Key groups of marine organisms — Paper 2 · A Level Marine Science 9693

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

2 Fig. 2.1 shows a high magnification image of a diatom. pores Fig. 2.1 (a) Make a large drawing of the diatom shown in Fig. 2.1. Include features, but do not include the pores. Do not label the drawing. [4] (b) Diatoms are a possible source of biofuel. Diatoms absorb carbon dioxide from the atmosphere for photosynthesis. With suitable growing conditions and nutrient availability diatoms produce large amounts of lipids. Lipids can form up to 75–80% of their mass. The biomass of a population of diatoms can double in a few hours. Lipids can be removed and turned into biofuel to be used in place of fossil fuels such as oil, coal and natural gas. Diatoms require silicates as an essential nutrient to make parts of their cells. Some land plants also use silicates to make their cells. Other land plants use cellulose to make their cells. Land plants that need silicates only use 8% of the energy to make their cells compared to plants that use cellulose. Scientists believe diatoms may have similar energy requirements to land plants that use silicates. (i) State the word equation for photosynthesis. … … [2] (ii) Describe the chemical structure of lipids. … … … … [2] (iii) Suggest two ways that silicates are replenished into surface waters. 1 … … 2 … … [2] (iv) Evaluate the statement: Scientists believe diatoms may have similar energy requirements to land plants that use silicates. … … … … [2] (v) State two services that diatoms provide to the environment. 1 … 2 … [2] (c) Fig. 2.2 shows a food web containing diatoms. shark 19.0 a.u. tuna 201 a.u. herring anchovy 2110 a.u. crab larvae copepods fish larvae (zooplankton) 19 900 a.u. diatoms 136 000 a.u. Fig. 2.2 (i) State the name of a tertiary consumer found in Fig. 2.2. … [1] (ii) The energy held in each trophic level for one food chain is shown in arbitrary units (a.u.) in the food web. Construct a pyramid of energy for this food chain. Label the pyramid of energy. [3] (iii) The energy transfer efficiency is the percentage of energy held in one trophic level that is passed onto the next. Calculate the energy transfer efficiency from diatoms to fish larvae. Give your answer to an appropriate number of significant figures. Show your working. … % [3] (iv) The energy transfer efficiency from tuna to shark is 9.45%. Explain reasons why the energy transfer efficiency calculated in (c)(iii) differs from the energy transfer efficiency from tuna to shark. … … … … … … [3] (v) Suggest the impact on the pyramid of energy from (c)(ii) if the quantity of silicates in the ocean is reduced. … … [1] [Total: 25]

25 marks

Mark scheme: 2(a) outline is an oval shape (single unbroken line, no sketchy lines) ; 4 size (larger than the diagram) ; detail (central groove running lengthwise, with break in the middle, 2 rows white spots, two outer rows of white structures evenly distributed with clear gap to outer edge of diatom) ; proportions of their included details (relative sizes of groove, spots and / two outer rows of white structures) ; 2(b)(i) carbon dioxide + water ; 2 → glucose + oxygen ; 2(b)(ii) any 2 from: 2 all contain carbon / C + oxygen / O + hydrogen / H ; (many are formed from) fatty acids and glycerol ; AVP ;; 2(b)(iii) any 2 from: 2 decomposition / decay ; upwelling ; run-off ; 2(b)(iv) any 2 from: 2 both types of organisms have silica parts (of cell), so may be justified in statement ; no scientific data / investigations to support this ; land and sea organisms may be from different kingdoms / phyla / domains ; different habitats / temperature differences ; (link to MP3 or 4) so energy requirements may differ ; 2(b)(v) any 2 from: 2 absorb carbon dioxide ; climate control ; release oxygen ; maintain stable, ecosystems / food web ; provide food source ; 2(c)(i) tuna OR shark ; 1 2(c)(ii) 5 rectangular closed bars ; 3 correct relative proportions from base to top + approx. the same height ; correctly labelled with named organisms from food chain ; 2(c)(iii) 19 900 3  100 ; 136 000 14.6 OR 14.63 ;; 2(c)(iv) any 3 from: 3 diatoms to fish larvae more efficient / ORA ; sharks are, more active / faster / longer distance, swimmers than fish larvae / ORA ; (which) increases energy use ; (lost) through heat / movement / respiration ; (lost) through egestion / parts uneaten or undigested ; 2(c)(v) any 1 from: 1 all boxes would (eventually) reduce in size ; size of diatom box would reduce first ;

This question in 9693/21 Oct/Nov 2022

4 Skate are cartilaginous fish which live in the benthic zone. (a) (i) State two ways that cartilaginous fish differ from bony fish. 1 … 2 … [2] (ii) State the location of the benthic zone. … [1] (b) Fig. 4.1 shows some anatomy of a skate fish. snout eye pectoral fin tail Fig. 4.1 Fig. 4.2 shows five species of skate, A, B, C, D and E. A B C D E NOT TO SCALE Fig. 4.2 Use the key to identify the binomial name of species C. 1 Sharp snout … go to 2 Rounded snout … go to 3 2 One large spot on each pectoral fin … Beringraja binoculata Even-sized small spots all over the body … Dipturus laevis 3 A row of thorns from the head down the body … Amblyraja radiata No thorns on the body … go to 4 4 Tail longer than the body … Fenestraja ishiyamai Tail shorter than the body … Dipturus chinensis Binomial name of species C is … [1] (c) Suggest two adaptations skate have to living in the benthic zone. 1 … … 2 … … [2] [Total: 6]

6 marks

Mark scheme: 4(a)(i) any 2 from: 2 cartilaginous / non-ossified skeleton ; gill slits / no operculum ; denticles ; no swim bladder ; lateral line is not visible ; 4(a)(ii) (just above) ocean floor / AW ; 1 4(b) Amblyraja radiata ; 1 4(c) any 2 from: 2 camouflaged (with the benthic zone) / OWTTE ; (dorso-ventrally) flattened ; protruding eyes / eyes on top of the head / eyes found dorsally ; ability to bury in sand ; mouth on underside – for (benthic) feeding ; AVP ;

This question in 9693/21 Oct/Nov 2022

2 Fig. 2.1 shows a high magnification image of a diatom. pores Fig. 2.1 (a) Make a large drawing of the diatom shown in Fig. 2.1. Include features, but do not include the pores. Do not label the drawing. [4] (b) Diatoms are a possible source of biofuel. Diatoms absorb carbon dioxide from the atmosphere for photosynthesis. With suitable growing conditions and nutrient availability diatoms produce large amounts of lipids. Lipids can form up to 75–80% of their mass. The biomass of a population of diatoms can double in a few hours. Lipids can be removed and turned into biofuel to be used in place of fossil fuels such as oil, coal and natural gas. Diatoms require silicates as an essential nutrient to make parts of their cells. Some land plants also use silicates to make their cells. Other land plants use cellulose to make their cells. Land plants that need silicates only use 8% of the energy to make their cells compared to plants that use cellulose. Scientists believe diatoms may have similar energy requirements to land plants that use silicates. (i) State the word equation for photosynthesis. … … [2] (ii) Describe the chemical structure of lipids. … … … … [2] (iii) Suggest two ways that silicates are replenished into surface waters. 1 … … 2 … … [2] (iv) Evaluate the statement: Scientists believe diatoms may have similar energy requirements to land plants that use silicates. … … … … [2] (v) State two services that diatoms provide to the environment. 1 … 2 … [2] (c) Fig. 2.2 shows a food web containing diatoms. shark 19.0 a.u. tuna 201 a.u. herring anchovy 2110 a.u. crab larvae copepods fish larvae (zooplankton) 19 900 a.u. diatoms 136 000 a.u. Fig. 2.2 (i) State the name of a tertiary consumer found in Fig. 2.2. … [1] (ii) The energy held in each trophic level for one food chain is shown in arbitrary units (a.u.) in the food web. Construct a pyramid of energy for this food chain. Label the pyramid of energy. [3] (iii) The energy transfer efficiency is the percentage of energy held in one trophic level that is passed onto the next. Calculate the energy transfer efficiency from diatoms to fish larvae. Give your answer to an appropriate number of significant figures. Show your working. … % [3] (iv) The energy transfer efficiency from tuna to shark is 9.45%. Explain reasons why the energy transfer efficiency calculated in (c)(iii) differs from the energy transfer efficiency from tuna to shark. … … … … … … [3] (v) Suggest the impact on the pyramid of energy from (c)(ii) if the quantity of silicates in the ocean is reduced. … … [1] [Total: 25]

25 marks

Mark scheme: 2(a) outline is an oval shape (single unbroken line, no sketchy lines) ; 4 size (larger than the diagram) ; detail (central groove running lengthwise, with break in the middle, 2 rows white spots, two outer rows of white structures evenly distributed with clear gap to outer edge of diatom) ; proportions of their included details (relative sizes of groove, spots and / two outer rows of white structures) ; 2(b)(i) carbon dioxide + water ; 2 → glucose + oxygen ; 2(b)(ii) any 2 from: 2 all contain carbon / C + oxygen / O + hydrogen / H ; (many are formed from) fatty acids and glycerol ; AVP ;; 2(b)(iii) any 2 from: 2 decomposition / decay ; upwelling ; run-off ; 2(b)(iv) any 2 from: 2 both types of organisms have silica parts (of cell), so may be justified in statement ; no scientific data / investigations to support this ; land and sea organisms may be from different kingdoms / phyla / domains ; different habitats / temperature differences ; (link to MP3 or 4) so energy requirements may differ ; 2(b)(v) any 2 from: 2 absorb carbon dioxide ; climate control ; release oxygen ; maintain stable, ecosystems / food web ; provide food source ; 2(c)(i) tuna OR shark ; 1 2(c)(ii) 5 rectangular closed bars ; 3 correct relative proportions from base to top + approx. the same height ; correctly labelled with named organisms from food chain ; 2(c)(iii) 19 900 3  100 ; 136 000 14.6 OR 14.63 ;; 2(c)(iv) any 3 from: 3 diatoms to fish larvae more efficient / ORA ; sharks are, more active / faster / longer distance, swimmers than fish larvae / ORA ; (which) increases energy use ; (lost) through heat / movement / respiration ; (lost) through egestion / parts uneaten or undigested ; 2(c)(v) any 1 from: 1 all boxes would (eventually) reduce in size ; size of diatom box would reduce first ;

This question in 9693/22 Oct/Nov 2022

4 Skate are cartilaginous fish which live in the benthic zone. (a) (i) State two ways that cartilaginous fish differ from bony fish. 1 … 2 … [2] (ii) State the location of the benthic zone. … [1] (b) Fig. 4.1 shows some anatomy of a skate fish. snout eye pectoral fin tail Fig. 4.1 Fig. 4.2 shows five species of skate, A, B, C, D and E. A B C D E NOT TO SCALE Fig. 4.2 Use the key to identify the binomial name of species C. 1 Sharp snout … go to 2 Rounded snout … go to 3 2 One large spot on each pectoral fin … Beringraja binoculata Even-sized small spots all over the body … Dipturus laevis 3 A row of thorns from the head down the body … Amblyraja radiata No thorns on the body … go to 4 4 Tail longer than the body … Fenestraja ishiyamai Tail shorter than the body … Dipturus chinensis Binomial name of species C is … [1] (c) Suggest two adaptations skate have to living in the benthic zone. 1 … … 2 … … [2] [Total: 6]

6 marks

Mark scheme: 4(a)(i) any 2 from: 2 cartilaginous / non-ossified skeleton ; gill slits / no operculum ; denticles ; no swim bladder ; lateral line is not visible ; 4(a)(ii) (just above) ocean floor / AW ; 1 4(b) Amblyraja radiata ; 1 4(c) any 2 from: 2 camouflaged (with the benthic zone) / OWTTE ; (dorso-ventrally) flattened ; protruding eyes / eyes on top of the head / eyes found dorsally ; ability to bury in sand ; mouth on underside – for (benthic) feeding ; AVP ;

This question in 9693/22 Oct/Nov 2022

2 Fig. 2.1 shows a high magnification image of a diatom. pores Fig. 2.1 (a) Make a large drawing of the diatom shown in Fig. 2.1. Include features, but do not include the pores. Do not label the drawing. [4] (b) Diatoms are a possible source of biofuel. Diatoms absorb carbon dioxide from the atmosphere for photosynthesis. With suitable growing conditions and nutrient availability diatoms produce large amounts of lipids. Lipids can form up to 75–80% of their mass. The biomass of a population of diatoms can double in a few hours. Lipids can be removed and turned into biofuel to be used in place of fossil fuels such as oil, coal and natural gas. Diatoms require silicates as an essential nutrient to make parts of their cells. Some land plants also use silicates to make their cells. Other land plants use cellulose to make their cells. Land plants that need silicates only use 8% of the energy to make their cells compared to plants that use cellulose. Scientists believe diatoms may have similar energy requirements to land plants that use silicates. (i) State the word equation for photosynthesis. … … [2] (ii) Describe the chemical structure of lipids. … … … … [2] (iii) Suggest two ways that silicates are replenished into surface waters. 1 … … 2 … … [2] (iv) Evaluate the statement: Scientists believe diatoms may have similar energy requirements to land plants that use silicates. … … … … [2] (v) State two services that diatoms provide to the environment. 1 … 2 … [2] (c) Fig. 2.2 shows a food web containing diatoms. shark 19.0 a.u. tuna 201 a.u. herring anchovy 2110 a.u. crab larvae copepods fish larvae (zooplankton) 19 900 a.u. diatoms 136 000 a.u. Fig. 2.2 (i) State the name of a tertiary consumer found in Fig. 2.2. … [1] (ii) The energy held in each trophic level for one food chain is shown in arbitrary units (a.u.) in the food web. Construct a pyramid of energy for this food chain. Label the pyramid of energy. [3] (iii) The energy transfer efficiency is the percentage of energy held in one trophic level that is passed onto the next. Calculate the energy transfer efficiency from diatoms to fish larvae. Give your answer to an appropriate number of significant figures. Show your working. … % [3] (iv) The energy transfer efficiency from tuna to shark is 9.45%. Explain reasons why the energy transfer efficiency calculated in (c)(iii) differs from the energy transfer efficiency from tuna to shark. … … … … … … [3] (v) Suggest the impact on the pyramid of energy from (c)(ii) if the quantity of silicates in the ocean is reduced. … … [1] [Total: 25]

25 marks

Mark scheme: 2(a) outline is an oval shape (single unbroken line, no sketchy lines) ; 4 size (larger than the diagram) ; detail (central groove running lengthwise, with break in the middle, 2 rows white spots, two outer rows of white structures evenly distributed with clear gap to outer edge of diatom) ; proportions of their included details (relative sizes of groove, spots and / two outer rows of white structures) ; 2(b)(i) carbon dioxide + water ; 2 → glucose + oxygen ; 2(b)(ii) any 2 from: 2 all contain carbon / C + oxygen / O + hydrogen / H ; (many are formed from) fatty acids and glycerol ; AVP ;; 2(b)(iii) any 2 from: 2 decomposition / decay ; upwelling ; run-off ; 2(b)(iv) any 2 from: 2 both types of organisms have silica parts (of cell), so may be justified in statement ; no scientific data / investigations to support this ; land and sea organisms may be from different kingdoms / phyla / domains ; different habitats / temperature differences ; (link to MP3 or 4) so energy requirements may differ ; 2(b)(v) any 2 from: 2 absorb carbon dioxide ; climate control ; release oxygen ; maintain stable, ecosystems / food web ; provide food source ; 2(c)(i) tuna OR shark ; 1 2(c)(ii) 5 rectangular closed bars ; 3 correct relative proportions from base to top + approx. the same height ; correctly labelled with named organisms from food chain ; 2(c)(iii) 19 900 3  100 ; 136 000 14.6 OR 14.63 ;; 2(c)(iv) any 3 from: 3 diatoms to fish larvae more efficient / ORA ; sharks are, more active / faster / longer distance, swimmers than fish larvae / ORA ; (which) increases energy use ; (lost) through heat / movement / respiration ; (lost) through egestion / parts uneaten or undigested ; 2(c)(v) any 1 from: 1 all boxes would (eventually) reduce in size ; size of diatom box would reduce first ;

This question in 9693/23 Oct/Nov 2022

4 Skate are cartilaginous fish which live in the benthic zone. (a) (i) State two ways that cartilaginous fish differ from bony fish. 1 … 2 … [2] (ii) State the location of the benthic zone. … [1] (b) Fig. 4.1 shows some anatomy of a skate fish. snout eye pectoral fin tail Fig. 4.1 Fig. 4.2 shows five species of skate, A, B, C, D and E. A B C D E NOT TO SCALE Fig. 4.2 Use the key to identify the binomial name of species C. 1 Sharp snout … go to 2 Rounded snout … go to 3 2 One large spot on each pectoral fin … Beringraja binoculata Even-sized small spots all over the body … Dipturus laevis 3 A row of thorns from the head down the body … Amblyraja radiata No thorns on the body … go to 4 4 Tail longer than the body … Fenestraja ishiyamai Tail shorter than the body … Dipturus chinensis Binomial name of species C is … [1] (c) Suggest two adaptations skate have to living in the benthic zone. 1 … … 2 … … [2] [Total: 6]

6 marks

Mark scheme: 4(a)(i) any 2 from: 2 cartilaginous / non-ossified skeleton ; gill slits / no operculum ; denticles ; no swim bladder ; lateral line is not visible ; 4(a)(ii) (just above) ocean floor / AW ; 1 4(b) Amblyraja radiata ; 1 4(c) any 2 from: 2 camouflaged (with the benthic zone) / OWTTE ; (dorso-ventrally) flattened ; protruding eyes / eyes on top of the head / eyes found dorsally ; ability to bury in sand ; mouth on underside – for (benthic) feeding ; AVP ;

This question in 9693/23 Oct/Nov 2022

5 Fig. 5.1 shows a blue shark. Fig. 5.1 (a) Make a large drawing of part of the blue shark shown in the box in Fig. 5.1. Do not label your diagram. [4] (b) Blue sharks mainly inhabit the epipelagic zone. State what is meant by the epipelagic zone. … … [1] (c) Explain why blue sharks are described as carnivores and predators. … … … … [2] (d) Blue sharks have been extensively fished in many parts of the world, but little is known about their population size. Information about their population size is estimated by studying catch data from blue shark fisheries. Fig. 5.2 shows the global annual blue shark catch and the catch effort from 1980 to 2017. The catch effort is the global number of days that all boats spend fishing for blue shark. global catch effort 160 140 120 100 global global catch effort annual catch / arbitrary units 80/ 1000 tonnes 60 40 20 0 1980 1985 1990 1995 2000 2005 2010 2015 2020 year Fig. 5.2 (i) Compare the catch and catch effort trends shown in Fig. 5.2. … … … … [2] (ii) Evaluate how useful these data are for understanding the population trends of the blue shark. … … … … [2]

11 marks

Mark scheme: 5(a) clear outline ; suitable size ; in proportion ; detail ; 5(b) (upper) part of (open) ocean where light is available (for producers) ; 1 5(c) (all) carnivores eat, meat / do not eat plants / other animals / named animals / consumers ; (predators) hunt animals / prey on animals / catch animals / kill animals ; 2 5(d)(i) any 2 of; both catch effort and catch (generally) increase OR more effort was put into catching blue sharks, global catch (usually) increased ; catch effort and catch rapidly increasing from (1994–1998) onwards / idea that before (1994–1998) there was minimal change / stable ; (global annual) catch, reduces / decreases, in 2015 despite catch effort continuing to increase ; catch effort begins to increase in 1994 OR global annual catch begins to increase more in 1998 ; 2 5(d)(ii) (idea of) most of data of little use as population size unknown ; idea that decreasing catch, from 2015 / despite increased effort, suggests a, decrease in / low population ; 2 Question Answer Marks 5(d)(iii) any 2 of; chance of recapturing marked individuals very low ; due to (large) size of area that individuals exist in ; idea that it is difficult to account for births and deaths ; idea that population is not evenly distributed e.g. move in groups or schools ; 2

This question in 9693/21 May/June 2023

4 Fig. 4.1 shows a boxer crab with two anemones attached to its front claws. Fig. 4.1 (a) Boxer crabs and anemones show a mutualistic relationship. Explain why this relationship is an example of mutualism. … … … … [2] (b) Boxer crabs are crustaceans. State one main feature of a typical adult crustacean. … [1] (c) Anemones belong to the same phylum as corals. Name this phylum. … [1] (d) Scientists investigated the relationship between the boxer crabs and the anemones. They measured the size of the anemones on the left and right front claws on 30 crabs. Fig. 4.2 is a scatter diagram showing the results. 3.5 3 2.5 2 right anemone diameter / mm 1.5 1 0.5 0 0 0.5 1 1.5 2 2.5 3 3.5 left anemone diameter / mm Fig. 4.2 (i) Scientists applied Spearman’s rank correlation to the data. Explain why Spearman’s rank correlation is a suitable way to analyse these data. … … … … [2] (ii) Spearman’s rank correlation uses the following equation: 6 × !D 2 rs = 1 – ( n3 – n ) A value for !D 2 was calculated as 509.0 Complete the calculation for the rs value using the equation. Give your answer to two significant figures. Show your working. … [3] (iii) State a conclusion about the correlation between the anemone size on each claw. Use your calculated value for rs from (d)(ii) to support your answer. … … … … [2] (e) Scientists hypothesised that the boxer crabs controlled the size of the anemones on their claws. (i) Suggest a reason why the boxer crabs might need to control the size of the anemones. … … [1] The scientists investigated the growth over a period of 60 days of: • anemones that were attached to crab claws • anemones that had never been attached to crab claws • anemones that had been attached to crab claws but were removed. Fig. 4.3 shows the results. 5 Key day 1 day 30 4 day 60 mean 3 diameter of anemone / mm 2 1 0 anemones anemones never anemones removed attached to claws attached to claws from claws Fig. 4.3 (ii) Discuss whether the data in Fig. 4.3 support the idea that the crabs controlled the size of the anemones. … … … … … … [3] [Total: 15]

15 marks

Mark scheme: 4(a) both organisms benefit ; crab gets protection AND anemone gets food ; 2 4(b) carapace / segmented abdomen / jointed legs / two pairs of antennae ; 1 4(c) Cnidaria ; 1 4(d)(i) any 2 of: scattergram appears to show a (positive) correlation ; allows them to determine if there is a significant / strong correlation ; idea of using data that can be ranked ; 2 4(d)(ii) substitution of numbers into equation ; correct answer only to any number of sig. figs. From 0.8867630701 ; reasonable answer expressed to 2 significant figures ; 3 4(d)(iii) (strong) positive correlation ; as answer is close to 1 ; 2 4(e)(i) to keep anemones a manageable size ; 1 Question Answer Marks 4(e)(ii) any 3 of: supports idea as anemones removed grow at similar rate as anemones never attached ; (whereas) attached anemones change little in size ; however doesn’t prove crabs control this ; correlation is not causation / could be due to another factor (such as area available for attachment) ; idea of larger sample size would give firmer conclusion ; 3

This question in 9693/22 May/June 2023

4 Fig. 4.1 shows a boxer crab with two anemones attached to its front claws. Fig. 4.1 (a) Boxer crabs and anemones show a mutualistic relationship. Explain why this relationship is an example of mutualism. … … … … [2] (b) Boxer crabs are crustaceans. State one main feature of a typical adult crustacean. … [1] (c) Anemones belong to the same phylum as corals. Name this phylum. … [1] (d) Scientists investigated the relationship between the boxer crabs and the anemones. They measured the size of the anemones on the left and right front claws on 30 crabs. Fig. 4.2 is a scatter diagram showing the results. 3.5 3 2.5 2 right anemone diameter / mm 1.5 1 0.5 0 0 0.5 1 1.5 2 2.5 3 3.5 left anemone diameter / mm Fig. 4.2 (i) Scientists applied Spearman’s rank correlation to the data. Explain why Spearman’s rank correlation is a suitable way to analyse these data. … … … … [2] (ii) Spearman’s rank correlation uses the following equation: 6 × !D 2 rs = 1 – ( n3 – n ) A value for !D 2 was calculated as 509.0 Complete the calculation for the rs value using the equation. Give your answer to two significant figures. Show your working. … [3] (iii) State a conclusion about the correlation between the anemone size on each claw. Use your calculated value for rs from (d)(ii) to support your answer. … … … … [2] (e) Scientists hypothesised that the boxer crabs controlled the size of the anemones on their claws. (i) Suggest a reason why the boxer crabs might need to control the size of the anemones. … … [1] The scientists investigated the growth over a period of 60 days of: • anemones that were attached to crab claws • anemones that had never been attached to crab claws • anemones that had been attached to crab claws but were removed. Fig. 4.3 shows the results. 5 Key day 1 day 30 4 day 60 mean 3 diameter of anemone / mm 2 1 0 anemones anemones never anemones removed attached to claws attached to claws from claws Fig. 4.3 (ii) Discuss whether the data in Fig. 4.3 support the idea that the crabs controlled the size of the anemones. … … … … … … [3] [Total: 15]

15 marks

Mark scheme: 4(a) both organisms benefit ; crab gets protection AND anemone gets food ; 2 4(b) carapace / segmented abdomen / jointed legs / two pairs of antennae ; 1 4(c) Cnidaria ; 1 4(d)(i) any 2 of: scattergram appears to show a (positive) correlation ; allows them to determine if there is a significant / strong correlation ; idea of using data that can be ranked ; 2 4(d)(ii) substitution of numbers into equation ; correct answer only to any number of sig. figs. From 0.8867630701 ; reasonable answer expressed to 2 significant figures ; 3 4(d)(iii) (strong) positive correlation ; as answer is close to 1 ; 2 4(e)(i) to keep anemones a manageable size ; 1 Question Answer Marks 4(e)(ii) any 3 of: supports idea as anemones removed grow at similar rate as anemones never attached ; (whereas) attached anemones change little in size ; however doesn’t prove crabs control this ; correlation is not causation / could be due to another factor (such as area available for attachment) ; idea of larger sample size would give firmer conclusion ; 3

This question in 9693/23 May/June 2023

3 Fig. 3.1 shows a red snapper, a fish commonly harvested for human food from coral reefs. Fig. 3.1 (a) Make a large drawing of the red snapper in Fig. 3.1. Do not include the scales. [4] (b) On your diagram label the following features: • operculum • pectoral fin. [2] (c) (i) Describe one method that could be used to estimate the population of red snapper on a coral reef. … … … … … … … … [4] (ii) Scientists investigated the population of red snapper on a coral reef every month for six months. Draw a results table for this investigation. Include full headings in the results table, but do not write in any results. [1] (iii) State two biotic factors that affect the population of red snapper on a coral reef. 1 … 2 … [2] (d) Scientists investigated the effect of an artificial reef on the populations of six fish species. The area did not contain any natural reefs. They collected data using fish traps from an artificial reef and from an area 150 m away from the artificial reef, which had no reef. The number of fish caught in each area over 8 hours was recorded. Table 3.1 shows the results. Table 3.1 number of fish caught fish species artificial reef no reef P 2 1 Q 6 1 R 137 8 S 45 0 T 129 2 U 0 1 The scientists made the statement: ‘The artificial reef has increased the biodiversity of the area.’ (i) Discuss the extent to which the data supports this statement. … … … … … … [3] (ii) The artificial reef was built 750 m offshore. Discuss the possible effects of the artificial reef on the shore. … … … … … … [3] [Total: 19]

19 marks

Mark scheme: 3(a) outline (neat lines, no shading) ; 4 size (larger than the original) ; proportion (operculum positioned at around ⅓ of the body length (not including caudal fin) and correct body shape, pectoral fin reaching to approximately the middle of the body) ; detail (all fins included, eye, mouth, caudal peduncle) ; 3(b) 2 operculum Pectoral fin 3(c)(i) any 4 from: 4 catch (a selection of the species at the reef) AND count / stated number caught AND tag (all fish) and release ; return (stated time) later and catch a sample of the species ; count the number of fish tagged AND the total caught the second time ; apply the Lincoln index ; AVP ; 3(c)(ii) 1 Date / month Total number (of red snapper) caught Number (red snapper) tagged Number (red snapper) untagged 3(c)(iii) any 2 from: 2 competition ; disease / parasites ; predation ; AVP ; 3(d)(i) any 3 from: 3 5 species of fish / same no. of species / five out of six species / same species richness, in each area; (but there may be) other species affected they did not monitor / data not collected on, all species / species other than fish ; (on the reef area) there is a large increase in numbers, of 2 species / R and T, OR there is a small increase in, 2 species / Q and P, OR a new species / S, is attracted to artificial reef ; (but) there is a reduction in numbers of 1 species / U (in the artificial reef) / (the species that reduced / U) had only a small number of fish in the area with no reef ; no data for the areas before the reef was built ; fish may have, moved / migrated, from the area without a reef to the area of reef ; data only includes species biodiversity / data does not include genetic or environmental biodiversity ; data manipulation ; AVP ; 3(d)(ii) any 3 from: 3 reduces storm surges ; as they absorb (some of) the energy (of the waves) ; waves break before the shore ; reduces shoreline erosion ; shore profile may change / sand deposited / deeper substrate ; because currents are lower behind the reef ; protects, seagrass beds / other habitats, between reef and shore ; AVP ;

This question in 9693/21 Oct/Nov 2023

3 Fig. 3.1 shows a red snapper, a fish commonly harvested for human food from coral reefs. Fig. 3.1 (a) Make a large drawing of the red snapper in Fig. 3.1. Do not include the scales. [4] (b) On your diagram label the following features: • operculum • pectoral fin. [2] (c) (i) Describe one method that could be used to estimate the population of red snapper on a coral reef. … … … … … … … … [4] (ii) Scientists investigated the population of red snapper on a coral reef every month for six months. Draw a results table for this investigation. Include full headings in the results table, but do not write in any results. [1] (iii) State two biotic factors that affect the population of red snapper on a coral reef. 1 … 2 … [2] (d) Scientists investigated the effect of an artificial reef on the populations of six fish species. The area did not contain any natural reefs. They collected data using fish traps from an artificial reef and from an area 150 m away from the artificial reef, which had no reef. The number of fish caught in each area over 8 hours was recorded. Table 3.1 shows the results. Table 3.1 number of fish caught fish species artificial reef no reef P 2 1 Q 6 1 R 137 8 S 45 0 T 129 2 U 0 1 The scientists made the statement: ‘The artificial reef has increased the biodiversity of the area.’ (i) Discuss the extent to which the data supports this statement. … … … … … … [3] (ii) The artificial reef was built 750 m offshore. Discuss the possible effects of the artificial reef on the shore. … … … … … … [3] [Total: 19]

19 marks

Mark scheme: 3(a) outline (neat lines, no shading) ; 4 size (larger than the original) ; proportion (operculum positioned at around ⅓ of the body length (not including caudal fin) and correct body shape, pectoral fin reaching to approximately the middle of the body) ; detail (all fins included, eye, mouth, caudal peduncle) ; 3(b) 2 operculum Pectoral fin 3(c)(i) any 4 from: 4 catch (a selection of the species at the reef) AND count / stated number caught AND tag (all fish) and release ; return (stated time) later and catch a sample of the species ; count the number of fish tagged AND the total caught the second time ; apply the Lincoln index ; AVP ; 3(c)(ii) 1 Date / month Total number (of red snapper) caught Number (red snapper) tagged Number (red snapper) untagged 3(c)(iii) any 2 from: 2 competition ; disease / parasites ; predation ; AVP ; 3(d)(i) any 3 from: 3 5 species of fish / same no. of species / five out of six species / same species richness, in each area; (but there may be) other species affected they did not monitor / data not collected on, all species / species other than fish ; (on the reef area) there is a large increase in numbers, of 2 species / R and T, OR there is a small increase in, 2 species / Q and P, OR a new species / S, is attracted to artificial reef ; (but) there is a reduction in numbers of 1 species / U (in the artificial reef) / (the species that reduced / U) had only a small number of fish in the area with no reef ; no data for the areas before the reef was built ; fish may have, moved / migrated, from the area without a reef to the area of reef ; data only includes species biodiversity / data does not include genetic or environmental biodiversity ; data manipulation ; AVP ; 3(d)(ii) any 3 from: 3 reduces storm surges ; as they absorb (some of) the energy (of the waves) ; waves break before the shore ; reduces shoreline erosion ; shore profile may change / sand deposited / deeper substrate ; because currents are lower behind the reef ; protects, seagrass beds / other habitats, between reef and shore ; AVP ;

This question in 9693/22 Oct/Nov 2023

3 Fig. 3.1 shows a red snapper, a fish commonly harvested for human food from coral reefs. Fig. 3.1 (a) Make a large drawing of the red snapper in Fig. 3.1. Do not include the scales. [4] (b) On your diagram label the following features: • operculum • pectoral fin. [2] (c) (i) Describe one method that could be used to estimate the population of red snapper on a coral reef. … … … … … … … … [4] (ii) Scientists investigated the population of red snapper on a coral reef every month for six months. Draw a results table for this investigation. Include full headings in the results table, but do not write in any results. [1] (iii) State two biotic factors that affect the population of red snapper on a coral reef. 1 … 2 … [2] (d) Scientists investigated the effect of an artificial reef on the populations of six fish species. The area did not contain any natural reefs. They collected data using fish traps from an artificial reef and from an area 150 m away from the artificial reef, which had no reef. The number of fish caught in each area over 8 hours was recorded. Table 3.1 shows the results. Table 3.1 number of fish caught fish species artificial reef no reef P 2 1 Q 6 1 R 137 8 S 45 0 T 129 2 U 0 1 The scientists made the statement: ‘The artificial reef has increased the biodiversity of the area.’ (i) Discuss the extent to which the data supports this statement. … … … … … … [3] (ii) The artificial reef was built 750 m offshore. Discuss the possible effects of the artificial reef on the shore. … … … … … … [3] [Total: 19]

19 marks

Mark scheme: 3(a) outline (neat lines, no shading) ; 4 size (larger than the original) ; proportion (operculum positioned at around ⅓ of the body length (not including caudal fin) and correct body shape, pectoral fin reaching to approximately the middle of the body) ; detail (all fins included, eye, mouth, caudal peduncle) ; 3(b) 2 operculum Pectoral fin 3(c)(i) any 4 from: 4 catch (a selection of the species at the reef) AND count / stated number caught AND tag (all fish) and release ; return (stated time) later and catch a sample of the species ; count the number of fish tagged AND the total caught the second time ; apply the Lincoln index ; AVP ; 3(c)(ii) 1 Date / month Total number (of red snapper) caught Number (red snapper) tagged Number (red snapper) untagged 3(c)(iii) any 2 from: 2 competition ; disease / parasites ; predation ; AVP ; 3(d)(i) any 3 from: 3 5 species of fish / same no. of species / five out of six species / same species richness, in each area; (but there may be) other species affected they did not monitor / data not collected on, all species / species other than fish ; (on the reef area) there is a large increase in numbers, of 2 species / R and T, OR there is a small increase in, 2 species / Q and P, OR a new species / S, is attracted to artificial reef ; (but) there is a reduction in numbers of 1 species / U (in the artificial reef) / (the species that reduced / U) had only a small number of fish in the area with no reef ; no data for the areas before the reef was built ; fish may have, moved / migrated, from the area without a reef to the area of reef ; data only includes species biodiversity / data does not include genetic or environmental biodiversity ; data manipulation ; AVP ; 3(d)(ii) any 3 from: 3 reduces storm surges ; as they absorb (some of) the energy (of the waves) ; waves break before the shore ; reduces shoreline erosion ; shore profile may change / sand deposited / deeper substrate ; because currents are lower behind the reef ; protects, seagrass beds / other habitats, between reef and shore ; AVP ;

This question in 9693/23 Oct/Nov 2023

1 Zooplankton is composed of a variety of organisms, including copepods. (a) Fig. 1.1 shows a copepod found in zooplankton. Fig. 1.1 Make a large drawing of the copepod in Fig. 1.1. Do not include the internal structure of the copepod. Do not label your drawing. [4] (b) Describe the roles of zooplankton in marine ecosystems. … … … … [2] (c) Sea water samples were taken from different depths in the Arctic Ocean. Fig. 1.2 shows the percentage composition of eight species of copepod zooplankton found in the samples. Not all species occurred at each depth. Key 100 species A species B 80 species C species D 60 percentage species E composition of copepod species F zooplankton 40 species G species H 20 0 0 – 200 201 – 500 501 – 1000 sampling depth / m Fig. 1.2 (i) State how many of the eight species of copepod zooplankton are found in all three depth ranges. … [1] (ii) Use Fig. 1.2 to compare the changes in percentage composition of species A and species H. … … … … … … [3] (iii) Suggest why the percentage compositions of the copepod zooplankton species change with increasing depth. … … … … … … [3] (d) A student compared the copepod zooplankton communities by calculating the biodiversity at different depths. Table 1.1 shows the number of individuals per dm3 of sea water for the six species present at depths 0 – 200 m. Table 1.1 species of copepod zooplankton number of individuals / dm3 A 58 B 95 E 380 F 133 G 228 H 56 total number of individuals of all 950 the species (N) Simpson’s index of diversity (D) can be used to calculate biodiversity. n 2 D = 1 / N -c ` j m / = sum of (total) n = number of individuals of each different species N = the total number of individuals of all the species (i) Using the data in Table 1.1, complete Table 1.2 for species G. Table 1.2 species of copepod n / N (n / N)2 zooplankton A 0.061 0.004 B 0.100 0.010 E 0.400 0.160 F 0.140 0.020 G … … H 0.059 0.004 [1] (ii) Use Table 1.2 and the equation to calculate D for the biodiversity of copepod zooplankton between 0 – 200 m. State your answer to three significant figures. Show your working. D = … [3] (iii) The student calculated the value for D for the depth range 201 – 500 m to be 0.699. Use this value for D and your answer to (d)(ii) to describe the change in the biodiversity of copepod zooplankton as the depth increases. Justify your answer. … … … … [2] [Total: 19]

19 marks

Mark scheme: 1(a) clear outline with thin lines with no shading, no gaps ; suitable size ; in proportion ; detail ; 4 1(b) (primary / secondary) consumers / eat phytoplankton / eat plants ; provide food / make energy available / source of energy OR increase biomass, for higher trophic levels OR zooplankton are prey for / fed on by, other animals / other (marine) organisms OR source of food for other organisms ; 2 1(c)(i) 3 ; 1 1(c)(ii) any 3 from: 1 both species / A and H, have the similar (percentage) composition between 0–200 m ; 2 (percentage composition of) both species increase with depth ORA ; 3 idea of greater increase (in percentage composition) for species H ORA ; 4 ref. to greatest increase for both species between 0–200 m and 201–500 m / ORA ; 5 correct manipulation of data to support answers ; 3 Question Answer Marks 1(c)(iii) 1 idea of (presence or absence of) adaptations to different conditions e.g. different species adapted to different (environmental) conditions / some species lack adaptations to survive (and need sunlight) / composition of species H increases with depth, so H is suited to deeper areas of the ocean ; plus any 2 from: 2 (differing / changing amounts of) predation ; 3 (differing / changing) abundance of food ; 4 (differing / changing) salinity / pH ; 5 (differing / changing) oxygen (concentration) ; 6 (differing / changing) density / pressure ; 7 (differing / changing) competition ; 8 (differing / changing)(water) temperature ; 9 (differing / changing) light intensity / brightness / light penetration ; 3 1(d)(i) 0.24(0) AND 0.058 / 0.0576 ; 1 1(d)(ii)  (n / N)2 = 0.256 or 0.2556 ; 1 – 0.256 = 0.744 or 1 – 0.2556 = 0.744(4) ; calculated answer given to 3 sig figs ; 3 1(d)(iii) links change in biodiversity to change in depth e.g. biodiversity is decreasing OR the deeper, the lower biodiversity of copepod zooplankton there is OR biodiversity declines with depth ORA ; value closer to 1 indicates higher biodiversity ; 2

This question in 9693/21 May/June 2024

2 (a) Fig. 2.1 shows a plaice, Pleuronectes platessa. This is a bony fish that lives in the benthic zone. Fig. 2.1 (i) Make a large drawing of the fish in Fig. 2.1. Do not draw the markings. [4] (ii) On your drawing in (a)(i), label the following features: • lateral line • operculum • pelvic fin. [3] (iii) The larvae of plaice live in the zooplankton community. When they reach a length of 2.5 cm, they settle on the sea bed and during their development their organs migrate to one side of their body. Suggest why adult plaice do not have a swim bladder but the larvae do have a swim bladder. … … … … [2] (b) Skate are fish that also live in the benthic zone. Fig. 2.2 shows some of the anatomy of a skate. snout eye pectoral fin tail Fig. 2.2 Fig. 2.3 shows five species of skate, A, B, C, D and E. A B C D E NOT TO SCALE Fig. 2.3 Use the dichotomous key and Fig. 2.3 to identify the two species (A, B, C, D or E) that belong to the same genus. 1 Sharp snout … go to 2 Rounded snout … go to 3 2 One large spot on each pectoral fin … Beringraja binoculata Small spots all over the body … Dipturus laevis 3 A row of thorns from the head down the body … Amblyraja radiata No thorns on the body … go to 4 4 Tail longer than the body … Fenestraja ishiyamai Tail shorter than the body … Dipturus chinensis Species … and species … are from the same genus. [2] (c) Flounder are bony fish and skate are cartilaginous fish. Cartilaginous fish do not have a swim bladder, while most bony fish do have a swim bladder. State two other ways in which bony fish are different from cartilaginous fish. 1 … … 2 … … [2] [Total: 13]

13 marks

Mark scheme: 2(a)(i) clear outline with thin lines with no shading, no gaps ; suitable size ; proportion distinct ‘snout’ / caudal fin less than half, more than 1/3 body length, correct body shape ; detail (both eyes shown, delineation between body, and dorsal and anal fins) ; 4 2(a)(ii) straight line drawn (no arrowhead) touching each part ;;; 3 2(a)(iii) any 2 from: juveniles have to float to be in the zooplankton / larvae are free swimming (in the water column) ; (because) they cannot swim against a current / being buoyant reduces the energy demand for, swimming / maintaining position / keeps them closer to their, food / phytoplankton ; adults (remain on sea bed, so) do not need buoyancy ; 2 2(b) E ; B ; 2 2(c) any 2 from: (bony fish have) ossified or calcified, skeleton / (cartilaginous fish have) non-ossified / non-calcified ; (bony fish have) operculum / (cartilaginous fish have) gill slits ; (bony fish have) lack denticles OR scales (cover the body) / (cartilaginous fish have) denticles (cover the body) OR no scales ; (bony fish have) visible lateral line / (cartilaginous fish have) lateral line not visible ; 2

This question in 9693/22 May/June 2024

2 (a) Fig. 2.1 shows a plaice, Pleuronectes platessa. This is a bony fish that lives in the benthic zone. Fig. 2.1 (i) Make a large drawing of the fish in Fig. 2.1. Do not draw the markings. [4] (ii) On your drawing in (a)(i), label the following features: • lateral line • operculum • pelvic fin. [3] (iii) The larvae of plaice live in the zooplankton community. When they reach a length of 2.5 cm, they settle on the sea bed and during their development their organs migrate to one side of their body. Suggest why adult plaice do not have a swim bladder but the larvae do have a swim bladder. … … … … [2] (b) Skate are fish that also live in the benthic zone. Fig. 2.2 shows some of the anatomy of a skate. snout eye pectoral fin tail Fig. 2.2 Fig. 2.3 shows five species of skate, A, B, C, D and E. A B C D E NOT TO SCALE Fig. 2.3 Use the dichotomous key and Fig. 2.3 to identify the two species (A, B, C, D or E) that belong to the same genus. 1 Sharp snout … go to 2 Rounded snout … go to 3 2 One large spot on each pectoral fin … Beringraja binoculata Small spots all over the body … Dipturus laevis 3 A row of thorns from the head down the body … Amblyraja radiata No thorns on the body … go to 4 4 Tail longer than the body … Fenestraja ishiyamai Tail shorter than the body … Dipturus chinensis Species … and species … are from the same genus. [2] (c) Flounder are bony fish and skate are cartilaginous fish. Cartilaginous fish do not have a swim bladder, while most bony fish do have a swim bladder. State two other ways in which bony fish are different from cartilaginous fish. 1 … … 2 … … [2] [Total: 13]

13 marks

Mark scheme: 2(a)(i) clear outline with thin lines with no shading, no gaps ; suitable size ; proportion distinct ‘snout’ / caudal fin less than half, more than 1/3 body length, correct body shape ; detail (both eyes shown, delineation between body, and dorsal and anal fins) ; 4 2(a)(ii) straight line drawn (no arrowhead) touching each part ;;; 3 2(a)(iii) any 2 from: juveniles have to float to be in the zooplankton / larvae are free swimming (in the water column) ; (because) they cannot swim against a current / being buoyant reduces the energy demand for, swimming / maintaining position / keeps them closer to their, food / phytoplankton ; adults (remain on sea bed, so) do not need buoyancy ; 2 2(b) E ; B ; 2 2(c) any 2 from: (bony fish have) ossified or calcified, skeleton / (cartilaginous fish have) non-ossified / non-calcified ; (bony fish have) operculum / (cartilaginous fish have) gill slits ; (bony fish have) lack denticles OR scales (cover the body) / (cartilaginous fish have) denticles (cover the body) OR no scales ; (bony fish have) visible lateral line / (cartilaginous fish have) lateral line not visible ; 2

This question in 9693/23 May/June 2024

5 (a) Fig. 5.1 shows a brittle star which belongs to the echinoderm phylum. Fig. 5.1 Make a large drawing of the brittle star shown in Fig. 5.1. Do not include the markings on the arms. [4] (b) Sea urchins and starfish also belong to the echinoderm phylum. Fig. 5.2 shows five species of echinoderm. A B C D E Fig. 5.2 Use the key below to identify species A and B. disc-shaped body with arms … 2 1 body does not have arms … 3 body has 5 arms … Ophiura albida 2 body has 12–23 arms … Acanthaster planci body has many spines which are longer than diameter of the body … 4 3 body has many spines which are shorter than diameter of the body … Mespilia globulus spines are thin and dark in colour … Diadema setosum 4 spines are thick and light in colour … Echinometra mathaei species A: … species B: … [2] (c) Collector urchins feed on seagrass and macroalgae. Collector urchins are prey for octopus. Pufferfish consume collector urchins. Tiger sharks are predators of octopus and pufferfish. Draw a food web for the organisms described above. [2] (d) Collector urchins are often seen coated with debris such as gravel. Suggest why this may be an advantage to their survival. … … … … [2] [Total: 10]

10 marks

Mark scheme: 5(a) quality of outline (thin and continuous) in pencil ; 4 suitable size (at least as large as the photo) ; proportion (angles, length of arms, centre diameter) ; detail (minimum 2 out of the 3 curls on end of 3 arms circled) ; 5(b) Species A: Acanthaster planci ; 2 Species B: Diadema setosum ; 5(c) either: 2 for all six organisms correctly linked with 6 arrows in right direction ;; OR: food web of six organisms correct organisms with 6 lines / incorrect direction of arrows ; OR: food web of five correct organisms with correct direction of arrows ; OR: food web of six organisms correct organisms with correct direction of five arrows ; 5(d) idea of camouflage from / less likely to be seen ; 2 (so less likely to be seen / eaten) by predators / octopus / puffer fish ;

This question in 9693/21 Oct/Nov 2024

6 A survey was carried out to estimate the total population of the shark Carcharias taurus in the coastal waters off south-east Australia. Scientists attached numbered tags to a dorsal fin of the sharks. (a) Label one dorsal fin on the diagram of a Carcharias taurus in Fig. 6.1. Fig. 6.1 [1] (b) Carcharias taurus are cartilaginous fish. State two features of cartilaginous fish that are not features of bony fish. 1 … … 2 … … [2] (c) The scientists used the mark–release–recapture method to estimate the population of Carcharias taurus off the south-east coast of Australia. The data collected are shown in Table 6.1. Table 6.1 number sharks captured and marked in first sample (n1) 152 sharks captured in second sample (both marked and unmarked) (n2) 185 marked sharks recaptured in second sample (m2) 44 The equation for the Lincoln index is shown. N = n1 × n2 m2 Use the data in Table 6.1 and the equation to estimate the population of Carcharias taurus in the area surveyed. State your answer to two significant figures. Show your working. … [3] (d) Carcharias taurus is known as the grey nurse shark in Australia, the sand tiger shark in the USA and the spotted ragged-tooth shark in South Africa. Explain the importance of using the binomial system of species nomenclature. … … … … [2] (e) Scientists in the USA studied the growth rate of Carcharias taurus and found that its growth rate decreased over time as shown in Table 6.2. Table 6.2 age in years rate of growth / cm year –1 0 to 2 25 to 30 2 to 4 20 to 25 4 to 6 15 to 20 6 to 8 10 to 15 > 8 5 to 10 When a Carcharias taurus is born, it is around 1 m long. Calculate the approximate length of a 5-year-old Carcharias taurus, using the data in Table 6.2. State the units. Show your working. … [3] [Total: 11]

11 marks

Mark scheme: 6(a) correct label on one of two dorsal fins shown 1 6(b) any 2 from: 2 cartilaginous skeleton ; gill slits ; no swim bladder ; denticles ; 6(c) N = (152  185) / 44 ; 3 N = 639.090909 ; N = 640 ; 6(d) idea of consistent name used in all countries / languages ; 2 plus any 1 from: useful for comparing / sharing, scientific research ; idea it avoids confusion / problems / misunderstandings caused by using different names ; idea of useful for showing, classification / evolutionary relationships, with other organisms ; 6(e) working showing (100 cm +) appropriate gains in length ; 3 answer in range 205–230 (cm) / 2.050–2.30 (m) ; correct units for answer given ;

This question in 9693/21 Oct/Nov 2024

5 (a) Fig. 5.1 shows a brittle star which belongs to the echinoderm phylum. Fig. 5.1 Make a large drawing of the brittle star shown in Fig. 5.1. Do not include the markings on the arms. [4] (b) Sea urchins and starfish also belong to the echinoderm phylum. Fig. 5.2 shows five species of echinoderm. A B C D E Fig. 5.2 Use the key below to identify species A and B. disc-shaped body with arms … 2 1 body does not have arms … 3 body has 5 arms … Ophiura albida 2 body has 12–23 arms … Acanthaster planci body has many spines which are longer than diameter of the body … 4 3 body has many spines which are shorter than diameter of the body … Mespilia globulus spines are thin and dark in colour … Diadema setosum 4 spines are thick and light in colour … Echinometra mathaei species A: … species B: … [2] (c) Collector urchins feed on seagrass and macroalgae. Collector urchins are prey for octopus. Pufferfish consume collector urchins. Tiger sharks are predators of octopus and pufferfish. Draw a food web for the organisms described above. [2] (d) Collector urchins are often seen coated with debris such as gravel. Suggest why this may be an advantage to their survival. … … … … [2] [Total: 10]

10 marks

Mark scheme: 5(a) quality of outline (thin and continuous) in pencil ; 4 suitable size (at least as large as the photo) ; proportion (angles, length of arms, centre diameter) ; detail (minimum 2 out of the 3 curls on end of 3 arms circled) ; 5(b) Species A: Acanthaster planci ; 2 Species B: Diadema setosum ; 5(c) either: 2 for all six organisms correctly linked with 6 arrows in right direction ;; OR: food web of six organisms correct organisms with 6 lines / incorrect direction of arrows ; OR: food web of five correct organisms with correct direction of arrows ; OR: food web of six organisms correct organisms with correct direction of five arrows ; 5(d) idea of camouflage from / less likely to be seen ; 2 (so less likely to be seen / eaten) by predators / octopus / puffer fish ;

This question in 9693/22 Oct/Nov 2024

6 A survey was carried out to estimate the total population of the shark Carcharias taurus in the coastal waters off south-east Australia. Scientists attached numbered tags to a dorsal fin of the sharks. (a) Label one dorsal fin on the diagram of a Carcharias taurus in Fig. 6.1. Fig. 6.1 [1] (b) Carcharias taurus are cartilaginous fish. State two features of cartilaginous fish that are not features of bony fish. 1 … … 2 … … [2] (c) The scientists used the mark–release–recapture method to estimate the population of Carcharias taurus off the south-east coast of Australia. The data collected are shown in Table 6.1. Table 6.1 number sharks captured and marked in first sample (n1) 152 sharks captured in second sample (both marked and unmarked) (n2) 185 marked sharks recaptured in second sample (m2) 44 The equation for the Lincoln index is shown. N = n1 × n2 m2 Use the data in Table 6.1 and the equation to estimate the population of Carcharias taurus in the area surveyed. State your answer to two significant figures. Show your working. … [3] (d) Carcharias taurus is known as the grey nurse shark in Australia, the sand tiger shark in the USA and the spotted ragged-tooth shark in South Africa. Explain the importance of using the binomial system of species nomenclature. … … … … [2] (e) Scientists in the USA studied the growth rate of Carcharias taurus and found that its growth rate decreased over time as shown in Table 6.2. Table 6.2 age in years rate of growth / cm year –1 0 to 2 25 to 30 2 to 4 20 to 25 4 to 6 15 to 20 6 to 8 10 to 15 > 8 5 to 10 When a Carcharias taurus is born, it is around 1 m long. Calculate the approximate length of a 5-year-old Carcharias taurus, using the data in Table 6.2. State the units. Show your working. … [3] [Total: 11]

11 marks

Mark scheme: 6(a) correct label on one of two dorsal fins shown 1 6(b) any 2 from: 2 cartilaginous skeleton ; gill slits ; no swim bladder ; denticles ; 6(c) N = (152  185) / 44 ; 3 N = 639.090909 ; N = 640 ; 6(d) idea of consistent name used in all countries / languages ; 2 plus any 1 from: useful for comparing / sharing, scientific research ; idea it avoids confusion / problems / misunderstandings caused by using different names ; idea of useful for showing, classification / evolutionary relationships, with other organisms ; 6(e) working showing (100 cm +) appropriate gains in length ; 3 answer in range 205–230 (cm) / 2.050–2.30 (m) ; correct units for answer given ;

This question in 9693/22 Oct/Nov 2024

5 (a) Fig. 5.1 shows a brittle star which belongs to the echinoderm phylum. Fig. 5.1 Make a large drawing of the brittle star shown in Fig. 5.1. Do not include the markings on the arms. [4] (b) Sea urchins and starfish also belong to the echinoderm phylum. Fig. 5.2 shows five species of echinoderm. A B C D E Fig. 5.2 Use the key below to identify species A and B. disc-shaped body with arms … 2 1 body does not have arms … 3 body has 5 arms … Ophiura albida 2 body has 12–23 arms … Acanthaster planci body has many spines which are longer than diameter of the body … 4 3 body has many spines which are shorter than diameter of the body … Mespilia globulus spines are thin and dark in colour … Diadema setosum 4 spines are thick and light in colour … Echinometra mathaei species A: … species B: … [2] (c) Collector urchins feed on seagrass and macroalgae. Collector urchins are prey for octopus. Pufferfish consume collector urchins. Tiger sharks are predators of octopus and pufferfish. Draw a food web for the organisms described above. [2] (d) Collector urchins are often seen coated with debris such as gravel. Suggest why this may be an advantage to their survival. … … … … [2] [Total: 10]

10 marks

Mark scheme: 5(a) quality of outline (thin and continuous) in pencil ; 4 suitable size (at least as large as the photo) ; proportion (angles, length of arms, centre diameter) ; detail (minimum 2 out of the 3 curls on end of 3 arms circled) ; 5(b) Species A: Acanthaster planci ; 2 Species B: Diadema setosum ; 5(c) either: 2 for all six organisms correctly linked with 6 arrows in right direction ;; OR: food web of six organisms correct organisms with 6 lines / incorrect direction of arrows ; OR: food web of five correct organisms with correct direction of arrows ; OR: food web of six organisms correct organisms with correct direction of five arrows ; 5(d) idea of camouflage from / less likely to be seen ; 2 (so less likely to be seen / eaten) by predators / octopus / puffer fish ;

This question in 9693/23 Oct/Nov 2024

6 A survey was carried out to estimate the total population of the shark Carcharias taurus in the coastal waters off south-east Australia. Scientists attached numbered tags to a dorsal fin of the sharks. (a) Label one dorsal fin on the diagram of a Carcharias taurus in Fig. 6.1. Fig. 6.1 [1] (b) Carcharias taurus are cartilaginous fish. State two features of cartilaginous fish that are not features of bony fish. 1 … … 2 … … [2] (c) The scientists used the mark–release–recapture method to estimate the population of Carcharias taurus off the south-east coast of Australia. The data collected are shown in Table 6.1. Table 6.1 number sharks captured and marked in first sample (n1) 152 sharks captured in second sample (both marked and unmarked) (n2) 185 marked sharks recaptured in second sample (m2) 44 The equation for the Lincoln index is shown. N = n1 × n2 m2 Use the data in Table 6.1 and the equation to estimate the population of Carcharias taurus in the area surveyed. State your answer to two significant figures. Show your working. … [3] (d) Carcharias taurus is known as the grey nurse shark in Australia, the sand tiger shark in the USA and the spotted ragged-tooth shark in South Africa. Explain the importance of using the binomial system of species nomenclature. … … … … [2] (e) Scientists in the USA studied the growth rate of Carcharias taurus and found that its growth rate decreased over time as shown in Table 6.2. Table 6.2 age in years rate of growth / cm year –1 0 to 2 25 to 30 2 to 4 20 to 25 4 to 6 15 to 20 6 to 8 10 to 15 > 8 5 to 10 When a Carcharias taurus is born, it is around 1 m long. Calculate the approximate length of a 5-year-old Carcharias taurus, using the data in Table 6.2. State the units. Show your working. … [3] [Total: 11]

11 marks

Mark scheme: 6(a) correct label on one of two dorsal fins shown 1 6(b) any 2 from: 2 cartilaginous skeleton ; gill slits ; no swim bladder ; denticles ; 6(c) N = (152  185) / 44 ; 3 N = 639.090909 ; N = 640 ; 6(d) idea of consistent name used in all countries / languages ; 2 plus any 1 from: useful for comparing / sharing, scientific research ; idea it avoids confusion / problems / misunderstandings caused by using different names ; idea of useful for showing, classification / evolutionary relationships, with other organisms ; 6(e) working showing (100 cm +) appropriate gains in length ; 3 answer in range 205–230 (cm) / 2.050–2.30 (m) ; correct units for answer given ;

This question in 9693/23 Oct/Nov 2024

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

4 Fig. 4.1 shows a barrel jellyfish. Fig. 4.1 (a) Make a large drawing of the jellyfish shown in Fig. 4.1. Do not label your drawing. [4] (b) Citizen science projects encourage people to make observations in their environment and submit their observations to a research team. Scientists sometimes use citizen science projects to collect data from many people. Citizen science projects can be used to collect data on jellyfish washed up on beaches. (i) Suggest three advantages of collecting data from many people about jellyfish found on beaches instead of scientists collecting their own data. 1 … … 2 … … 3 … … [3] (ii) Suggest one disadvantage of collecting data from many people about jellyfish found on beaches instead of scientists collecting their own data. … … [1] (iii) Describe how the disadvantage you have given in 4(b)(ii) could be limited. … … [1] (iv) Jellyfish are in the phylum Cnidaria and have nematocysts. State the risk that jellyfish cause to people taking part in the study. … … [1] (v) Suggest two ways scientists can reduce the risk you have given in 4(b)(iv). 1 … … 2 … … [2] (c) Scientists investigated the relationship between nitrate ion (NO3–) and phosphate ion (PO43–) concentration in the ocean and the number of jellyfish found on beaches. (i) Explain why an increase in nitrate ion and phosphate ion concentration in the ocean can cause an increase in the jellyfish population. … … … … [2] (ii) State why the number of jellyfish found on beaches increases when the population of jellyfish increases. … … [1]

15 marks

Mark scheme: 4(a) outline: unbroken lines and no shading ; 4 size: most of the space provided and at least as big as original picture ; in proportion ; detail – bell section and three oral arms section ; 4(b)(i) any three from: 3 1 enables collection of more, data / information ; 2 (data collected from) a larger / greater, area ; 3 free / cheaper, to collect ; 4 increased awareness in conservation ; 5 idea of more effective use of scientists time ; 4(b)(ii) any one from: 1 disadvantage: 1 identification may be incorrect ; 2 could be duplication from different members of public ; 3 inaccurate estimates of numbers ; 4 variation in ease of submission due to connectivity to internet 4(b)(iii) any one from: 1 how to limit disadvantage: 1 provision of key to help public make correct identification ; ask public to provide photos so some or all of sightings can be checked 2 use of location data to identify reportings from a location (e.g. per day or week) ; 3 offer citizens training on estimating numbers ; 4 ability to save and submit reporting later ; 4(b)(iv) any one from: 1 (jellyfish) stings ; AVP ; 4(b)(v) any two from: 2 warning of risk to participants ; identification of (very) dangerous species ; advice on how to treat stings ; 4(c)(i) any two from: 2 increase in nutrients will increase productivity / rate of photosynthesis ORA ; (idea of) greater availability of food in food chains ORA ; (idea of) jellyfish are animals / consumers ; 4(c)(ii) any one from: 1 limited motility / swept in by strong currents / wave action ; competition for food / insufficient food ; the greater the population, the greater the chance of jellyfish being washed up ; 4(c)(iii) line showing similar trend to phytoplankton mass ; 2 time delay for both peaks ; 4(d)(i) increases AND decreases ; 2 peaks in 2013 ; 4(d)(ii) 300 (%) ; 1 4(d)(iii) any three from: 3 no information about nitrate and phosphate availability in graph ; idea that information is only annual / time intervals are too large ; different species peak at different times ; different species show different trends / patterns ; AVP ;

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 Fig. 4.1 shows a barrel jellyfish. Fig. 4.1 (a) Make a large drawing of the jellyfish shown in Fig. 4.1. Do not label your drawing. [4] (b) Citizen science projects encourage people to make observations in their environment and submit their observations to a research team. Scientists sometimes use citizen science projects to collect data from many people. Citizen science projects can be used to collect data on jellyfish washed up on beaches. (i) Suggest three advantages of collecting data from many people about jellyfish found on beaches instead of scientists collecting their own data. 1 … … 2 … … 3 … … [3] (ii) Suggest one disadvantage of collecting data from many people about jellyfish found on beaches instead of scientists collecting their own data. … … [1] (iii) Describe how the disadvantage you have given in 4(b)(ii) could be limited. … … [1] (iv) Jellyfish are in the phylum Cnidaria and have nematocysts. State the risk that jellyfish cause to people taking part in the study. … … [1] (v) Suggest two ways scientists can reduce the risk you have given in 4(b)(iv). 1 … … 2 … … [2] (c) Scientists investigated the relationship between nitrate ion (NO3–) and phosphate ion (PO43–) concentration in the ocean and the number of jellyfish found on beaches. (i) Explain why an increase in nitrate ion and phosphate ion concentration in the ocean can cause an increase in the jellyfish population. … … … … [2] (ii) State why the number of jellyfish found on beaches increases when the population of jellyfish increases. … … [1]

15 marks

Mark scheme: 4(a) outline: unbroken lines and no shading ; 4 size: most of the space provided and at least as big as original picture ; in proportion ; detail – bell section and three oral arms section ; 4(b)(i) any three from: 3 1 enables collection of more, data / information ; 2 (data collected from) a larger / greater, area ; 3 free / cheaper, to collect ; 4 increased awareness in conservation ; 5 idea of more effective use of scientists time ; 4(b)(ii) any one from: 1 disadvantage: 1 identification may be incorrect ; 2 could be duplication from different members of public ; 3 inaccurate estimates of numbers ; 4 variation in ease of submission due to connectivity to internet 4(b)(iii) any one from: 1 how to limit disadvantage: 1 provision of key to help public make correct identification ; ask public to provide photos so some or all of sightings can be checked 2 use of location data to identify reportings from a location (e.g. per day or week) ; 3 offer citizens training on estimating numbers ; 4 ability to save and submit reporting later ; 4(b)(iv) any one from: 1 (jellyfish) stings ; AVP ; 4(b)(v) any two from: 2 warning of risk to participants ; identification of (very) dangerous species ; advice on how to treat stings ; 4(c)(i) any two from: 2 increase in nutrients will increase productivity / rate of photosynthesis ORA ; (idea of) greater availability of food in food chains ORA ; (idea of) jellyfish are animals / consumers ; 4(c)(ii) any one from: 1 limited motility / swept in by strong currents / wave action ; competition for food / insufficient food ; the greater the population, the greater the chance of jellyfish being washed up ; 4(c)(iii) line showing similar trend to phytoplankton mass ; 2 time delay for both peaks ; 4(d)(i) increases AND decreases ; 2 peaks in 2013 ; 4(d)(ii) 300 (%) ; 1 4(d)(iii) any three from: 3 no information about nitrate and phosphate availability in graph ; idea that information is only annual / time intervals are too large ; different species peak at different times ; different species show different trends / patterns ; AVP ;

This question in 9693/23 May/June 2025

3 Organisms are classified in a taxonomic hierarchy. (a) Complete the taxonomic hierarchy to show the correct position of the levels of classification. Use the words from the box. class family genus kingdom phylum taxonomic hierarchy domain order species [1] (b) Fig. 3.1 shows a jellyfish which is in the phylum cnidaria. Fig. 3.1 Make a large drawing of the jellyfish shown in Fig. 3.1. Do not include the markings. Do not label your drawing. [4] (c) Scientists investigated the biodiversity of jellyfish in the ocean. They recorded the number of species of jellyfish found at different depths. Fig. 3.2 shows the results. number of species of jellyfish 0 10 20 30 40 50 60 0–500 501–1000 1001–1500 1501–2000 2001–2500 depth / m 2501–3000 3001–3500 3501– 4000 4001– 4500 4501–5000 Fig. 3.2 (i) Use Fig. 3.2 to describe the change in species diversity of jellyfish as depth increases. … … … … [2] (ii) Explain the distribution of jellyfish species at depths between 0 m and 1500 m of the ocean. … … … … … … [3] (iii) The thermocline in the ocean at the time the results were recorded was at a depth of approximately 30 m. Describe how a thermocline forms. … … … … [2] (iv) The scientists only counted the number of jellyfish species present. State what other measurement is needed to improve the measurement of species diversity. … … [1] (v) Species diversity is one measure of biodiversity. Describe two other levels of measuring biodiversity. … … … … … … … … [4] [Total: 17]

17 marks

Mark scheme: 3(a) 1 taxonomic hierarchy domain kingdom phylum class order family genus species 3(b) outline: unbroken lines in pencil and no shading ; 4 size: most of the space provided and at least as big as original picture ; in proportion ; detail – 3 (or 4) tentacles with the upper tentacles overlapping and tentacles going into the bell ; 3(c)(i) (as depth increases) species richness / number of species, decreases ; 2 plus any one from: (species richness) declines fastest in the first 1500 m / levels off below 1500 m ; correct manipulation of data ; 3(c)(ii) any three from: 3 1 food chains begin with phytoplankton found in surface layer ; 2 phytoplankton need light for photosynthesis ; 3 jellyfish, are consumers / eat animals, (that feed on phytoplankton) ; 4 limited motility / drift in currents so can’t move great distances to obtain food ; 5 vertical migrations / found below 500 m , to reduce being predated in light ; 6 ref. to decrease in temperature with increasing depth ; 7 AVP ; 3(c)(iii) any two from: 2 water at the surface heated (by energy form the sun) ; decreases the density of surface water ; reduced mixing with cooler, denser water below ; 3(c)(iv) idea of population (of each species) ; 1 3(c)(v) genetic diversity ; 4 (genetic diversity) variation in the genes of a species ; ecological diversity ; (ecological diversity) variation in ecosystems (on a regional and global level) ;

This question in 9693/21 Oct/Nov 2025

1 (a) Fig. 1.1 shows a species of starfish. Fig. 1.1 (i) Make a large drawing of the starfish shown in Fig. 1.1. Do not include markings. Do not label your drawing. [4] (ii) State why this starfish species is not a typical echinoderm. … … [1] (b) Starfish regrow their arms if they become damaged. Fig. 1.2 shows a different starfish species with a damaged arm. Fig. 1.2 Starfish arms can be damaged by the impact of humans. Suggest one other way a starfish arm can become damaged. … … [1] (c) Scientists investigated if the number of arms damaged affected the rate at which the arms can regrow. Starfish with damaged arms were collected from one shoreline. The starfish were placed in a tank of sea water in a laboratory and fed daily. The scientists measured the length of the damaged arms every 50 days over a period of 300 days. Fig. 1.3 shows the results. Key one arm regrowing two arms regrowing 160 140 120 100 mean length of regrowing 80 arm / mm 60 40 20 0 0 50 100 150 200 250 300 time / days Fig. 1.3 (i) Suggest one abiotic factor the scientists should keep the same as the natural environment of the starfish. … … [1] (ii) Use the line of best fit on Fig.1.3 to calculate the mean rate of growth of the damaged arm for starfish with one arm regrowing. Give your answer to two significant figures. growth rate = … mm per day [3] (iii) The scientists predicted that the mean rate of growth of damaged arms would be greater for starfish with only one damaged arm. Discuss the extent to which the results support this prediction. … … … … [2] (iv) Describe one safety and one ethical consideration for this investigation. safety … … ethical … … [2] [Total: 14]

14 marks

Mark scheme: Question Answer Marks 1(a)(i) outline: unbroken lines and no shading ; 4 size: most of the space provided and at least as big as original picture ; in proportion ; detail ; 1(a)(ii) reference to more than 5 arms OR has 7 arms ; 1 1(b) any one from: 1 lost to predator ; lost due to wave action ; lost during reproduction ; AVP ; 1(c)(i) any one from: 1 (water) temperature ; dissolved oxygen concentration ; salinity ; pH ; AVP ; 1(c)(ii) correct numbers for mm and time read from line of best fit ; 3 correct calculation of mm / time ; answer correctly rounded to 2 sig figs ; 1(c)(iii) Yes + as gradient for 1 arm re-growing is steeper than gradient for 2 arms ; 2 and one from: however, sample size not known / mean starting lengths different ; reference to significant difference / need for statistical analysis ; may have collected different species / ages / genders ; calculated difference of 0.1 mm per day ; difference in feeding ability ; no control group (growth of starfish with all limbs intact) AW ; AVP ; 1(c)(iv) safety – any one from: 2 reference to safety when collecting starfish on shoreline e.g. don’t go alone / awareness of tides / suitable footwear / using gloves to avoid stings or infection or cuts ; ethical – any one from: reference to avoidance of further damage to starfish ; provide hiding places for the starfish ; provide a rock for starfish to pull themselves out of the water ; starfish released at same shoreline they were collected from ; AVP ;

This question in 9693/22 Oct/Nov 2025

1 (a) Fig. 1.1 shows a species of starfish. Fig. 1.1 (i) Make a large drawing of the starfish shown in Fig. 1.1. Do not include markings. Do not label your drawing. [4] (ii) State why this starfish species is not a typical echinoderm. … … [1] (b) Starfish regrow their arms if they become damaged. Fig. 1.2 shows a different starfish species with a damaged arm. Fig. 1.2 Starfish arms can be damaged by the impact of humans. Suggest one other way a starfish arm can become damaged. … … [1] (c) Scientists investigated if the number of arms damaged affected the rate at which the arms can regrow. Starfish with damaged arms were collected from one shoreline. The starfish were placed in a tank of sea water in a laboratory and fed daily. The scientists measured the length of the damaged arms every 50 days over a period of 300 days. Fig. 1.3 shows the results. Key one arm regrowing two arms regrowing 160 140 120 100 mean length of regrowing 80 arm / mm 60 40 20 0 0 50 100 150 200 250 300 time / days Fig. 1.3 (i) Suggest one abiotic factor the scientists should keep the same as the natural environment of the starfish. … … [1] (ii) Use the line of best fit on Fig.1.3 to calculate the mean rate of growth of the damaged arm for starfish with one arm regrowing. Give your answer to two significant figures. growth rate = … mm per day [3] (iii) The scientists predicted that the mean rate of growth of damaged arms would be greater for starfish with only one damaged arm. Discuss the extent to which the results support this prediction. … … … … [2] (iv) Describe one safety and one ethical consideration for this investigation. safety … … ethical … … [2] [Total: 14]

14 marks

Mark scheme: Question Answer Marks 1(a)(i) outline: unbroken lines and no shading ; 4 size: most of the space provided and at least as big as original picture ; in proportion ; detail ; 1(a)(ii) reference to more than 5 arms OR has 7 arms ; 1 1(b) any one from: 1 lost to predator ; lost due to wave action ; lost during reproduction ; AVP ; 1(c)(i) any one from: 1 (water) temperature ; dissolved oxygen concentration ; salinity ; pH ; AVP ; 1(c)(ii) correct numbers for mm and time read from line of best fit ; 3 correct calculation of mm / time ; answer correctly rounded to 2 sig figs ; 1(c)(iii) Yes + as gradient for 1 arm re-growing is steeper than gradient for 2 arms ; 2 and one from: however, sample size not known / mean starting lengths different ; reference to significant difference / need for statistical analysis ; may have collected different species / ages / genders ; calculated difference of 0.1 mm per day ; difference in feeding ability ; no control group (growth of starfish with all limbs intact) AW ; AVP ; 1(c)(iv) safety – any one from: 2 reference to safety when collecting starfish on shoreline e.g. don’t go alone / awareness of tides / suitable footwear / using gloves to avoid stings or infection or cuts ; ethical – any one from: reference to avoidance of further damage to starfish ; provide hiding places for the starfish ; provide a rock for starfish to pull themselves out of the water ; starfish released at same shoreline they were collected from ; AVP ;

This question in 9693/23 Oct/Nov 2025