Conservation of marine ecosystems — Paper 2 · A Level Marine Science 9693

3 (a) Describe the factors needed for tropical coral reef growth. … … … … … … [3] (b) Describe the scientific methods that can be used to reconstruct the history of a coral reef. … … … … … … … … … … [5] (c) Discuss the impacts that tropical coral reef destruction can have on human coastal communities. … … … … … … … … … … … … … … [7] [Total: 15]

15 marks

Mark scheme: 3(a) any 3 from: warm water temperature ; suitable depth / within 20 m of surface ; suitable substrate for attachment of coral larvae ; high / sufficient, light intensity ; ref. to clarity / turbidity of water ; suitable pH ; Question Answer Marks 3(b) any 5 from: geomorphological analysis ; drilling for cores of reef substrate ; from different depths in reef ; analysis of / studying bands in core samples ; (idea of) radiocarbon / 14C dating ; ref. to 14C incorporated into carbonate ; ref. to half life / decay of 14C ; ref. to ratio of 14C to 12C indicates age of coral ; 5 3(c) any 7 from: (coral reefs) absorb wave energy / dissipate wave energy ; reefs reduce wave action / reduce size or strength of waves / slow down waves ; increased erosion of shores AW ; reduced protection for coastal properties ; reduced protection of coastal anchorages / boats ; reduced protection of ecosystems ; reduced tourism; reduced, food from, (harvesting / fishing) ; reduced income / profit ; reduced protection from extreme weather effects e.g. cyclones / hurricanes ; cost of building breakwaters / sea walls ; AVP ; 7

This question in 9693/22 May/June 2021

3 (a) Describe the factors needed for tropical coral reef growth. … … … … … … [3] (b) Describe the scientific methods that can be used to reconstruct the history of a coral reef. … … … … … … … … … … [5] (c) Discuss the impacts that tropical coral reef destruction can have on human coastal communities. … … … … … … … … … … … … … … [7] [Total: 15]

15 marks

Mark scheme: 3(a) any 3 from: warm water temperature ; suitable depth / within 20 m of surface ; suitable substrate for attachment of coral larvae ; high / sufficient, light intensity ; ref. to clarity / turbidity of water ; suitable pH ; Question Answer Marks 3(b) any 5 from: geomorphological analysis ; drilling for cores of reef substrate ; from different depths in reef ; analysis of / studying bands in core samples ; (idea of) radiocarbon / 14C dating ; ref. to 14C incorporated into carbonate ; ref. to half life / decay of 14C ; ref. to ratio of 14C to 12C indicates age of coral ; 5 3(c) any 7 from: (coral reefs) absorb wave energy / dissipate wave energy ; reefs reduce wave action / reduce size or strength of waves / slow down waves ; increased erosion of shores AW ; reduced protection for coastal properties ; reduced protection of coastal anchorages / boats ; reduced protection of ecosystems ; reduced tourism; reduced, food from, (harvesting / fishing) ; reduced income / profit ; reduced protection from extreme weather effects e.g. cyclones / hurricanes ; cost of building breakwaters / sea walls ; AVP ; 7

This question in 9693/23 May/June 2021

1 Artificial reefs are widely used to regenerate coral reef ecosystems. Artificial reefs can be made using 3D printing technology. This technology makes exact copies of the shape and structure of real coral skeletons. Fig. 1.1 shows an artificial coral skeleton made using this technology. Fig. 1.1 (a) Scientists investigated how damselfish (small reef fish) behave when introduced to artificial coral skeletons made of different types of material. Four different types of material were used, A–D, in addition to natural coral as a control. Individual damselfish were introduced to tanks containing all five types of coral skeletons. A total of 44 fish were used. They were able to move freely between the different types of coral skeleton, and the time spent associating with each was recorded. (i) Suggest two variables that the scientists need to control to obtain reliable results. 1 … … 2 … … [2] (ii) Fig. 1.2 shows the percentage of time the damselfish spent associating with each type of coral skeleton. 20 15 percentage of time damselfish 10 associate with coral skeleton 5 0 natural A B C D type of coral material Fig. 1.2 State a conclusion regarding the behaviour of the fish around the coral skeletons. Use the information in Fig. 1.2 to support your answer. … … … … … … [3] (iii) Suggest reasons why small reef fish such as damselfish are dependent on coral for their survival. … … … … [2] (b) Scientists then investigated the settlement and growth of coral polyp larvae on artificial coral skeletons. Equal numbers of coral polyp larvae were introduced into separate tanks containing each type of artificial coral skeleton. The percentage of larvae attached to each type of coral skeleton was recorded over a 14-day period, and the growth rate of those that attached was calculated. Fig. 1.3 shows the percentage of larvae attached to each type of coral skeleton material. 30 Key A B 25 C D 20 percentage of larvae attached 15 10 5 1 2 3 4 5 6 7 8 9 10 11 12 13 14 day Fig. 1.3 Table 1.1 shows the mean growth rate of attached coral polyp larvae. Table 1.1 coral skeleton mean growth rate of material coral polyp larvae / mm2 per week A 0.078 B 0.201 C 0.211 D 0.162 Discuss which of the materials A–D is best to use for the growth of coral polyp larvae. Use the results shown in Fig. 1.3 and Table 1.1 to support your answer. … … … … … … [3] (c) The scientists concluded that 3D-printed coral skeletons can be used for regenerating coral reef ecosystems. Evaluate the extent to which the results from this investigation support this conclusion. … … … … … … [3] (d) Fig. 1.4 shows a damselfish similar to those used in the investigation. Fig. 1.4 (i) Make a large drawing of the damselfish in the space below. [4] (ii) Label the caudal fin and the dorsal fin on your drawing. [1] [Total: 18]

18 marks

Mark scheme: 1(a)(i) any 2 from: length of time (observed for) ; size of (coral) samples ; spacing of (coral) samples ; any water quality factor, e.g. pH / temperature / salinity / nutrients ;; (idea of) illumination / light intensity / sunlight ; size of tank ; same, size / age / species fish ; colour of coral ; (idea of avoiding bias towards a sample) distance fish introduced / released, to the coral ; 1(a)(ii) any 2 from: samples A, B or C have higher (association) time than natural sample ; sample (B and) C have greatest (increase in association) time / spend largest amount of time with coral C (and B) ; sample D has same, effect / (association) time as natural sample ; AND correct use of data from graph to support answer ; 3 1(a)(iii) any 2 from: food source / eat zooxanthellae ; shelter / protection (from, predators / water movement) ; (idea of) reproductive site / nursery ; 2 Question Answer Marks 1(b) any 3 from: (from day 7) material D has the greatest percentage of larvae attaching… ; …but does not have the highest mean growth rate / relatively high growth rate ; sample(s) (B and) C have the highest growth rate(s) ; sample A has lowest percentage settling and lowest growth rate ; materials B and/or D (greatest percentage of larvae attaching) and are stable / C or D are the lowest percentage of larvae attaching and are decreasing ; insufficient length of time of investigation because percentage of C settling is decreasing ; correct use of manipulated data from table or graph to support answer ; 3 1(c) any 3 from: (supports conclusion) as fish associate with artificial coral at least as much as natural ; (supports conclusion) as some samples allow larvae to, settle / grow ; 44 individual fish used is a high number of repeats ; (however) coral polyps may grow faster / attach better, on natural coral / no data on natural coral growth rate ; (however) larvae survival only monitored for 14 days ; (however) only one species / type of fish studied ; (however) no information on number / type of coral larvae used ; should conduct further research in natural habitat rather than tanks ; (idea of longer time period needed) research for longer than two weeks (idea of) research required on natural (bleached) coral to compare (settlement / growth rates) ; AVP ; 3 Question Answer Marks 1(d)(i) clear outline ; suitable size ; in proportion ; detail – must include all visible fins and outline of three black vertical areas in approximately correct positions and the eye ; 4 1(d)(ii) both fins labelled correctly either on the drawing or photograph ; 1

This question in 9693/21 May/June 2022

3 Mangrove forests are globally threatened ecosystems. (a) Describe one adaptation of the red mangrove tree (Rhizophora mangle) for its environment. … … [1] (b) Mangrove forests can be regenerated by growing mangrove seedlings in controlled conditions and planting them into their native forest ecosystems. Scientists investigated the survival of three species of mangrove seedlings (species X, Y and Z) in different salinities of sea water. 50 seedlings of each species were grown in three different salinities: • low salinity (4 ppt) • moderate salinity (16 ppt) • high salinity (34 ppt). The seedlings were kept at these salinities for 30 weeks. The percentage of seedlings surviving was recorded every two weeks. (i) Suggest how the scientists created the different salinity treatments. … … … … [2] (ii) Describe two ways in which this investigation could be improved. 1 … … 2 … … [2] (c) Fig. 3.1 shows the results from this investigation. Key low salinity moderate salinity high salinity 100 80 percentage 60 of seedlings surviving 40 20 species X 0 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 time / weeks 100 80 percentage 60 of seedlings surviving 40 20 species Y 0 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 time / weeks 100 80 percentage 60 of seedlings surviving 40 20 species Z 0 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 time / weeks Fig. 3.1 (i) Describe how the percentage of seedlings surviving in each salinity was calculated. … … [1] (ii) Calculate how many seedlings of species Z survived the first 10 weeks of the investigation in the highest salinity. Show your working. … [2] (d) Fig. 3.2 shows three locations, A, B and C, in a delta. shoreline C A B river water flow delta channels Fig. 3.2 Use the information in Fig. 3.1 and Fig. 3.2 to suggest which species is best adapted to survive at location A. Explain your answer. … … … … … … [3] (e) At the delta, seedlings will be exposed to changes in the tidal cycle. Suggest why the tidal cycle will cause variations in the salinity of the water at location B. … … … … … … [3] (f) The conservation of mangrove ecosystems is important for human populations. State two benefits. 1 … … 2 … … [2] [Total: 16]

16 marks

Mark scheme: 3(a) any 1 of: prop roots ; salt exclusion by roots / roots help filter salt water ; viviparous reproduction / propagules ; 1 3(b)(i) either: known mass of, sodium chloride / salt ; dissolved in, known / stated, volume / mass, of water ; or: use, (stock) solution / sea water, of known concentration / 34 ppt ; and dilute known volume with known volume of water ; or: add salt to, distilled / fresh, water OR (dilute) seawater with distilled / fresh, water + using a, salinometer / refractometer ; until it reaches the correct salinity ; 2 3(b)(ii) any 2 of: (investigate for) longer than 30 weeks ; (investigate) more (than 3) species ; (investigate) a greater range of salinities ; more seedlings ; 2 3(c)(i) surviving number / 50,  100 ; 1 Question Answer Marks 3(c)(ii) 48  100  50 OR 48  is 48 in 100 so 24 in 50 OR 24 / 50  0.48 OR 48  2 ; 24 ; 2 3(d) species X + highest survival rate in most saline water ; Site A highest salinity (closest to sea / shoreline) ; Site A will experience, least mixing with fresh water / fresh water spread out over a wider area / more time mixed with incoming sea water AW ; 3 3(e) (idea of) high tide increasing salinity / water becomes more saline at high tide / as tide comes in more salty water will be at B / as tide goes out more fresh water will be at B / ORA ; (idea of) increased (proportion of) sea water to freshwater / ORA ; (idea of) spring tides cause greater increase in salinity (at high water) / ORA for neap tides ; 3 3(f) any 2 of: tourism ; food sources / nursery grounds for fish / fisheries / provide nutrients ; (source of) timber ; coastal protection / flooding / reduce wave energy / prevent erosion ; (source of) fuel ; (source of) (antifungal) drug / medicines / medical use ; 2

This question in 9693/21 May/June 2023

1 Fig. 1.1 shows the shell of a common dogwhelk, Nucella lapillus, which is adapted to live on rocky shores. Fig. 1.1 (a) State a mineral that is required for the formation of shells. … [1] (b) Make a large drawing of the shell shown in Fig. 1.1. Do not label your drawing. [4] (c) Dogwhelks use a large muscular foot to cling to the rocks on rocky shores. A scientist investigated the shape of dogwhelk shells on different shore types. They analysed dogwhelks from an exposed rocky shore with high wave action, and a sheltered rocky shore with low wave action. 100 dogwhelks from each shore were sampled, and the following measurements were recorded: • total shell length • shell aperture length. Fig. 1.2 shows how these measurements were recorded. total shell length shell aperture length Fig. 1.2 Table 1.1 shows the mean results of the investigation. Table 1.1 shore type mean total shell length / mm mean shell aperture length / mm exposed rocky shore 24.6 12.5 sheltered rocky shore 26.1 11.9 (i) Describe how the mean total shell lengths were calculated. … … [1] (ii) The scientist calculated the ratio of mean total shell length : mean shell aperture length for the dogwhelks on each shore. Complete Table 1.2 by calculating the ratio for the sheltered rocky shore. Table 1.2 shore type ratio of mean total shell length : mean shell aperture length exposed rocky shore 1.97 : 1 sheltered rocky shore [1] (iii) Compare the shapes of dogwhelk shells on each shore type, using data from Table 1.1 and Table 1.2. Suggest reasons for any differences. … … … … … … … … [4] (d) During the investigation the scientist noticed that the dogwhelks showed variation in the colour of their shells, some being darker than others. The scientist also noticed that the darker‑shelled individuals were located in more shaded parts of the rocky shore. They suggested the following hypothesis: ‘Lighter-shelled dogwhelks can tolerate higher exposure to sunlight.’ A further investigation was then carried out. Light and dark dogwhelks on an area of shore were all marked with a small spot of paint on the shell. The paint fades on exposure to sunlight. After three days the degree of fading was recorded, using a score of 1 to 10. Table 1.3 shows the results. Table 1.3 paint fading score number of lighter-shelled number of darker-shelled dogwhelks dogwhelks 1 (least faded) 0 0 2 5 4 3 33 34 4 58 14 5 40 11 6 30 7 7 8 3 8 22 5 9 2 0 10 (most faded) 4 0 Discuss whether the results in Table 1.3 support the scientist’s hypothesis. … … … … … … [3] (e) Suggest one way the scientist ensured their methods were ethical. … … [1] [Total: 15]

15 marks

Mark scheme: 1(a) calcium ; 1 1(b) clear outline ; suitable size ; in proportion ; detail ; 4 1(c)(i) add together all shell lengths (for one / each shore) AND divide by 100 ; 1 1(c)(ii) 2.19 : 1 ; 1 1(c)(iii) any 4 of: length : aperture ratio lower on exposed shore / ORA ; shell aperture is larger (relative to length) on exposed shore / ORA ; larger foot ; stronger attachment to rock ; increases, survival chance / ability to stay attached, with stronger wave action ; (mean) shell length greater on sheltered shore / ORA ; because dogwhelks have higher life expectancy so grow bigger ; feeding efficiency greater on sheltered shore ; 4 Question Answer Marks 1(d) any 3 of: (yes because…) more light-shelled dogwhelks with a higher paint fading score / ORA ; suggesting they spent more time exposed to the Sun / ORA ; (no because) peak numbers are very close together ; sample size of dark-shelled dogwhelks much smaller / less than half ; ref. to limited scope of investigation e.g. one area / small numbers / only ; 3 days ; other factor may affect fading of paint e.g. saltwater ; idea of, correlation not causation / a different factor may be involved ; 3 1(e) any 1 of: taking care not to damage dogwhelks / other shore organisms ; taking care to, replace dogwhelks in same place / allow dogwhelks to reattach properly ; using a paint that does not harm the dogwhelks / environment ; 1

This question in 9693/22 May/June 2023

1 Fig. 1.1 shows the shell of a common dogwhelk, Nucella lapillus, which is adapted to live on rocky shores. Fig. 1.1 (a) State a mineral that is required for the formation of shells. … [1] (b) Make a large drawing of the shell shown in Fig. 1.1. Do not label your drawing. [4] (c) Dogwhelks use a large muscular foot to cling to the rocks on rocky shores. A scientist investigated the shape of dogwhelk shells on different shore types. They analysed dogwhelks from an exposed rocky shore with high wave action, and a sheltered rocky shore with low wave action. 100 dogwhelks from each shore were sampled, and the following measurements were recorded: • total shell length • shell aperture length. Fig. 1.2 shows how these measurements were recorded. total shell length shell aperture length Fig. 1.2 Table 1.1 shows the mean results of the investigation. Table 1.1 shore type mean total shell length / mm mean shell aperture length / mm exposed rocky shore 24.6 12.5 sheltered rocky shore 26.1 11.9 (i) Describe how the mean total shell lengths were calculated. … … [1] (ii) The scientist calculated the ratio of mean total shell length : mean shell aperture length for the dogwhelks on each shore. Complete Table 1.2 by calculating the ratio for the sheltered rocky shore. Table 1.2 shore type ratio of mean total shell length : mean shell aperture length exposed rocky shore 1.97 : 1 sheltered rocky shore [1] (iii) Compare the shapes of dogwhelk shells on each shore type, using data from Table 1.1 and Table 1.2. Suggest reasons for any differences. … … … … … … … … [4] (d) During the investigation the scientist noticed that the dogwhelks showed variation in the colour of their shells, some being darker than others. The scientist also noticed that the darker‑shelled individuals were located in more shaded parts of the rocky shore. They suggested the following hypothesis: ‘Lighter-shelled dogwhelks can tolerate higher exposure to sunlight.’ A further investigation was then carried out. Light and dark dogwhelks on an area of shore were all marked with a small spot of paint on the shell. The paint fades on exposure to sunlight. After three days the degree of fading was recorded, using a score of 1 to 10. Table 1.3 shows the results. Table 1.3 paint fading score number of lighter-shelled number of darker-shelled dogwhelks dogwhelks 1 (least faded) 0 0 2 5 4 3 33 34 4 58 14 5 40 11 6 30 7 7 8 3 8 22 5 9 2 0 10 (most faded) 4 0 Discuss whether the results in Table 1.3 support the scientist’s hypothesis. … … … … … … [3] (e) Suggest one way the scientist ensured their methods were ethical. … … [1] [Total: 15]

15 marks

Mark scheme: 1(a) calcium ; 1 1(b) clear outline ; suitable size ; in proportion ; detail ; 4 1(c)(i) add together all shell lengths (for one / each shore) AND divide by 100 ; 1 1(c)(ii) 2.19 : 1 ; 1 1(c)(iii) any 4 of: length : aperture ratio lower on exposed shore / ORA ; shell aperture is larger (relative to length) on exposed shore / ORA ; larger foot ; stronger attachment to rock ; increases, survival chance / ability to stay attached, with stronger wave action ; (mean) shell length greater on sheltered shore / ORA ; because dogwhelks have higher life expectancy so grow bigger ; feeding efficiency greater on sheltered shore ; 4 Question Answer Marks 1(d) any 3 of: (yes because…) more light-shelled dogwhelks with a higher paint fading score / ORA ; suggesting they spent more time exposed to the Sun / ORA ; (no because) peak numbers are very close together ; sample size of dark-shelled dogwhelks much smaller / less than half ; ref. to limited scope of investigation e.g. one area / small numbers / only ; 3 days ; other factor may affect fading of paint e.g. saltwater ; idea of, correlation not causation / a different factor may be involved ; 3 1(e) any 1 of: taking care not to damage dogwhelks / other shore organisms ; taking care to, replace dogwhelks in same place / allow dogwhelks to reattach properly ; using a paint that does not harm the dogwhelks / environment ; 1

This question in 9693/23 May/June 2023

1 Mangrove forests are important ecosystems. (a) Explain the term ecosystem. … … … … [2] (b) Fig. 1.1 shows the area of mangrove forest in ten countries and the areas of mangrove forest that are protected and unprotected. Key protected mangrove forest unprotected mangrove forest 30 000 25 000 20 000 area of mangrove 15 000 forest / km2 10 000 5000 0 IndonesiaBrazilAustraliaMexicoNigeriaMalaysiaMyanmar GuineaBangladeshCuba New Papua countries Fig. 1.1 (i) State the name of the country which protects the greatest percentage of its mangrove forest. … [1] (ii) Calculate the percentage of mangrove forest in Mexico that is protected. Show your working. … % [2] (iii) State two major threats to mangrove forests. 1 … 2 … [2] (c) Some species of macroalgae grow attached to the roots of mangrove trees. Scientists planned an investigation to compare the rate of photosynthesis at different light intensities in two of these species of macroalgae. (i) State the word equation for photosynthesis. … [1] Fig. 1.2 shows their experimental set-up. This closed system is used to fully contain a standardised volume of water which is circulated. An oxygen sensor recorded oxygen concentration in the water. The whole apparatus was submerged into a much larger tank of sea water for the investigation. circulation pump sealed plastic dome macroalgae grid sealed plastic base dissolved oxygen sensor Fig. 1.2 (ii) Identify the dependent variable. … [1] (iii) Suggest two variables that should be standardised in this investigation. 1 … 2 … [1] (iv) Suggest how the light intensity was changed. … … [1] (v) The scientists allowed the macroalgae to photosynthesise for 8 minutes in the closed system. They then exchanged the water in the closed system with some of the water in the surrounding tank, before beginning to collect results. Suggest one reason the scientists exchanged the water. … … [1] Table 1.1 shows the results from the investigation. Table 1.1 light intensity oxygen production / μmol mm–2 min–1 / arbitrary units macroalgae species A macroalgae species B 50 650 210 350 1750 580 600 2410 1530 900 2950 3090 1200 2910 3310 (vi) Plot a graph of the two sets of data in Table 1.1 on the grid below and draw an appropriate line for each data set. Complete the axes for the graph. oxygen production / … … [5] (vii) The two species of macroalgae used in the investigation are found at different depths on the mangrove tree roots. Use Table 1.1 to explain the expected depth distribution of the two species of macroalgae on the mangrove tree roots. … … … … … … [3] (viii) At a light intensity of zero the oxygen level decreased during the investigation. Explain this observation. … … … … [2] [Total: 22]

22 marks

Mark scheme: Question Answer Marks 1(a) interactions between, different species / community / biotic factors ; 2 and their (physical), environment / habitat / abiotic factors ; 1(b)(i) Bangladesh ; 1 1(b)(ii) correct reading of two figures from graph ; 2 (protected area  total area)  100 = (value between) 61.34%–70.41% ; 1(b)(iii) any 2 from: 2 global warming / climate change / temperature change ; over-harvesting / deforestation ; storm damage ; change in land use or named example e.g. shrimp farms ; 1(c)(i) carbon dioxide + water → glucose + oxygen ; 1 1(c)(ii) oxygen concentration ; 1 1(c)(iii) any 2 from: 1 temperature (of water) / size, mass, length, of algae / salinity / carbon dioxide / water, type or quality / volume of water or water flow or flow rate (through system) / pH / initial oxygen concentration / colour of light or wavelength ; 1(c)(iv) lamp / light source, moved different distances (from the apparatus) ; 1 1(c)(v) any 1 from: 1 add additional carbon dioxide / remove built up oxygen ; to acclimatise the macroalgae to the conditions before collecting results OWTTE ; 1(c)(vi) both axes labelled with units ; 5 (suitable) linear scale ; points plotted  ½ small square with x or dot in circle ; appropriate lines drawn for both sets of data ; key to identify the 2 data sets ; 1(c)(vii) Any 3 from: 3 species B closer to the surface / species A, can extend to greater depth ; (as species B), require a higher light intensity to photosynthesise / higher rate of photosynthesis than A at shallow depths / lower rate of photosynthesis than A at lower light intensities ORA ; correct ref. to data comparison or manipulation (from their graph) ; the lines cross over at stated light intensity (from their graph) OR the same rate (of photosynthesis) at stated light intensity ; species B may be found at a narrower range of depths / ORA ; both species found near the surface / at high light intensities ; 1(c)(viii) no photosynthesis occurring (as no light) ; 2 respiration uses oxygen ;

This question in 9693/23 Oct/Nov 2023

1 Blue crabs are crustaceans. Fig. 1.1 shows a blue crab. Fig. 1.1 (a) (i) On Fig. 1.1, label the carapace on the blue crab. [1] (ii) State two other features of a typical adult crustacean. 1 … … 2 … … [2] (iii) Fig. 1.2 shows the right claw of the blue crab. Fig. 1.2 Make a large drawing of the crab claw shown in Fig. 1.2. Do not include markings. [4] (b) Blue crabs are harvested by humans in Chesapeake Bay, USA. A scientist used the Lincoln index to estimate the population of blue crabs in one area of Chesapeake Bay. The scientist collected the data shown in Table 1.1. Table 1.1 data collected number blue crabs captured in first sample (n1) 147 blue crabs (both marked and unmarked) captured in 139 second sample (n2) blue crabs (marked) recaptured in second sample (m2) 45 The equation for the Lincoln index is: n1 × n2 N = m2 where, N = estimate of population size n1 = number of individuals captured in first sample n2 = number of individuals (both marked and unmarked) captured in second sample m2 = number of marked individuals recaptured in second sample. (i) Use the data in Table 1.1 and the equation to estimate the population of blue crabs in the area surveyed. Give your answer to three significant figures. Space for working. … [3] (ii) State two limitations of using the mark-release-recapture method to estimate the blue crab population. 1 … … 2 … … [2] (c) Since 1990, scientists have used the mark-release-recapture method and the Lincoln index to monitor the blue crab population in Chesapeake Bay. In 2008, new rules were introduced to limit the harvesting of blue crabs. Fig. 1.3 shows the estimated population of blue crabs in Chesapeake Bay from 1990 to 2020. 300 280 260 240 220 200 180 160 population / millions 140 120 100 80 60 40 20 0 1990 1995 2000 2005 2010 2015 2020 years Fig. 1.3 Use Fig. 1.3 to evaluate the effect of the new harvesting rules on the population of blue crabs. … … … … … … … … [4] [Total: 16]

16 marks

Mark scheme: Question Answer Marks 1(a)(i) 1 carapace ; 1(a)(ii) any two from: 2 segmented, abdomen / body ; jointed legs ; two pairs of antennae ; AVP ; 1(a)(iii) outline: unbroken pencil lines and no shading ; 4 size: most of the space provided and at least as big as original picture ; in proportion ; detail any number of nodules in the pincers AND 3 spines on top edge ; 1(b)(i) (147  139) / 45 ; 3 = 454.067 ; 454 ; 1(b)(ii) any two from: 2 idea of reproduction or death of individuals ; idea of migration in to or out from area ; marked individuals are not randomly distributed ; sample size may be too small ; AVP ; 1(c) any four from: MAX 3 marks for supports and 1 from the ‘however’ 4 supports idea (MAX 3 marks) 1 positive impact on the population / increased numbers (from 2008 / 2009) ; 2 the increase was sudden / significant / large / alot (for following 2 years) ; 3 increase n population, in most years / overall, compared to 2008 ; 4 higher mean 2008–2020 compared to 1990–2007 ; 5 (one or two) highest peak(s) (in 2010 and 2017) post 2008 higher than previous peaks ; however 6 some years post-2008 had very low population / accept a specific year ; 7 other factors may be having more impact on population size ; 8 manipulation of data ;

This question in 9693/21 May/June 2025

2 Fig. 2.1 shows a great white shark, Carcharodon carcharias. Fig. 2.1 (a) (i) On Fig. 2.1 label the following features: • gill slits • caudal fin • pectoral fin. [2] (ii) State the genus for the great white shark. … [1] (b) Fig. 2.2 shows five other species of shark. species A species B species C species D species E NOT TO SCALE Fig. 2.2 Use the key to identify the binomial name of species A. 1 Dark coloured upper body go to 2 Light coloured upper body go to 3 2 Tail similar length to body length Alopias vulpinus Tail shorter than body length go to 4 3 T-shaped head Sphyrna mokarran Pointed head Galeocerdo cuvier 4 Light-coloured spots on dark stripes on upper body Rhincodon typus No light-coloured spots Carcharhinus leucas Binomial name of species A is … [1] (c) A scientist studied sharks accidentally caught from commercial fishing. The sharks were analysed to identify parasites living both internally and externally. (i) Suggest why scientists used sharks that had already been accidentally caught instead of hunting sharks especially for their research. … … … … [2] (ii) Suggest advantages and disadvantages to shark parasites of living internally instead of living externally. advantages … … … … disadvantages … … … … [4] (iii) Some parasites of sharks are crustaceans. State two features of a typical adult crustacean. 1 … 2 … [2] (d) Scientists analysed the data from two different species of shark to compare the biodiversity of the parasites living in each species. Simpson’s index of diversity was used to calculate the species diversity of parasites in the two different species of shark, F and G. The equation used to calculate Simpson’s index of diversity is shown. n 2 D = 1 – 1Σ 1 N2 2 Where: D = Simpson’s index of diversity Σ = sum of (total) n = number of individuals of each different species N = the total number of individuals of all the species. Table 2.1 shows the data calculated from the two types of shark. Table 2.1 shark species F shark species G parasite 2 2 n n n n n n N 1 N2 N 1 N2 H. tergestinus 3 0.188 0.035 12 0.162 0.026 S. viridis 2 0.125 0.016 0 0.000 0.000 A. physeteris 0 0.000 0.000 43 … … L. galei 7 0.438 0.191 17 0.230 0.053 D. betencourti 4 0.250 0.063 2 0.027 0.001 N 16 74 Σ 0.305 Σ … (i) Complete Table 2.1 for shark species G using the data provided. Give your answers to three significant figures. [4] (ii) Calculate Simpson’s index of diversity for the parasites in shark species F and G. Space for working. shark species F: … shark species G: … [1] (iii) Use the Simpson’s index of diversity values you have calculated in 2(d)(ii) to compare the relative biodiversity of parasites in the two species of shark. … … [1] [Total: 18]

18 marks

Mark scheme: 2(a)(i) 2 gill slits caudal fin pectoral (fin) 2(a)(ii) Carcharodon ; 1 2(b) Rhincodon typus ; 1 2(c)(i) idea that the sharks need to be killed to identify parasites inside ; 2 idea that these sharks have already died (as a result of being caught accidentally) / no need to deliberately kill sharks to carry out the research ; 2(c)(ii) advantages: 4 more difficult to be removed from the shark ORA ; more difficult to be removed by other organisms (e.g. cleaner fish) ORA ; protected habitat / environment for parasite to reproduce ORA ; easier access to (high value) nutrient sources e.g. blood ORA ; disadvantages: more difficult for parasite to get inside the body / more difficult for parasite to find a new host ORA ; idea that the parasite needs to evade shark’s internal body defences / immune system ORA ; hard to find a mate / isolated population / reduces genetic variation ORA ; 2(c)(iii) any two from: 2 segmented, abdomen / body ; jointed legs ; two pairs of antennae ; carapace ; 2(d)(i) 4 shark type G n n 2  n  N    N  43 0.581 ; 0.338 ; 74  0.418 ; all three values correct to 3 sig. figs ; 2(d)(ii) shark species F: 0.695 AND shark species G: 0.582 ; 1 2(d)(iii) (shark) species F has a, higher / more, biodiversity (of parasites) (as shark species F has a higher Simpson’s value) ORA ; 1

This question in 9693/22 May/June 2025

2 Fig. 2.1 shows a great white shark, Carcharodon carcharias. Fig. 2.1 (a) (i) On Fig. 2.1 label the following features: • gill slits • caudal fin • pectoral fin. [2] (ii) State the genus for the great white shark. … [1] (b) Fig. 2.2 shows five other species of shark. species A species B species C species D species E NOT TO SCALE Fig. 2.2 Use the key to identify the binomial name of species A. 1 Dark coloured upper body go to 2 Light coloured upper body go to 3 2 Tail similar length to body length Alopias vulpinus Tail shorter than body length go to 4 3 T-shaped head Sphyrna mokarran Pointed head Galeocerdo cuvier 4 Light-coloured spots on dark stripes on upper body Rhincodon typus No light-coloured spots Carcharhinus leucas Binomial name of species A is … [1] (c) A scientist studied sharks accidentally caught from commercial fishing. The sharks were analysed to identify parasites living both internally and externally. (i) Suggest why scientists used sharks that had already been accidentally caught instead of hunting sharks especially for their research. … … … … [2] (ii) Suggest advantages and disadvantages to shark parasites of living internally instead of living externally. advantages … … … … disadvantages … … … … [4] (iii) Some parasites of sharks are crustaceans. State two features of a typical adult crustacean. 1 … 2 … [2] (d) Scientists analysed the data from two different species of shark to compare the biodiversity of the parasites living in each species. Simpson’s index of diversity was used to calculate the species diversity of parasites in the two different species of shark, F and G. The equation used to calculate Simpson’s index of diversity is shown. n 2 D = 1 – 1Σ 1 N2 2 Where: D = Simpson’s index of diversity Σ = sum of (total) n = number of individuals of each different species N = the total number of individuals of all the species. Table 2.1 shows the data calculated from the two types of shark. Table 2.1 shark species F shark species G parasite 2 2 n n n n n n N 1 N2 N 1 N2 H. tergestinus 3 0.188 0.035 12 0.162 0.026 S. viridis 2 0.125 0.016 0 0.000 0.000 A. physeteris 0 0.000 0.000 43 … … L. galei 7 0.438 0.191 17 0.230 0.053 D. betencourti 4 0.250 0.063 2 0.027 0.001 N 16 74 Σ 0.305 Σ … (i) Complete Table 2.1 for shark species G using the data provided. Give your answers to three significant figures. [4] (ii) Calculate Simpson’s index of diversity for the parasites in shark species F and G. Space for working. shark species F: … shark species G: … [1] (iii) Use the Simpson’s index of diversity values you have calculated in 2(d)(ii) to compare the relative biodiversity of parasites in the two species of shark. … … [1] [Total: 18]

18 marks

Mark scheme: 2(a)(i) 2 gill slits caudal fin pectoral (fin) 2(a)(ii) Carcharodon ; 1 2(b) Rhincodon typus ; 1 2(c)(i) idea that the sharks need to be killed to identify parasites inside ; 2 idea that these sharks have already died (as a result of being caught accidentally) / no need to deliberately kill sharks to carry out the research ; 2(c)(ii) advantages: 4 more difficult to be removed from the shark ORA ; more difficult to be removed by other organisms (e.g. cleaner fish) ORA ; protected habitat / environment for parasite to reproduce ORA ; easier access to (high value) nutrient sources e.g. blood ORA ; disadvantages: more difficult for parasite to get inside the body / more difficult for parasite to find a new host ORA ; idea that the parasite needs to evade shark’s internal body defences / immune system ORA ; hard to find a mate / isolated population / reduces genetic variation ORA ; 2(c)(iii) any two from: 2 segmented, abdomen / body ; jointed legs ; two pairs of antennae ; carapace ; 2(d)(i) 4 shark type G n n 2  n  N    N  43 0.581 ; 0.338 ; 74  0.418 ; all three values correct to 3 sig. figs ; 2(d)(ii) shark species F: 0.695 AND shark species G: 0.582 ; 1 2(d)(iii) (shark) species F has a, higher / more, biodiversity (of parasites) (as shark species F has a higher Simpson’s value) ORA ; 1

This question in 9693/23 May/June 2025

4 Scientists investigated the effect of marine protected areas (MPAs) on a species of fish which feeds on seagrass. They investigated similar habitats in three areas (A, B and C) outside an MPA and three areas (D, E and F) inside an MPA. The fish were observed for the same length of time at each site. The scientists recorded: • the number of bites observed per minute per fish • the surface area of seagrass eaten by the fish. Fig. 4.1 shows the results. 25 20 number of 15 bites observed per minute per fish 10 5 0 A B C D E F outside MPA inside MPA site 35 30 25 surface area 20 of seagrass eaten by fish 15 / cm2 min-1 10 5 0 A B C D E F outside MPA inside MPA site Fig. 4.1 (a) Use the data shown in Fig. 4.1 to describe the results in both graphs. … … … … … … [3] (b) Fig. 4.2 shows the number of fish and mean length of the fish in each area. 45 40 35 30 number of 25 fish 20 15 10 5 0 A B C D E F outside MPA inside MPA site 45 40 35 30 mean 25 length of the fish 20 / cm 15 10 5 0 A B C D E F outside MPA inside MPA site Fig. 4.2 Use both graphs in Fig. 4.2 to describe the impact of the MPA on the total biomass of fish. … … … … … … [4] (c) Fig. 4.3 shows the behaviour of the fish at the six sites. 100 Key 90 swimming 80 feeding on algae 70 feeding on seagrass 60 percentage of time spent 50 per behaviour 40 30 20 10 0 A B C D E F outside MPA inside MPA site Fig. 4.3 Use the information in Fig. 4.3 to describe the behaviour of the fish outside the MPA compared to the behaviour of the fish inside the MPA. … … … … … … [3] (d) Use the information provided throughout Question 4 to explain the difference in the growth of the fish outside the MPA compared to the growth of the fish inside the MPA. … … … … … [2] [Total: 12]

12 marks

Mark scheme: 4(a) 1 fish inside the MPA take fewer bites (per minute) ORA ; 3 2 fish inside the MPA eat a greater area of seagrass (per minute) ORA ; plus any one from: 3 idea of rate of seagrass (blades) eaten inside area is approximately double compared to outside MPA ORA; 4 not a / less, significant difference in bites (per minute) inside MPA ORA ; 5 other data manipulation ; 6 AVP ; 4(b) any four from: 4 1 biomass estimated from, number of fish + (mean) length, of fish ; 2 mean length of fish is greater in MPA ORA ; 3 number of fish in MPA is (significantly) greater ORA ; 4 (therefore) total biomass is (significantly) greater in MPA ORA ; 5 reference to consistent / similar results in each area inside MPA compared to outside the MPA ; 6 appropriate comparison of data ; 4(c) fish inside the MPA, don’t feed on algae / only feed on seagrass ORA ; 3 fish inside the MPA spend longer feeding on seagrass ORA ; fish inside the MPA spend less time swimming (using energy) ORA ; 4(d) any two from: 2 1 fish outside the MPA use more energy biting (as they take more bites) / ORA ; 2 fish outside the MPA eat a smaller surface area of seagrass / ORA ; 3 fish outside the MPA get less energy (from eating seagrass) / ORA ; 4 fish outside the MPA use more energy swimming / ORA ; 5 fish outside the MPA have a lower growth rate / ORA ; 6 AVP ;

This question in 9693/21 Oct/Nov 2025