH ; 5. points joined with straight lines and key ; 3(c)(ii) any 4 from: 4 1 in April, conditions enable survival / there are optimal conditions / oysters can breed / conditions are ideal for breeding / AW ; 2 August has a temperature of 30 oC and pH of 7(.0) / April has a temperature of 27 oC and pH of 7.9 / AW ; 3 in August, conditions reduce larvae settling / kill larvae / few larvae survive / will not settle in August / too acidic for survival / AW ; 4 there is only one successful breeding season (per year) / AW ; 5 idea that few oyster larvae become adults / it takes time to produce adults (so effects are only seen in 2011) / AW ; 6 few other months have ideal conditions for larvae / AW ; 7 overfishing / pollution / AW, may be causing the fall ; 3(d) any 3 from: 3 1 release of carbon dioxide / AW ; 2 causes (enhanced) greenhouse effect / increased temperature / global warming / AW ; 3 acidification of water / AW ; 4 (acid) reduces oyster shell formation / erodes shells / dissolves shells / AW ; 5 larvae do not survive / larvae cannot settle / fewer adult oysters to breed (in future) / AW ;
This question in 9693/41 May/June 2025
Q44 · A photograph of Palau which is a nation located in the Pacific Ocean 9693/41 May/June 2025
5 Fig. 5.1 shows a photograph of Palau which is a nation located in the Pacific Ocean. Palau consists of a series of islands surrounded by a range of coral reefs. Fig. 5.1 Reef fish are an important part of the diet for local people in Palau. In 2017, fishing restrictions were implemented in Palau to make fishing sustainable. In some areas, all fishing was banned. (a) State two other important methods of restriction that could be used to ensure that the Palau fishery is sustainable. 1 … 2 … [2] (b) State one negative sociological impact on the people in Palau caused by restrictions on fishing. … … [1] (c) Scientists investigated the effect of the restrictions by sampling commercial species of reef fish in 2017 and 2019. In each year, fish were sampled at 150 sites around Palau by divers using cameras. The results are shown in Fig. 5.2 and Fig. 5.3. Fig. 5.2 shows the mean biomass of reef fish in 2017 and 2019. Fig. 5.3 shows the mean biomass of fish that are herbivores, fish that are secondary consumers, and high trophic level fish that consume other fish species, in 2017 and 2019. 30 25 20 mean fish 15 biomass / g m–2 10 5 0 2017 2019 year Fig. 5.2 12 Key 10 herbivore secondary consumer 8 high trophic level fish mean fish 6biomass / g m–2 4 2 0 2017 2019 year Fig. 5.3 Evaluate the effects of the fishing restrictions on the sustainability of the Palau fishery. Use Fig. 5.2 and Fig. 5.3 to support your answer. … … … … … … … … [4] [Total: 7]
7 marks
Mark scheme: 5(a) any 2 from: 2 1 method / net (volume) sizes / AW ; 2 season / time of year / breeding season / AW ; 3 location / area / breeding grounds / MPAs / AW ; 4 fishing intensity / fishing effort / boat days / boat sizes / AW ; 5 setting quotas / size of catch / / AW ; 6 fish size / set minimum sizes (that can be kept) / mesh size on net / age of fish / AW ; 7 licensing / AW ; 5(b) any 1 from: 1 • lack of food / starvation / malnutrition / lack of protein / AW ; • poverty / lack of income / AW ; • unemployment / lack of jobs / lack of work / AW ; • loss of services (in the area) / loss of tourism / AW ; • unable to care for families / AW ; • loss of culture / traditions / AW ; • conflict with government / authorities / AW ; • increased crime / more at risk of prosecutions / risk of fines / AW ; • AVP ; 5(c) any 4 from: 4 (at least 1 from) supported because 1 increase in (overall) biomass / increase in (biomass of), herbivores / secondary consumers / AW ; 2 significant increase in herbivores as error bars do not overlap / AW ; 3 more food for, secondary consumers / carnivores / higher trophic levels (due to more herbivores) / more energy for, secondary consumers / carnivores / higher trophic levels / AW ; 4 reliable / valid, as large sample size used / many areas used / AW ; (at least 1 from) not supported because 5 high trophic level fish is only a small increase / AW ; 6 error bars for high trophic level fish / secondary consumers / (overall) biomass, overlap so no significant difference / AW ; 7 large error bars suggests, wide variation / range (in biomass) / AW ; 8 only a short period of time (so not reliable) / no information about time of year / AW ; 9 no reference to, types of species / numbers of individual species / populations / AW ;
This question in 9693/41 May/June 2025
Q45 · A photograph of a ship’s rudder and propeller covered in barnacles 9693/41 May/June 2025
6 Fig. 6.1 shows a photograph of a ship’s rudder and propeller covered in barnacles. Fig. 6.1 Antifouling paints are often used to prevent barnacle larvae settling on boats. (a) Outline why many antifouling paints that contained heavy metals are now banned. … … … … [2] (b) Bromosphaerol is a natural substance produced by red algae that may work as an antifouling agent. Plan a laboratory investigation that you could do to investigate the effect of increasing concentration of bromosphaerol on the growth of barnacles on a substrate. You would be provided with a 1 g dm–3 stock solution of bromosphaerol solution. Bromosphaerol may be an irritant. Your plan should: • include a clear statement of the hypothesis • identify the independent, dependent, and standardised variables • include full details of the method so that another person can follow it • describe how you would analyse your results • be safe and ethical. … … … … … … … … … … … … … … … … … … … … … … … … [11] [Total: 13]
13 marks
Mark scheme: 6(a) any 2 from: 2 1 toxic / AW ; 2 transferred through food chains / concentration increases along food chains / AW ; 3 bioaccumulation occurs / do not break down / are not excreted / AW ; 4 AVP ; 6(b) any 1 from: 11 hypothesis (h) • increasing concentration of bromosphaerol reduces growth of barnacles / AW any 10 from: independent variable (i): • independent variable / IV, is concentration of bromosphaerol ; • make up at least five different concentrations (must have units or percentage at least once) ; dependent variable (d): • dependent variable / DV, is number of barnacles / mass of barnacles / area covered / AW ; • method of, measuring area of barnacles / measuring mass of barnacles / counting barnacles / AW ; 6(b) standardised variables (c): (MAX 3) • same salinity / salt concentration / same or stated ppt ; • same pH ; • same temperature / suitable stated temperature ; • same material for substrate / same sized substrate / same type of substrate / AW ; • same volume of solution / water / AW ; • same species of barnacle / number of barnacle (larvae) added / AW ; • same food / mass of food / AW ; • same oxygen (concentration) / same carbon dioxide (concentration) ; • same light intensity / colour / wavelength / distance of lamp / AW ; • same length of time / stated time period / AW ; method details (m): (MAX 2) • use of serial / proportional dilutions ; • use of pipettes / syringe / measuring cylinder (to measure volume) / thermometer to measure temperature / AW ; • correct method for maintain temperature, e.g. water bath / heat lamp / aquarium heater / AW ; • use of pH buffer (to maintain pH) ; • use of oxygenation / AW ; 6(b) safety and ethics (e) • suitable safety measure and reason, e.g. gloves / eye protection / AW, as bromosphaerol is an irritant / harmful / AW ; • suitable ethical measure, e.g. avoid extreme temperature or pH or salinity / dispose of solutions carefully / do not tip solutions down sink / into environment / AW ; analysis (a): (MAX 3) • suitable graph described ; • replicates / repeat at least twice and calculate, means / medians / standard deviations ; • use of standard error to compare means / use of Spearman’s rank to see if correlation (between concentration and barnacle number) / AW ; • suitable example of table ;
This question in 9693/41 May/June 2025
Q46 · Carbon dioxide produced by the combustion of fossil fuels may lead to ocean acidification 9693/42 May/June 2025
3 Carbon dioxide produced by the combustion of fossil fuels may lead to ocean acidification. (a) Describe how carbon dioxide reacts with water to increase the acidity. … … … … [2] (b) Fig. 3.1 shows a photograph of a free-swimming planktonic mollusc, Limacina helicina. This shelled species of mollusc is an important part of many Arctic food chains. Fig. 3.1 Scientists investigated the effect of changing pH on the mass of calcium carbonate deposited into the shells of Limacina helicina during larval development. Three larvae were incubated in each of two tanks of sea water, one at pH 8.1 and the other at pH 7.8. The mass of calcium carbonate deposited into the shells was measured every two hours for six hours. Fig. 3.2 shows the results. 3.0 line of best fit for pH 8.1 2.0 mass of calcium line of best fit for pH 7.8carbonate deposited in shell / μmol g–1 1.0 Key reading for individual animals at pH 8.1 reading for individual 0 animals at pH 7.8 0 1 2 3 4 5 6 7 time / hr Fig. 3.2 (i) Use the line of best fit in Fig. 3.2 to calculate the mean rate of calcium deposition for the mollusc larvae when placed at pH 7.8. State the unit. Show your working. … [3] (ii) A pH of 8.1 is the normal pH of water from the Arctic Ocean where Limacina helicina is found. Discuss the possible impact of ocean acidification on Arctic food webs. Use Fig. 3.2 to support your answer. … … … … … … … … [4] (c) Renewable energy installations such as wind turbines may help to reduce dependency on fossil fuels. Some scientists are concerned that the noise generated by the building of offshore wind turbines may affect the behaviour of marine mammals such as porpoises. An offshore wind turbine area was built in an area of the North Sea during 2006. Scientists recorded the number of days over six-month periods that porpoises were seen in the area: • before construction, in 2005 • during construction, in 2006 • after construction had finished, in 2007. To see if there was a significant difference in porpoise numbers during these three periods, a chi-squared ( χ 2) test was performed. Table 3.1 shows the chi-squared test results. Table 3.1 year number of expected (O – E) (O – E)2 (O – E)2 / E days that number of porpoises days that were detected porpoises (O) were detected (E) 2005 56 49 7 49 1.0 (before construction) 2006 54 49 5 25 0.5 (during construction) 2007 36 49 (after construction) (i) Complete Table 3.1. [1] (ii) Use Table 3.1 to calculate the value of chi-squared ( χ 2). Use the formula: (O – E)2 χ 2 = Σ E where, χ 2 = chi-squared value O = observed values E = expected values Σ = sum of … [1] (iii) The scientists made the null hypothesis: ‘There is no difference in the number of days that the area was visited by porpoises before, during or after construction of the offshore wind turbines.’ Table 3.2 shows the critical values of chi-squared. Table 3.2 probability degrees of freedom 0.50 0.10 0.05 0.01 1 0.455 2.706 3.841 6.635 2 1.386 4.605 5.991 9.210 3 2.366 6.251 7.815 11.345 4 3.357 7.779 9.488 13.277 Use your answer to 3(c)(ii) and Table 3.2 to assess the impact of the wind turbines on the porpoises. … … … … … … … … [4] (d) The use of renewable energy could reduce the risk of ocean acidification. State two other benefits of increasing the use of renewable energy installations. 1 … … 2 … … [2] [Total: 17]
17 marks
Mark scheme: 3(a) any 2 of: 2 1 forms carbonic acid / H2CO3 / AW ; 2 (dissociates) into H+ and HCO3– / results in high concentration of H+ / AW ; 3(b)(i) 0.22 to 0.25 ;; 3 mol g-1 hr-1 ; One mark for correct values of pH change and time 3(b)(ii) any 4 of: 4 1 rate of calcium carbonate deposition is lower at pH 7.8 / AW ; 2 as less carbonate (available) / CO32– AW ; 3 so weaker shells / AW ; 4 lower survival / populations fall / easily predated / AW ; 5 lower primary productivity (due to low pH) / less photosynthesis by producers / AW ; 6 less food / biomass / energy to pass along food chain (for higher trophic levels) / AW ; 7 algae populations could increase if fewer snails to consume them / AW ; 8 range of points on graph overlap / large range of masses / points are far from lines of best fit / weak correlation / AW ; 9 sample size is low ; 3(c)(i) 1 year number expected (O–E) (O–E)2 (O–E)2 / E of days number that of days porpoises that were porpoises detected were (O) detected (E) 2005 (before 56 49 7 49 1 construction) 2006 (during 54 49 5 25 0.5 construction) 2007 (after 36 49 –13 169 3.4(5) ; construction) 3(c)(ii) 4.9(5) ; 1 3(c)(iii) any 4 of: 4 1 null hypothesis is, not rejected / accepted, / porpoises are not harmed by wind turbine construction ; 2 calculated value is lower than critical value / AW ; 3 identified critical value as 5.991 ; 4 greater than 5% probability that the difference is due to chance ; 5 no significant difference / porpoise movement is not significantly affected ; 3(d) any 2 of: 2 1 (reduced dependency on fossil fuels so) reduced greenhouse effect / less climate change / less global warming / less risk of sea level rises / AW ; 2 will not run out / renewable / sustainable / AW ; 3 low risk of acid rain ; 4 low risk of oil spills ; 5 no habitat damage from (oil) drilling / AW ;
This question in 9693/42 May/June 2025
Q47 · Turgor pressure is the force exerted by the contents of the cytoplasm of a plant cell… 9693/42 May/June 2025
4 Turgor pressure is the force exerted by the contents of the cytoplasm of a plant cell when the cell membrane presses outwards against the cell wall. Turgor pressure is measured in megapascals (MPa). A student investigated the effect of different concentrations of sucrose on mass and turgor pressure in mangrove roots. Equal-sized pieces of mangrove root were placed into five different sucrose solutions and also placed into pure water. After six hours, the student calculated the percentage change in mass of the roots and the turgor pressure in the root cells. The results are shown in Table 4.1. Table 4.1 sucrose concentration percentage change in turgor pressure / mol dm–3 mass / MPa 0.00 +25 0.42 0.25 +15 0.28 0.50 +10 0.14 0.75 –5 0.00 1.00 –10 0.00 1.25 –25 0.00 (a) (i) Draw a line graph to show the percentage change in mass and the turgor pressure when the roots were placed in the different concentrations of sucrose. Join your points with ruled straight lines. [5] (ii) Explain the effect of increasing sucrose concentration on the percentage change in mass of the roots. … … … … … … [3] (iii) Explain the effect of increasing sucrose concentration on the turgor pressure. … … … … [2] (b) Reverse osmosis is a method that can be used to produce fresh water from sea water. Fig. 4.1 is a diagram to show how reverse osmosis works. pressure from pump A B fresh water dissolved salts in sea water water flow selectively permeable membrane Fig. 4.1 (i) A pump forces sea water under pressure into chamber A. Fresh water is produced in chamber B. Explain why pressure is needed to produce the fresh water in chamber B. … … … … [2] (ii) Chamber A contains a very concentrated solution of salts after the reverse osmosis process has finished. Explain why this solution in chamber A should not be returned to the sea. … … … … … … [3] [Total: 15]
15 marks
Mark scheme: 4(a)(i) 1 two linear y-axes and linear x-axis labelled with units ; 5 2 both plotted lines taken up at least three large squares ; 3 correct plots for percentage change in mass (+/– ½ square) ; 4 correct plots for turgor pressure (+/– ½ square) ; 5 plots joined with straight lines and lines have a key or are labelled ; 4(a)(ii) any 3 of: 3 1 at low concentrations / below 0.5, mass increases / water enters cells, / AW ; 2 at high concentrations / above 0.75 / value from graph, decrease in mass / water leaves cells ; 3 (water moves in / out) by osmosis ; 4 (water moves) from a higher water potential to a lower water potential ; 5 solute concentration of cells is equivalent to value from graph where line intersects x-axis ; 4(a)(iii) any 2 of: 2 1 turgor pressure decreases up to concentration of 0.75 and then levels off (at zero) / AW ; 2 because as concentration increases, water content of cells is less / AW ; 3 below 0.75, membrane presses / touches cell wall / AW ; 4 over 0.75, cell membrane peels away from cell wall / cells has become plasmolysed / AW ; 4(b)(i) any 2 of: 2 1 water would (naturally) move into chamber A / from chamber B / from freshwater to sea water / AW ; 2 as the water potential of B is higher than A / water would down the water potential gradient / water is being forced against the water potential gradient / AW ; 3 so pressure needs to be greater than osmotic force / pressure / AW ; 4 salts cannot pass through the membrane / only water can pass through the membrane / AW ; 4(b)(ii) any 3 of: 3 1 salinity of the sea increases / water potential decreases ; 2 affects osmoconformer species / AW ; 3 water would be lost (from organisms) / cause dehydration / AW ; 4 alters density of water / salinity gradients / haloclines / AW ; 5 (high salinity) would reduce oxygen content of water / AW ; 6 causing organisms to suffocate / reduces respiration / AW ; 7 (the salt solution) may also contain high concentrations of toxins / AW ; 8 AVP ;
This question in 9693/42 May/June 2025
Q48 · Carbon dioxide produced by the combustion of fossil fuels may lead to ocean acidification 9693/43 May/June 2025
3 Carbon dioxide produced by the combustion of fossil fuels may lead to ocean acidification. (a) Describe how carbon dioxide reacts with water to increase the acidity. … … … … [2] (b) Fig. 3.1 shows a photograph of a free-swimming planktonic mollusc, Limacina helicina. This shelled species of mollusc is an important part of many Arctic food chains. Fig. 3.1 Scientists investigated the effect of changing pH on the mass of calcium carbonate deposited into the shells of Limacina helicina during larval development. Three larvae were incubated in each of two tanks of sea water, one at pH 8.1 and the other at pH 7.8. The mass of calcium carbonate deposited into the shells was measured every two hours for six hours. Fig. 3.2 shows the results. 3.0 line of best fit for pH 8.1 2.0 mass of calcium line of best fit for pH 7.8carbonate deposited in shell / μmol g–1 1.0 Key reading for individual animals at pH 8.1 reading for individual 0 animals at pH 7.8 0 1 2 3 4 5 6 7 time / hr Fig. 3.2 (i) Use the line of best fit in Fig. 3.2 to calculate the mean rate of calcium deposition for the mollusc larvae when placed at pH 7.8. State the unit. Show your working. … [3] (ii) A pH of 8.1 is the normal pH of water from the Arctic Ocean where Limacina helicina is found. Discuss the possible impact of ocean acidification on Arctic food webs. Use Fig. 3.2 to support your answer. … … … … … … … … [4] (c) Renewable energy installations such as wind turbines may help to reduce dependency on fossil fuels. Some scientists are concerned that the noise generated by the building of offshore wind turbines may affect the behaviour of marine mammals such as porpoises. An offshore wind turbine area was built in an area of the North Sea during 2006. Scientists recorded the number of days over six-month periods that porpoises were seen in the area: • before construction, in 2005 • during construction, in 2006 • after construction had finished, in 2007. To see if there was a significant difference in porpoise numbers during these three periods, a chi-squared ( χ 2) test was performed. Table 3.1 shows the chi-squared test results. Table 3.1 year number of expected (O – E) (O – E)2 (O – E)2 / E days that number of porpoises days that were detected porpoises (O) were detected (E) 2005 56 49 7 49 1.0 (before construction) 2006 54 49 5 25 0.5 (during construction) 2007 36 49 (after construction) (i) Complete Table 3.1. [1] (ii) Use Table 3.1 to calculate the value of chi-squared ( χ 2). Use the formula: (O – E)2 χ 2 = Σ E where, χ 2 = chi-squared value O = observed values E = expected values Σ = sum of … [1] (iii) The scientists made the null hypothesis: ‘There is no difference in the number of days that the area was visited by porpoises before, during or after construction of the offshore wind turbines.’ Table 3.2 shows the critical values of chi-squared. Table 3.2 probability degrees of freedom 0.50 0.10 0.05 0.01 1 0.455 2.706 3.841 6.635 2 1.386 4.605 5.991 9.210 3 2.366 6.251 7.815 11.345 4 3.357 7.779 9.488 13.277 Use your answer to 3(c)(ii) and Table 3.2 to assess the impact of the wind turbines on the porpoises. … … … … … … … … [4] (d) The use of renewable energy could reduce the risk of ocean acidification. State two other benefits of increasing the use of renewable energy installations. 1 … … 2 … … [2] [Total: 17]
17 marks
Mark scheme: 3(a) any 2 of: 2 1 forms carbonic acid / H2CO3 / AW ; 2 (dissociates) into H+ and HCO3– / results in high concentration of H+ / AW ; 3(b)(i) 0.22 to 0.25 ;; 3 mol g-1 hr-1 ; One mark for correct values of pH change and time 3(b)(ii) any 4 of: 4 1 rate of calcium carbonate deposition is lower at pH 7.8 / AW ; 2 as less carbonate (available) / CO32– AW ; 3 so weaker shells / AW ; 4 lower survival / populations fall / easily predated / AW ; 5 lower primary productivity (due to low pH) / less photosynthesis by producers / AW ; 6 less food / biomass / energy to pass along food chain (for higher trophic levels) / AW ; 7 algae populations could increase if fewer snails to consume them / AW ; 8 range of points on graph overlap / large range of masses / points are far from lines of best fit / weak correlation / AW ; 9 sample size is low ; 3(c)(i) 1 year number expected (O–E) (O–E)2 (O–E)2 / E of days number that of days porpoises that were porpoises detected were (O) detected (E) 2005 (before 56 49 7 49 1 construction) 2006 (during 54 49 5 25 0.5 construction) 2007 (after 36 49 –13 169 3.4(5) ; construction) 3(c)(ii) 4.9(5) ; 1 3(c)(iii) any 4 of: 4 1 null hypothesis is, not rejected / accepted, / porpoises are not harmed by wind turbine construction ; 2 calculated value is lower than critical value / AW ; 3 identified critical value as 5.991 ; 4 greater than 5% probability that the difference is due to chance ; 5 no significant difference / porpoise movement is not significantly affected ; 3(d) any 2 of: 2 1 (reduced dependency on fossil fuels so) reduced greenhouse effect / less climate change / less global warming / less risk of sea level rises / AW ; 2 will not run out / renewable / sustainable / AW ; 3 low risk of acid rain ; 4 low risk of oil spills ; 5 no habitat damage from (oil) drilling / AW ;
This question in 9693/43 May/June 2025
Q49 · Turgor pressure is the force exerted by the contents of the cytoplasm of a plant cell… 9693/43 May/June 2025
4 Turgor pressure is the force exerted by the contents of the cytoplasm of a plant cell when the cell membrane presses outwards against the cell wall. Turgor pressure is measured in megapascals (MPa). A student investigated the effect of different concentrations of sucrose on mass and turgor pressure in mangrove roots. Equal-sized pieces of mangrove root were placed into five different sucrose solutions and also placed into pure water. After six hours, the student calculated the percentage change in mass of the roots and the turgor pressure in the root cells. The results are shown in Table 4.1. Table 4.1 sucrose concentration percentage change in turgor pressure / mol dm–3 mass / MPa 0.00 +25 0.42 0.25 +15 0.28 0.50 +10 0.14 0.75 –5 0.00 1.00 –10 0.00 1.25 –25 0.00 (a) (i) Draw a line graph to show the percentage change in mass and the turgor pressure when the roots were placed in the different concentrations of sucrose. Join your points with ruled straight lines. [5] (ii) Explain the effect of increasing sucrose concentration on the percentage change in mass of the roots. … … … … … … [3] (iii) Explain the effect of increasing sucrose concentration on the turgor pressure. … … … … [2] (b) Reverse osmosis is a method that can be used to produce fresh water from sea water. Fig. 4.1 is a diagram to show how reverse osmosis works. pressure from pump A B fresh water dissolved salts in sea water water flow selectively permeable membrane Fig. 4.1 (i) A pump forces sea water under pressure into chamber A. Fresh water is produced in chamber B. Explain why pressure is needed to produce the fresh water in chamber B. … … … … [2] (ii) Chamber A contains a very concentrated solution of salts after the reverse osmosis process has finished. Explain why this solution in chamber A should not be returned to the sea. … … … … … … [3] [Total: 15]
15 marks
Mark scheme: 4(a)(i) 1 two linear y-axes and linear x-axis labelled with units ; 5 2 both plotted lines taken up at least three large squares ; 3 correct plots for percentage change in mass (+/– ½ square) ; 4 correct plots for turgor pressure (+/– ½ square) ; 5 plots joined with straight lines and lines have a key or are labelled ; 4(a)(ii) any 3 of: 3 1 at low concentrations / below 0.5, mass increases / water enters cells, / AW ; 2 at high concentrations / above 0.75 / value from graph, decrease in mass / water leaves cells ; 3 (water moves in / out) by osmosis ; 4 (water moves) from a higher water potential to a lower water potential ; 5 solute concentration of cells is equivalent to value from graph where line intersects x-axis ; 4(a)(iii) any 2 of: 2 1 turgor pressure decreases up to concentration of 0.75 and then levels off (at zero) / AW ; 2 because as concentration increases, water content of cells is less / AW ; 3 below 0.75, membrane presses / touches cell wall / AW ; 4 over 0.75, cell membrane peels away from cell wall / cells has become plasmolysed / AW ; 4(b)(i) any 2 of: 2 1 water would (naturally) move into chamber A / from chamber B / from freshwater to sea water / AW ; 2 as the water potential of B is higher than A / water would down the water potential gradient / water is being forced against the water potential gradient / AW ; 3 so pressure needs to be greater than osmotic force / pressure / AW ; 4 salts cannot pass through the membrane / only water can pass through the membrane / AW ; 4(b)(ii) any 3 of: 3 1 salinity of the sea increases / water potential decreases ; 2 affects osmoconformer species / AW ; 3 water would be lost (from organisms) / cause dehydration / AW ; 4 alters density of water / salinity gradients / haloclines / AW ; 5 (high salinity) would reduce oxygen content of water / AW ; 6 causing organisms to suffocate / reduces respiration / AW ; 7 (the salt solution) may also contain high concentrations of toxins / AW ; 8 AVP ;
This question in 9693/43 May/June 2025
Q50 · Artificial reefs are often created by sinking old ships 9693/41 Oct/Nov 2025
1 Artificial reefs are often created by sinking old ships. (a) Explain how artificial reefs can help to rehabilitate fish stocks. … … … … … … [3] (b) Scientists investigated the risk of heavy metal ions leaking from artificial reefs into sea water. Bags of mussels were placed on a sunken metal ship. Bags of mussels were also placed at an area one kilometre from the ship as a control. After six months, the mean concentrations of chromium ions, lead ions and zinc ions in the mussels were determined. The results are shown in Table 1.1. Table 1.1 heavy metal ion concentration in mussels on concentration in control ship / mg kg–1 mussels / mg kg–1 mean standard deviation mean standard deviation chromium 1.40 0.47 0.67 0.10 lead 0.36 0.05 0.23 0.04 zinc 178.00 44.40 152.00 29.50 (i) Calculate the percentage difference in the mean concentration of chromium ions in the mussels on the ship compared with the mean concentration of chromium ions in the control mussels. Give your answer to two significant figures. Show your working. … % [3] (ii) Describe the differences in concentrations of heavy metal ions in the mussels on the ship compared with the concentrations of heavy metal ions in the control mussels. … … … … … … [3] (c) Fig. 1.1 shows the concentration of lead ions in the tissues of consumers that feed on mussels containing different concentrations of lead ions. 0.70 0.60 0.50 concentration of 0.40 lead ions in tissues of consumers 0.30 / mg kg–1 0.20 0.10 0.00 0.00 0.10 0.20 0.30 0.40 concentration of lead ions in tissues of mussels / mg kg–1 Fig. 1.1 (i) Summarise the effect of increasing concentration of lead ions in the tissues of mussels on the concentration of lead ions in the tissues of consumer organisms. … … … … [2] Table 1.1 heavy metal ion concentration in mussels on concentration in control ship / mg kg–1 mussels / mg kg–1 mean standard deviation mean standard deviation chromium 1.40 0.47 0.67 0.10 lead 0.36 0.05 0.23 0.04 zinc 178.00 44.40 152.00 29.50 0.70 0.60 0.50 concentration of 0.40 lead ions in tissues of consumers 0.30 / mg kg–1 0.20 0.10 0.00 0.00 0.10 0.20 0.30 0.40 concentration of lead ions in tissues of mussels / mg kg–1 Fig. 1.1 (ii) Use the information in Table 1.1 and Fig. 1.1 (repeated above) to predict the mean concentration of lead ions in the tissues of consumer organisms that eat mussels from the ship. … mg kg–1 [1] (iii) Use the information in Table 1.1 and Fig. 1.1 (repeated above) to explain the risks of using ships as artificial reefs. … … … … … … [4] [Total: 16]
16 marks
Mark scheme: Question Answer Marks 1(a) any 3 of: 3 1 act as a, substrate (for sessile organisms) / habitat ; 2 create food webs / food chains ; 3 more food availability / more niches / AW ; 4 shelter for fish / protection from predators / AW ; 5 nursery / breeding, grounds / AW ; 1(b)(i) 1.40 – 0.67 = 0.73 ; 3 0.73 / 0.67 – 100 = 108.958… ; 110(%) ;;; (3 marks) 108.958… (2 marks) A 1 mark for 0.73, 1.40–0.67, or division by 0.67 OR 1.40 – 0.67 = 0.73 ; 0.73 / 1.40 – 100 = 52.14…(%) ; 52(%) ;;; (3 marks) 0.5214… ;; (2 marks) A 1 mark for 0.73, 1.40–0.67, or division by 1.40 OR 0.73 / 1.035 100 = 70.53… ; A 70(%) ;;; (3 marks) 70.53… ;; (2 marks) A 1 mark for 0.73, 1.40–0.67, or division by 1.035 1(b)(ii) any 3 of: 3 1 higher in all (on ship compared with control) / ORA ; 2 zinc has highest levels (compared with chromium and lead) / lead has lowest levels / AW ; 3 chromium and lead are significantly higher / zinc is not significantly higher ; 4 correct ref to s.d. overlaps ; 5 credit correct manipulation of data ; 6 chromium has, highest relative / percentage increase ; 1(c)(i) increase / positive correlation / as lead increases in mussels, lead increases in consumers ; 2 steep increase then levels off ; 1(c)(ii) answer between 0.64–0.65 ; 1 1(c)(iii) any 4 of: 4 1 mussels / low trophic level organisms, absorb heavy metal ions / absorb chromium / absorb lead / absorb zinc / AW ; 2 heavy metal ions are (often) toxic / AW ; 3 (heavy metal ions) bioaccumulate in organisms ; 4 (heavy metal ions) are not excreted / cannot be broken down / non-biodegradable ; 5 (lead / chromium / heavy metal ions) passed onto consumers / AW ; 6 biomagnification occurs along food chain / AW ; 7 because consumers eat several of lower levels ; 8 AVP ;
This question in 9693/41 Oct/Nov 2025
Q51 · Artificial reefs are often created by sinking old ships 9693/42 Oct/Nov 2025
1 Artificial reefs are often created by sinking old ships. (a) Explain how artificial reefs can help to rehabilitate fish stocks. … … … … … … [3] (b) Scientists investigated the risk of heavy metal ions leaking from artificial reefs into sea water. Bags of mussels were placed on a sunken metal ship. Bags of mussels were also placed at an area one kilometre from the ship as a control. After six months, the mean concentrations of chromium ions, lead ions and zinc ions in the mussels were determined. The results are shown in Table 1.1. Table 1.1 heavy metal ion concentration in mussels on concentration in control ship / mg kg–1 mussels / mg kg–1 mean standard deviation mean standard deviation chromium 1.40 0.47 0.67 0.10 lead 0.36 0.05 0.23 0.04 zinc 178.00 44.40 152.00 29.50 (i) Calculate the percentage difference in the mean concentration of chromium ions in the mussels on the ship compared with the mean concentration of chromium ions in the control mussels. Give your answer to two significant figures. Show your working. … % [3] (ii) Describe the differences in concentrations of heavy metal ions in the mussels on the ship compared with the concentrations of heavy metal ions in the control mussels. … … … … … … [3] (c) Fig. 1.1 shows the concentration of lead ions in the tissues of consumers that feed on mussels containing different concentrations of lead ions. 0.70 0.60 0.50 concentration of 0.40 lead ions in tissues of consumers 0.30 / mg kg–1 0.20 0.10 0.00 0.00 0.10 0.20 0.30 0.40 concentration of lead ions in tissues of mussels / mg kg–1 Fig. 1.1 (i) Summarise the effect of increasing concentration of lead ions in the tissues of mussels on the concentration of lead ions in the tissues of consumer organisms. … … … … [2] Table 1.1 heavy metal ion concentration in mussels on concentration in control ship / mg kg–1 mussels / mg kg–1 mean standard deviation mean standard deviation chromium 1.40 0.47 0.67 0.10 lead 0.36 0.05 0.23 0.04 zinc 178.00 44.40 152.00 29.50 0.70 0.60 0.50 concentration of 0.40 lead ions in tissues of consumers 0.30 / mg kg–1 0.20 0.10 0.00 0.00 0.10 0.20 0.30 0.40 concentration of lead ions in tissues of mussels / mg kg–1 Fig. 1.1 (ii) Use the information in Table 1.1 and Fig. 1.1 (repeated above) to predict the mean concentration of lead ions in the tissues of consumer organisms that eat mussels from the ship. … mg kg–1 [1] (iii) Use the information in Table 1.1 and Fig. 1.1 (repeated above) to explain the risks of using ships as artificial reefs. … … … … … … [4] [Total: 16]
16 marks
Mark scheme: Question Answer Marks 1(a) any 3 of: 3 1 act as a, substrate (for sessile organisms) / habitat ; 2 create food webs / food chains ; 3 more food availability / more niches / AW ; 4 shelter for fish / protection from predators / AW ; 5 nursery / breeding, grounds / AW ; 1(b)(i) 1.40 – 0.67 = 0.73 ; 3 0.73 / 0.67 – 100 = 108.958… ; 110(%) ;;; (3 marks) 108.958… (2 marks) A 1 mark for 0.73, 1.40–0.67, or division by 0.67 OR 1.40 – 0.67 = 0.73 ; 0.73 / 1.40 – 100 = 52.14…(%) ; 52(%) ;;; (3 marks) 0.5214… ;; (2 marks) A 1 mark for 0.73, 1.40–0.67, or division by 1.40 OR 0.73 / 1.035 100 = 70.53… ; A 70(%) ;;; (3 marks) 70.53… ;; (2 marks) A 1 mark for 0.73, 1.40–0.67, or division by 1.035 1(b)(ii) any 3 of: 3 1 higher in all (on ship compared with control) / ORA ; 2 zinc has highest levels (compared with chromium and lead) / lead has lowest levels / AW ; 3 chromium and lead are significantly higher / zinc is not significantly higher ; 4 correct ref to s.d. overlaps ; 5 credit correct manipulation of data ; 6 chromium has, highest relative / percentage increase ; 1(c)(i) increase / positive correlation / as lead increases in mussels, lead increases in consumers ; 2 steep increase then levels off ; 1(c)(ii) answer between 0.64–0.65 ; 1 1(c)(iii) any 4 of: 4 1 mussels / low trophic level organisms, absorb heavy metal ions / absorb chromium / absorb lead / absorb zinc / AW ; 2 heavy metal ions are (often) toxic / AW ; 3 (heavy metal ions) bioaccumulate in organisms ; 4 (heavy metal ions) are not excreted / cannot be broken down / non-biodegradable ; 5 (lead / chromium / heavy metal ions) passed onto consumers / AW ; 6 biomagnification occurs along food chain / AW ; 7 because consumers eat several of lower levels ; 8 AVP ;
This question in 9693/42 Oct/Nov 2025
Q52 · Artificial reefs are often created by sinking old ships 9693/43 Oct/Nov 2025
1 Artificial reefs are often created by sinking old ships. (a) Explain how artificial reefs can help to rehabilitate fish stocks. … … … … … … [3] (b) Scientists investigated the risk of heavy metal ions leaking from artificial reefs into sea water. Bags of mussels were placed on a sunken metal ship. Bags of mussels were also placed at an area one kilometre from the ship as a control. After six months, the mean concentrations of chromium ions, lead ions and zinc ions in the mussels were determined. The results are shown in Table 1.1. Table 1.1 heavy metal ion concentration in mussels on concentration in control ship / mg kg–1 mussels / mg kg–1 mean standard deviation mean standard deviation chromium 1.40 0.47 0.67 0.10 lead 0.36 0.05 0.23 0.04 zinc 178.00 44.40 152.00 29.50 (i) Calculate the percentage difference in the mean concentration of chromium ions in the mussels on the ship compared with the mean concentration of chromium ions in the control mussels. Give your answer to two significant figures. Show your working. … % [3] (ii) Describe the differences in concentrations of heavy metal ions in the mussels on the ship compared with the concentrations of heavy metal ions in the control mussels. … … … … … … [3] (c) Fig. 1.1 shows the concentration of lead ions in the tissues of consumers that feed on mussels containing different concentrations of lead ions. 0.70 0.60 0.50 concentration of 0.40 lead ions in tissues of consumers 0.30 / mg kg–1 0.20 0.10 0.00 0.00 0.10 0.20 0.30 0.40 concentration of lead ions in tissues of mussels / mg kg–1 Fig. 1.1 (i) Summarise the effect of increasing concentration of lead ions in the tissues of mussels on the concentration of lead ions in the tissues of consumer organisms. … … … … [2] Table 1.1 heavy metal ion concentration in mussels on concentration in control ship / mg kg–1 mussels / mg kg–1 mean standard deviation mean standard deviation chromium 1.40 0.47 0.67 0.10 lead 0.36 0.05 0.23 0.04 zinc 178.00 44.40 152.00 29.50 0.70 0.60 0.50 concentration of 0.40 lead ions in tissues of consumers 0.30 / mg kg–1 0.20 0.10 0.00 0.00 0.10 0.20 0.30 0.40 concentration of lead ions in tissues of mussels / mg kg–1 Fig. 1.1 (ii) Use the information in Table 1.1 and Fig. 1.1 (repeated above) to predict the mean concentration of lead ions in the tissues of consumer organisms that eat mussels from the ship. … mg kg–1 [1] (iii) Use the information in Table 1.1 and Fig. 1.1 (repeated above) to explain the risks of using ships as artificial reefs. … … … … … … [4] [Total: 16]
16 marks
Mark scheme: Question Answer Marks 1(a) any 3 of: 3 1 act as a, substrate (for sessile organisms) / habitat ; 2 create food webs / food chains ; 3 more food availability / more niches / AW ; 4 shelter for fish / protection from predators / AW ; 5 nursery / breeding, grounds / AW ; 1(b)(i) 1.40 – 0.67 = 0.73 ; 3 0.73 / 0.67 – 100 = 108.958… ; 110(%) ;;; (3 marks) 108.958… (2 marks) A 1 mark for 0.73, 1.40–0.67, or division by 0.67 OR 1.40 – 0.67 = 0.73 ; 0.73 / 1.40 – 100 = 52.14…(%) ; 52(%) ;;; (3 marks) 0.5214… ;; (2 marks) A 1 mark for 0.73, 1.40–0.67, or division by 1.40 OR 0.73 / 1.035 100 = 70.53… ; A 70(%) ;;; (3 marks) 70.53… ;; (2 marks) A 1 mark for 0.73, 1.40–0.67, or division by 1.035 1(b)(ii) any 3 of: 3 1 higher in all (on ship compared with control) / ORA ; 2 zinc has highest levels (compared with chromium and lead) / lead has lowest levels / AW ; 3 chromium and lead are significantly higher / zinc is not significantly higher ; 4 correct ref to s.d. overlaps ; 5 credit correct manipulation of data ; 6 chromium has, highest relative / percentage increase ; 1(c)(i) increase / positive correlation / as lead increases in mussels, lead increases in consumers ; 2 steep increase then levels off ; 1(c)(ii) answer between 0.64–0.65 ; 1 1(c)(iii) any 4 of: 4 1 mussels / low trophic level organisms, absorb heavy metal ions / absorb chromium / absorb lead / absorb zinc / AW ; 2 heavy metal ions are (often) toxic / AW ; 3 (heavy metal ions) bioaccumulate in organisms ; 4 (heavy metal ions) are not excreted / cannot be broken down / non-biodegradable ; 5 (lead / chromium / heavy metal ions) passed onto consumers / AW ; 6 biomagnification occurs along food chain / AW ; 7 because consumers eat several of lower levels ; 8 AVP ;
This question in 9693/43 Oct/Nov 2025
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