The open ocean — Paper 2 · A Level Marine Science 9693

4 (a) Explain how volcanic activity affects the chemical composition of sea water. … … … … … … … … … … [5] (b) Describe how temperature gradients form in water columns to produce ocean layers and how mixing of these layers may occur. … … … … … … … … … … [5] (c) The concentration of dissolved oxygen in the surface water of open oceans ranges from 4 mg dm–3 to 9 mg dm–3. The concentration of dissolved oxygen in a tropical lagoon was measured and found to be 2.9 mg dm–3. Suggest explanations for this difference. … … … … … … … … … … … … [5] [Total: 15]

15 marks

Mark scheme: 4(a) any five of: 1 idea of, (named) salt / (named) mineral input from volcanoes (increases) salinity ; 2 volcanic gases contain, carbon dioxide / sulfur dioxide / hydrogen sulfide / hydrogen chloride ; 3 gases dissolve / (atmospheric) dissolution ; 4 carried into sea water in rain water / reference to hydrological cycle ; 5 (ions) enter water directly through underwater volcano / hydrothermal vent ; 6 idea of, (sea) water becomes more acidic / decreased pH ; 7 gases are less soluble in hot water ; 8 idea of, a lot of volcanic ash would raise pH ; 5 A CO2 / SO2 / H2S / sulfides / S2– / HCl hydrochloric acid / chloride (ions) / Cl – I mixing A ref. to hydrosphere Question Answer Marks Guidance 4(b) any five of: 1 warming of surface layers ; 2 warm water less dense than cold water ; 3 (therefore) floats on colder water ; 4 temperature decreases as depth increases ; 5 ref. to thermocline / description of ; 6 (mixing by) wind / storms / cyclones / hurricanes / typhoons ; 7 (mixing by) currents / upwelling ; 8 (leads to) cooling of surface water ; 9 results in convection (mixing) ; 5 description of thermocline must imply sudden change in temp. with depth Question Answer Marks Guidance 4(c) (the concentration of DO is lower in a tropical lagoon because:) any five of: 1 higher temperature (than open ocean) ; 2 solubility of oxygen decreases (as temperature increases) ; 3 less, wave action / mixing / turbulence ; 4 waves help atmospheric oxygen to dissolve ; 5 higher salinity in a lagoon (due to evaporation) ; 6 oxygen less soluble in more saline water ; 7 fewer producers in lagoon ; 8 less (production of oxygen by) photosynthesis ; 9 higher nutrient concentration (in lagoon) / idea of, eutrophication ; 10 lagoon is an enclosed body of water (vs open ocean with lots of mixing) ; 5 Implication of a comparison is needed in the answer. A reference to a lagoon being, a closed system / isolated, or surrounded by a reef / atolls

This question in 9693/21 May/June 2017

3 (a) Explain the effect of volcanic activity on the chemical composition of sea water. … … … … … … … … … … [5] (b) Describe and explain the effects of evaporation and precipitation on the salinity of sea water. … … … … … … … … [4] (c) Explain how the concentration of dissolved oxygen varies with depth in the open ocean. … … … … … … … … … … … … [6] [Total: 15]

15 marks

Mark scheme: 3(a) any five from: 1 idea of, (named) salt / (named) mineral input from volcanoes (increases) salinity ; 2 volcanic gases contain, carbon dioxide / sulfur dioxide / hydrogen sulfide / hydrogen chloride ; 3 gases dissolve / (atmospheric) dissolution ; 4 carried into sea water in rain water / reference to hydrological cycle ; 5 (ions) enter water directly through underwater volcano / hydrothermal vent ; 6 idea of, (sea) water becomes more acidic / decreased pH ; 7 gases are less soluble in hot water ; 8 idea of, a lot of volcanic ash would raise pH ; 5 I mixing 3(b) any four from evaporation increases salinity ; evaporation removes water (leaves salt behind) ; ref. shallow seas / coastal ; direct precipitation adds (fresh) water / (fresh)-water run-off / melting glaciers (from precipitation) ; lowers salinity ; 4 effect is greater in shallow seas / along coastline 3(c) any six from high(est) at surface ; due to turbulence ; lots of producers / primary productivity (in surface layers) ; photosynthesis (releases oxygen) ; decrease with increasing depth (to oxygen minimum layer) ; lots of respiration vs photosynthesis ; usually at 500 m (allow 100 to 1000 m) ; at greater depths starts to increase ; lack of food – less respiration ; increase solubility with lower temperatures ; increasing pressure increases solubility ; 6

This question in 9693/22 May/June 2019

3 (a) Explain the effect of volcanic activity on the chemical composition of sea water. … … … … … … … … … … [5] (b) Describe and explain the effects of evaporation and precipitation on the salinity of sea water. … … … … … … … … [4] (c) Explain how the concentration of dissolved oxygen varies with depth in the open ocean. … … … … … … … … … … … … [6] [Total: 15]

15 marks

Mark scheme: 3(a) any five from: 1 idea of, (named) salt / (named) mineral input from volcanoes (increases) salinity ; 2 volcanic gases contain, carbon dioxide / sulfur dioxide / hydrogen sulfide / hydrogen chloride ; 3 gases dissolve / (atmospheric) dissolution ; 4 carried into sea water in rain water / reference to hydrological cycle ; 5 (ions) enter water directly through underwater volcano / hydrothermal vent ; 6 idea of, (sea) water becomes more acidic / decreased pH ; 7 gases are less soluble in hot water ; 8 idea of, a lot of volcanic ash would raise pH ; 5 I mixing 3(b) any four from evaporation increases salinity ; evaporation removes water (leaves salt behind) ; ref. shallow seas / coastal ; direct precipitation adds (fresh) water / (fresh)-water run-off / melting glaciers (from precipitation) ; lowers salinity ; 4 effect is greater in shallow seas / along coastline 3(c) any six from high(est) at surface ; due to turbulence ; lots of producers / primary productivity (in surface layers) ; photosynthesis (releases oxygen) ; decrease with increasing depth (to oxygen minimum layer) ; lots of respiration vs photosynthesis ; usually at 500 m (allow 100 to 1000 m) ; at greater depths starts to increase ; lack of food – less respiration ; increase solubility with lower temperatures ; increasing pressure increases solubility ; 6

This question in 9693/23 May/June 2019

3 A research boat spent six months, from July to January, monitoring the currents and conditions off the Indian coastline, where the ocean had a depth of 1000 m. (a) Describe and explain how the wind patterns would differ in this area in summer (July and August) from in winter (December and January). … … … … … … … … [4] (b) Water temperature, salinity and oxygen concentration were measured at different depths. Describe and explain how each factor would change with increasing depth. temperature … … … … … … salinity … … … … … … oxygen concentration … … … … … … [8] (c) Outline the factors that produce ocean currents. … … … … … … [3] [Total: 15]

15 marks

Mark scheme: 3(a) one of: winds reverse ; winds change direction ; any 3 from: 1 in July / Aug Asian continent / landmass warmer than sea ; 2 air over continent becomes less dense and rises ; 3 so air drawn from ocean to replace it ; 4 south-west wind created ORA for winter months Question Answer Marks 3(b) any 8 of : Temperature: 1 decrease in temperature with depth ; 2 surface waters warmer due to heat from Sun / solar radiation ; 3 reference to thermocline ; 4 as region of steep decrease ; 5 density of warmer water ; Salinity: 6 highest at surface due to evaporation ; 7 reference to halocline ; 8 as steep decrease ; 9 then slow increase with depth due to density ; Oxygen: 10 surface waters have higher concentration ; 11 due to atmospheric dissolution / photosynthesis / wave action ; 12 oxygen minimum layer due to uptake by organisms ; 13 increase in oxygen again at greater depths ; 14 due to increased solubility in cooler temperature / at higher pressure ; 8 Question Answer Marks 3(c) any 3 of: effect of wind ; temperature ; Coriolis effect… ; …explanation of ; influence of tides ; change in density ; topography of sea-bed ; 3

This question in 9693/21 May/June 2020

2 Fig. 2.1 shows the solubility of oxygen at different temperatures and pressures in sea water at the mean ocean salinity of 35 ‰. 60 50 Key 40 400 kPa dissolved 200 kPa oxygen 30 100 kPa / mg per litre 20 10 0 0 5 10 15 20 25 30 35 40 45 50 temperature / °C Fig. 2.1 (a) Use Fig. 2.1 to describe the relationship between: dissolved oxygen and temperature … … dissolved oxygen and pressure … … [2] (b) The mean temperature of the world’s oceans is 17 °C. Using Fig. 2.1, estimate the mean dissolved oxygen concentration when the water pressure is 200 kPa. Include the correct unit. … [2] (c) Fig. 2.2 shows the concentration of oxygen at different depths at two locations, one in the Atlantic Ocean and one in the Pacific Ocean. dissolved oxygen / mg per litre 0 5 10 0 1000 2000 depth / m 3000 Pacific Atlantic 4000 5000 Fig. 2.2 (i) Describe and explain the similarities between the lines for the two oceans in Fig. 2.2. … … … … … … [3] (ii) Describe and explain the differences between the lines for the two oceans in Fig. 2.2. … … … … … … [3] [Total: 10]

10 marks

Mark scheme: 2(a) (as temperature) increases dissolved oxygen decreases ; (as pressure) increases dissolved oxygen increases ; 2(b) estimate between 15–16 ; mg per litre / mg per l ; 2 2(c)(i) any three from ; concentration highest at surface for both ; due to, surface mixing / photosynthesis (by producers) ; both decrease to depth (of 500 m) ; due to, reduction in photosynthesis / impact of respiration ; both increase gradually beyond 1000 m ; due to increased pressure / decreased temperature ; idea of increase reducing beyond 3000 m ; 3 Question Answer Marks 2(c)(ii) any three from: dissolved oxygen always higher in Atlantic Ocean ; due to increased availability of light / increased light penetration / colder water temperature / increased mixing at surface / increased mixing via ocean conveyor belt / greater rate of photosynthesis / number of producers ; oxygen minimum layer / AW, found deeper in Pacific Ocean ; due to increased light penetration / warmer water in layer ; drop in concentration of oxygen in Pacific is greater ; due to lower population of producers / lower rate of photosynthesis / increased respiration ; 3

This question in 9693/22 May/June 2022

2 Fig. 2.1 shows the solubility of oxygen at different temperatures and pressures in sea water at the mean ocean salinity of 35 ‰. 60 50 Key 40 400 kPa dissolved 200 kPa oxygen 30 100 kPa / mg per litre 20 10 0 0 5 10 15 20 25 30 35 40 45 50 temperature / °C Fig. 2.1 (a) Use Fig. 2.1 to describe the relationship between: dissolved oxygen and temperature … … dissolved oxygen and pressure … … [2] (b) The mean temperature of the world’s oceans is 17 °C. Using Fig. 2.1, estimate the mean dissolved oxygen concentration when the water pressure is 200 kPa. Include the correct unit. … [2] (c) Fig. 2.2 shows the concentration of oxygen at different depths at two locations, one in the Atlantic Ocean and one in the Pacific Ocean. dissolved oxygen / mg per litre 0 5 10 0 1000 2000 depth / m 3000 Pacific Atlantic 4000 5000 Fig. 2.2 (i) Describe and explain the similarities between the lines for the two oceans in Fig. 2.2. … … … … … … [3] (ii) Describe and explain the differences between the lines for the two oceans in Fig. 2.2. … … … … … … [3] [Total: 10]

10 marks

Mark scheme: 2(a) (as temperature) increases dissolved oxygen decreases ; (as pressure) increases dissolved oxygen increases ; 2(b) estimate between 15–16 ; mg per litre / mg per l ; 2 2(c)(i) any 3 from ; concentration highest at surface for both ; due to, surface mixing / photosynthesis (by producers) ; both decrease to depth (of 500 m) ; due to, reduction in photosynthesis / impact of respiration ; both increase gradually beyond 1000 m ; due to increased pressure / decreased temperature ; idea of increase reducing beyond 3000 m ; 3 Question Answer Marks 2(c)(ii) any 3 from: dissolved oxygen always higher in Atlantic Ocean ; due to increased availability of light / increased light penetration / colder water temperature / increased mixing at surface / increased mixing via ocean conveyor belt / greater rate of photosynthesis / number of producers ; oxygen minimum layer / AW, found deeper in Pacific Ocean ; due to increased light penetration / warmer water in layer ; drop in concentration of oxygen in Pacific is greater ; due to lower population of producers / lower rate of photosynthesis / increased respiration ; 3

This question in 9693/23 May/June 2022

1 A student was given water samples from three different environments to compare. They tested the pH of the samples. (a) State two ways of measuring pH. 1 … 2 … [2] (b) The student measured the pH using two different methods. Table 1.1 shows the results. Table 1.1 pH water sample method 1 method 2 J 8.2 8.0 K 3.6 4.0 L 7.6 7.0 (i) Suggest why the student did not calculate the mean of the two methods for each sample. … … [1] Dissolved nutrients affect the pH of water. (ii) Identify which sample, J, K, or L, came from near a hydrothermal vent. … [1] (iii) Explain your answer from (ii) for the sample from the hydrothermal vent. … … … … [2] (c) Explain why the dissolved oxygen level in surface open ocean water is higher than in water near a hydrothermal vent. … … … … … … [4] [Total: 10]

10 marks

Mark scheme: Question Answer Marks 1(a) pH meter / probe ; 2 universal indicator ; 1(b)(i) any 1 from: 1 they were measured to different degrees of accuracy ; means should only be calculated when results are measured using the same method / apparatus ; 1(b)(ii) K ; 1 1(b)(iii) any 2 from: 2 water coming from hydrothermal vents has (a high concentration of) dissolved nutrient(s) / minerals / named correct chemical / ions ; which makes the water (very) acidic / pH goes below 7 ; 1(c) any 4 from: 4 light present (in surface water) ; presence of photosynthetic organisms (in surface water) ; (photosynthesis / producers) releasing oxygen (in surface water) ; atmospheric dissolution (in surface water) ; wave action increases oxygen dissolving (in surface water) ; low mixing with higher layers containing oxygen (at hydrothermal vent) ; correct ref. solubility of oxygen at different temps / OWTTE ; organisms respiring oxygen (at hydrothermal vent) ; higher pressure so solubility lower (at hydrothermal vent) ; correct ref. to solubility of oxygen at different salinities / OWTTE ;

This question in 9693/21 Oct/Nov 2022

3 Many organisms have a planktonic stage in their development. (a) Define the term plankton. … … [2] (b) Some zooplankton show a vertical swimming response towards light when a light stimulus is applied above them. These zooplankton do not swim in darkness. An investigation is carried out in a laboratory to compare the swimming speeds of zooplankton of different sizes in response to white light. A student makes the hypothesis: The swimming speed of zooplankton is proportional to their size. The maximum speed of any of the zooplankton provided is 10 mm s–1. The size range of the zooplankton is 2–10 mm. distance Speed can be calculated using the equation: speed = time (i) List the equipment required for this investigation. 1 … 2 … 3 … [3] (ii) State three key variables to standardise in this investigation. 1 … 2 … 3 … [3] (iii) Outline a method to compare the swimming speeds of zooplankton of different sizes in response to white light. … … … … … … … … … … … … … [5] (c) Use the space below to draw a suitable table to record the results from the method described in (b)(iii). Include full headings and units in the table. Do not write in any results. [2] [Total: 15]

15 marks

Mark scheme: 3(a) microscopic ; 2 drift in currents / limited motility ; 3(b)(i) any 3 from: 3 stopwatch ; ruler ; light (source) ; water container / measuring cylinder (containing water) ; AVP ; 3(b)(ii) any 3 from: 3 (same) temperature ; (same) pH ; (same) salinity ; (same) oxygen concentration ; (same) time to settle ; (same) species ; (same) volume / height of measuring cylinder / water column ; (same) intensity of light source ; (same) exposure time OR (same) distance travelled ; ref. to background light ; 3(b)(iii) any 5 from: 5 place a zooplankton in measuring cylinder containing sea water and leave in dark (to settle to the bottom) ; (place glass sheet between light source and cylinder) to ensure temperature doesn’t change ; switch on light ; record time to swim (set) distance e.g. 5 cm / analyse a video to find time OR record distance swam in a set time ; repeat 3 times + find mean ; repeat with at least 3 different sized zooplankton / 3 stated sizes ; photograph / measure, size of each zooplankton on ruler / mm scale ; accept reasonable safety precaution ; AVP ; 3(c) a column / row, headed zooplankton size / mm ; 2 PLUS any 1 from: a column / row, headed distance, cm / mm OR a column / row headed time / s OR a column / row headed speed mm / s or mm s–1 ;

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

1 A student was given water samples from three different environments to compare. They tested the pH of the samples. (a) State two ways of measuring pH. 1 … 2 … [2] (b) The student measured the pH using two different methods. Table 1.1 shows the results. Table 1.1 pH water sample method 1 method 2 J 8.2 8.0 K 3.6 4.0 L 7.6 7.0 (i) Suggest why the student did not calculate the mean of the two methods for each sample. … … [1] Dissolved nutrients affect the pH of water. (ii) Identify which sample, J, K, or L, came from near a hydrothermal vent. … [1] (iii) Explain your answer from (ii) for the sample from the hydrothermal vent. … … … … [2] (c) Explain why the dissolved oxygen level in surface open ocean water is higher than in water near a hydrothermal vent. … … … … … … [4] [Total: 10]

10 marks

Mark scheme: Question Answer Marks 1(a) pH meter / probe ; 2 universal indicator ; 1(b)(i) any 1 from: 1 they were measured to different degrees of accuracy ; means should only be calculated when results are measured using the same method / apparatus ; 1(b)(ii) K ; 1 1(b)(iii) any 2 from: 2 water coming from hydrothermal vents has (a high concentration of) dissolved nutrient(s) / minerals / named correct chemical / ions ; which makes the water (very) acidic / pH goes below 7 ; 1(c) any 4 from: 4 light present (in surface water) ; presence of photosynthetic organisms (in surface water) ; (photosynthesis / producers) releasing oxygen (in surface water) ; atmospheric dissolution (in surface water) ; wave action increases oxygen dissolving (in surface water) ; low mixing with higher layers containing oxygen (at hydrothermal vent) ; correct ref. solubility of oxygen at different temps / OWTTE ; organisms respiring oxygen (at hydrothermal vent) ; higher pressure so solubility lower (at hydrothermal vent) ; correct ref. to solubility of oxygen at different salinities / OWTTE ;

This question in 9693/22 Oct/Nov 2022

3 Many organisms have a planktonic stage in their development. (a) Define the term plankton. … … [2] (b) Some zooplankton show a vertical swimming response towards light when a light stimulus is applied above them. These zooplankton do not swim in darkness. An investigation is carried out in a laboratory to compare the swimming speeds of zooplankton of different sizes in response to white light. A student makes the hypothesis: The swimming speed of zooplankton is proportional to their size. The maximum speed of any of the zooplankton provided is 10 mm s–1. The size range of the zooplankton is 2–10 mm. distance Speed can be calculated using the equation: speed = time (i) List the equipment required for this investigation. 1 … 2 … 3 … [3] (ii) State three key variables to standardise in this investigation. 1 … 2 … 3 … [3] (iii) Outline a method to compare the swimming speeds of zooplankton of different sizes in response to white light. … … … … … … … … … … … … … [5] (c) Use the space below to draw a suitable table to record the results from the method described in (b)(iii). Include full headings and units in the table. Do not write in any results. [2] [Total: 15]

15 marks

Mark scheme: 3(a) microscopic ; 2 drift in currents / limited motility ; 3(b)(i) any 3 from: 3 stopwatch ; ruler ; light (source) ; water container / measuring cylinder (containing water) ; AVP ; 3(b)(ii) any 3 from: 3 (same) temperature ; (same) pH ; (same) salinity ; (same) oxygen concentration ; (same) time to settle ; (same) species ; (same) volume / height of measuring cylinder / water column ; (same) intensity of light source ; (same) exposure time OR (same) distance travelled ; ref. to background light ; 3(b)(iii) any 5 from: 5 place a zooplankton in measuring cylinder containing sea water and leave in dark (to settle to the bottom) ; (place glass sheet between light source and cylinder) to ensure temperature doesn’t change ; switch on light ; record time to swim (set) distance e.g. 5 cm / analyse a video to find time OR record distance swam in a set time ; repeat 3 times + find mean ; repeat with at least 3 different sized zooplankton / 3 stated sizes ; photograph / measure, size of each zooplankton on ruler / mm scale ; accept reasonable safety precaution ; AVP ; 3(c) a column / row, headed zooplankton size / mm ; 2 PLUS any 1 from: a column / row, headed distance, cm / mm OR a column / row headed time / s OR a column / row headed speed mm / s or mm s–1 ;

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

1 A student was given water samples from three different environments to compare. They tested the pH of the samples. (a) State two ways of measuring pH. 1 … 2 … [2] (b) The student measured the pH using two different methods. Table 1.1 shows the results. Table 1.1 pH water sample method 1 method 2 J 8.2 8.0 K 3.6 4.0 L 7.6 7.0 (i) Suggest why the student did not calculate the mean of the two methods for each sample. … … [1] Dissolved nutrients affect the pH of water. (ii) Identify which sample, J, K, or L, came from near a hydrothermal vent. … [1] (iii) Explain your answer from (ii) for the sample from the hydrothermal vent. … … … … [2] (c) Explain why the dissolved oxygen level in surface open ocean water is higher than in water near a hydrothermal vent. … … … … … … [4] [Total: 10]

10 marks

Mark scheme: Question Answer Marks 1(a) pH meter / probe ; 2 universal indicator ; 1(b)(i) any 1 from: 1 they were measured to different degrees of accuracy ; means should only be calculated when results are measured using the same method / apparatus ; 1(b)(ii) K ; 1 1(b)(iii) any 2 from: 2 water coming from hydrothermal vents has (a high concentration of) dissolved nutrient(s) / minerals / named correct chemical / ions ; which makes the water (very) acidic / pH goes below 7 ; 1(c) any 4 from: 4 light present (in surface water) ; presence of photosynthetic organisms (in surface water) ; (photosynthesis / producers) releasing oxygen (in surface water) ; atmospheric dissolution (in surface water) ; wave action increases oxygen dissolving (in surface water) ; low mixing with higher layers containing oxygen (at hydrothermal vent) ; correct ref. solubility of oxygen at different temps / OWTTE ; organisms respiring oxygen (at hydrothermal vent) ; higher pressure so solubility lower (at hydrothermal vent) ; correct ref. to solubility of oxygen at different salinities / OWTTE ;

This question in 9693/23 Oct/Nov 2022

3 Many organisms have a planktonic stage in their development. (a) Define the term plankton. … … [2] (b) Some zooplankton show a vertical swimming response towards light when a light stimulus is applied above them. These zooplankton do not swim in darkness. An investigation is carried out in a laboratory to compare the swimming speeds of zooplankton of different sizes in response to white light. A student makes the hypothesis: The swimming speed of zooplankton is proportional to their size. The maximum speed of any of the zooplankton provided is 10 mm s–1. The size range of the zooplankton is 2–10 mm. distance Speed can be calculated using the equation: speed = time (i) List the equipment required for this investigation. 1 … 2 … 3 … [3] (ii) State three key variables to standardise in this investigation. 1 … 2 … 3 … [3] (iii) Outline a method to compare the swimming speeds of zooplankton of different sizes in response to white light. … … … … … … … … … … … … … [5] (c) Use the space below to draw a suitable table to record the results from the method described in (b)(iii). Include full headings and units in the table. Do not write in any results. [2] [Total: 15]

15 marks

Mark scheme: 3(a) microscopic ; 2 drift in currents / limited motility ; 3(b)(i) any 3 from: 3 stopwatch ; ruler ; light (source) ; water container / measuring cylinder (containing water) ; AVP ; 3(b)(ii) any 3 from: 3 (same) temperature ; (same) pH ; (same) salinity ; (same) oxygen concentration ; (same) time to settle ; (same) species ; (same) volume / height of measuring cylinder / water column ; (same) intensity of light source ; (same) exposure time OR (same) distance travelled ; ref. to background light ; 3(b)(iii) any 5 from: 5 place a zooplankton in measuring cylinder containing sea water and leave in dark (to settle to the bottom) ; (place glass sheet between light source and cylinder) to ensure temperature doesn’t change ; switch on light ; record time to swim (set) distance e.g. 5 cm / analyse a video to find time OR record distance swam in a set time ; repeat 3 times + find mean ; repeat with at least 3 different sized zooplankton / 3 stated sizes ; photograph / measure, size of each zooplankton on ruler / mm scale ; accept reasonable safety precaution ; AVP ; 3(c) a column / row, headed zooplankton size / mm ; 2 PLUS any 1 from: a column / row, headed distance, cm / mm OR a column / row headed time / s OR a column / row headed speed mm / s or mm s–1 ;

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

3 (a) Nitrates are an important source of nitrogen. State the importance of nitrogen for marine organisms. … … [1] (b) In October 2017 researchers recorded the following data in an ocean: • temperature of the sea water • concentration of nitrate ions (NO3–) in the sea water • rate of uptake of nitrate ions from the sea water. They took readings every 40 m down to a depth of 200 m. Table 3.1 shows the recorded temperature of the sea water. Table 3.1 depth / m sea water temperature / °C 0 28.4 40 28.2 80 26.5 120 20.1 160 17.5 200 17.0 (i) Use the data in Table 3.1 to complete the graph. You should: • label the x‑axis • add a scale to the x‑axis • plot the data • draw a line of best fit. (ii) Suggest the range of depths where the thermocline is found. Explain your answer. … … … … [2] (iii) Suggest a reason why the position of the thermocline may change. … … [1] (i) Use your graph in (b)(i) and Fig. 3.1 to determine the temperature of the sea water at the maximum rate of nitrate ion uptake. … °C [1] (ii) Describe and suggest reasons for the changes in nitrate ion uptake shown in Fig. 3.1. … … … … … … [3] (d) An influx of nitrate ions caused an algal bloom, during which the population density of phytoplankton species increased. Fig. 3.2 shows the population density before and during the algal bloom in the first 20 m of sea water. phytoplankton population density 1000 cells / ml 00 2 4 6 8 4 8 depth / m 12 16 20 Key population density before algal bloom population density during algal bloom Fig. 3.2 Predict and explain the impact of the algal bloom on the trend for the rate of uptake of nitrate ions shown in Fig. 3.1. Use information from Fig. 3.1 and Fig. 3.2 in your answer. … … … … … … [3] [Total: 14]

14 marks

Mark scheme: 3(a) used (by producers as nitrogen source) for building amino acids / proteins / DNA ; 1 3(b)(i) x–axis labelled (with units) AND suitable linear scale ; all points plotted correctly  ½ small square ; suitable curved line ; 3 Question Answer Marks 3(b)(ii) within the range of 60–140 m ; (idea of) greatest change in temperature with change in depth / AW ; 2 3(b)(iii) any 1 of: seasonal change in air temperature / radiation input from Sun ; changes in currents / upwelling / mixing ; extreme weather event such as typhoon / hurricane ; 1 3(c)(i) 28.3(C) ; 1 3(c)(ii) any 3 of: rate of uptake lower in surface water due to lower concentration ; increase in uptake with depth due to increased concentration / increased number of producers ; decrease in uptake with increasing depth due to lack of producers / phytoplankton ; decrease in uptake with increasing depth due to decreasing water temperature ; 3 3(d) peak nitrate uptake will be greater ; peak abundance now three times higher… ; at a shallower depth than previous peak ; so trend may show peak at shallower depth than before algal bloom ; algal bloom near surface will reduce light intensity / block light, for algae at greater depth AW ; 3

This question in 9693/22 May/June 2023

3 (a) Nitrates are an important source of nitrogen. State the importance of nitrogen for marine organisms. … … [1] (b) In October 2017 researchers recorded the following data in an ocean: • temperature of the sea water • concentration of nitrate ions (NO3–) in the sea water • rate of uptake of nitrate ions from the sea water. They took readings every 40 m down to a depth of 200 m. Table 3.1 shows the recorded temperature of the sea water. Table 3.1 depth / m sea water temperature / °C 0 28.4 40 28.2 80 26.5 120 20.1 160 17.5 200 17.0 (i) Use the data in Table 3.1 to complete the graph. You should: • label the x‑axis • add a scale to the x‑axis • plot the data • draw a line of best fit. (ii) Suggest the range of depths where the thermocline is found. Explain your answer. … … … … [2] (iii) Suggest a reason why the position of the thermocline may change. … … [1] (i) Use your graph in (b)(i) and Fig. 3.1 to determine the temperature of the sea water at the maximum rate of nitrate ion uptake. … °C [1] (ii) Describe and suggest reasons for the changes in nitrate ion uptake shown in Fig. 3.1. … … … … … … [3] (d) An influx of nitrate ions caused an algal bloom, during which the population density of phytoplankton species increased. Fig. 3.2 shows the population density before and during the algal bloom in the first 20 m of sea water. phytoplankton population density 1000 cells / ml 00 2 4 6 8 4 8 depth / m 12 16 20 Key population density before algal bloom population density during algal bloom Fig. 3.2 Predict and explain the impact of the algal bloom on the trend for the rate of uptake of nitrate ions shown in Fig. 3.1. Use information from Fig. 3.1 and Fig. 3.2 in your answer. … … … … … … [3] [Total: 14]

14 marks

Mark scheme: 3(a) used (by producers as nitrogen source) for building amino acids / proteins / DNA ; 1 3(b)(i) x–axis labelled (with units) AND suitable linear scale ; all points plotted correctly  ½ small square ; suitable curved line ; 3 Question Answer Marks 3(b)(ii) within the range of 60–140 m ; (idea of) greatest change in temperature with change in depth / AW ; 2 3(b)(iii) any 1 of: seasonal change in air temperature / radiation input from Sun ; changes in currents / upwelling / mixing ; extreme weather event such as typhoon / hurricane ; 1 3(c)(i) 28.3(C) ; 1 3(c)(ii) any 3 of: rate of uptake lower in surface water due to lower concentration ; increase in uptake with depth due to increased concentration / increased number of producers ; decrease in uptake with increasing depth due to lack of producers / phytoplankton ; decrease in uptake with increasing depth due to decreasing water temperature ; 3 3(d) peak nitrate uptake will be greater ; peak abundance now three times higher… ; at a shallower depth than previous peak ; so trend may show peak at shallower depth than before algal bloom ; algal bloom near surface will reduce light intensity / block light, for algae at greater depth AW ; 3

This question in 9693/23 May/June 2023

1 Photosynthesis by organisms in the epipelagic zone of the oceans produces carbon-containing substances. Some of this carbon is transported to the mesopelagic zone and bathypelagic zone by the vertical movement of organisms. Fig. 1.1 shows the positions of these zones. NOT TO SCALE epipelagic mesopelagic bathypelagic Fig. 1.1 (a) Sketch a line on the axes in Fig. 1.2 to show the light intensity in the epipelagic, mesopelagic and bathypelagic zones shown in Fig. 1.1. 0 increasing light intensity 0 epipelagic zone mesopelagic zone increasing depth bathypelagic zone Fig. 1.2 [2] (b) Phytoplankton carry out photosynthesis to obtain nutrition. (i) State the word equation for photosynthesis. … [1] (ii) Name one other process used by producers to obtain nutrition. … [1] (c) Scientists investigated the effect of light intensity on the rate of photosynthesis in phytoplankton. Phytoplankton absorb light during photosynthesis. The greater the rate of photosynthesis, the faster the growth of the population. The greater the population of phytoplankton in a container, the less light is transmitted through the container. The percentage of light passing through the container can be measured using a light sensor as shown in Fig. 1.3. light sensor light sea water containing phytoplankton Fig. 1.3 (i) Identify the independent and dependent variables. independent variable … dependent variable … [1] (ii) Complete Table 1.1 to identify two key variables to standardise, and describe how these can be standardised in this investigation. Table 1.1 key variable how to standardise [3] (iii) Using the equipment shown in Fig. 1.3, outline a safe method that can be used to investigate the effect of light intensity on the rate of photosynthesis of the phytoplankton. Do not include how to standardise key variables in your answer. … … … … … … … … [4] [Total: 12]

12 marks

Mark scheme: Question Answer Marks 1(a) line at x axis (anywhere from ‘i’ at start of label to right), continuously getting closer to the y-axis as depth increases ; 2 0 near the top of the bathypelagic zone ; 1(b)(i) carbon dioxide + water → glucose + oxygen ; 1 1(b)(ii) chemosynthesis 1 1(c)(i) (independent variable) (description of variation of) light intensity 1 AND (dependent variable) light transmitted / population or growth of phytoplankton / rate of photosynthesis / AW ; 1(c)(ii) 3 key variable how to standardise any 2 in this column (for 1 1 mark for each correct answer matching a mark) stated key variable (max 2) temperature (of water) use of thermostat or water bath to maintain temp / screen or suitable method to prevent heating ; salinity (of water) idea of start with a stock solution of standard salinity to use for each trial ; volume (of water) use of (suitable) measuring equipment to measure volume ; pH idea of using stock solution / use a (pH) buffer ; turbidity / clarity, (of water) no sediment / particles / anything, that will block light ; (dissolved) CO2 (sodium) hydrogencarbonate added to make this in excess / same amount added ; (concentration of) nutrients e.g. adding same, volume / mass, of nutrients to each experiment ; (starting) description of mixed solution containing volume / mass / number / pop phytoplankton and equal ulation, of phytoplankton volumes / mass / number etc. of phytoplankton used / AW added ; type / species of use the same species / type ; phytoplankton 1(c)(ii) key variable how to standardise background light any valid description to control e.g. turn off any other lights / dark room / close blinds etc ; light sensor make sure set to zero / same initial value each (calibration / initial value) time ; distance of light sensor from using a ruler (or other valid measuring container equipment) ; time the phytoplankton is left stated duration of experiment / use of timer or for / intervals for readings stopwatch ; wavelength / colour of light use the same lamp / bulb / filter ; idea of material the use container made from same material ; container is made from 1(c)(iii) suitable safety precaution e.g. burn from lamp / electrical equipment and water ; 4 plus any 3 from: suitable method for adjusting light intensity ; use of intervals resulting in at least three values ; idea of leaving experiment for a period of time to get results ; idea of repeating at least 3 (sets of) results ; idea of adding nutrients to the vessel ;

This question in 9693/21 Oct/Nov 2024

1 Photosynthesis by organisms in the epipelagic zone of the oceans produces carbon-containing substances. Some of this carbon is transported to the mesopelagic zone and bathypelagic zone by the vertical movement of organisms. Fig. 1.1 shows the positions of these zones. NOT TO SCALE epipelagic mesopelagic bathypelagic Fig. 1.1 (a) Sketch a line on the axes in Fig. 1.2 to show the light intensity in the epipelagic, mesopelagic and bathypelagic zones shown in Fig. 1.1. 0 increasing light intensity 0 epipelagic zone mesopelagic zone increasing depth bathypelagic zone Fig. 1.2 [2] (b) Phytoplankton carry out photosynthesis to obtain nutrition. (i) State the word equation for photosynthesis. … [1] (ii) Name one other process used by producers to obtain nutrition. … [1] (c) Scientists investigated the effect of light intensity on the rate of photosynthesis in phytoplankton. Phytoplankton absorb light during photosynthesis. The greater the rate of photosynthesis, the faster the growth of the population. The greater the population of phytoplankton in a container, the less light is transmitted through the container. The percentage of light passing through the container can be measured using a light sensor as shown in Fig. 1.3. light sensor light sea water containing phytoplankton Fig. 1.3 (i) Identify the independent and dependent variables. independent variable … dependent variable … [1] (ii) Complete Table 1.1 to identify two key variables to standardise, and describe how these can be standardised in this investigation. Table 1.1 key variable how to standardise [3] (iii) Using the equipment shown in Fig. 1.3, outline a safe method that can be used to investigate the effect of light intensity on the rate of photosynthesis of the phytoplankton. Do not include how to standardise key variables in your answer. … … … … … … … … [4] [Total: 12]

12 marks

Mark scheme: Question Answer Marks 1(a) line at x axis (anywhere from ‘i’ at start of label to right), continuously getting closer to the y-axis as depth increases ; 2 0 near the top of the bathypelagic zone ; 1(b)(i) carbon dioxide + water → glucose + oxygen ; 1 1(b)(ii) chemosynthesis 1 1(c)(i) (independent variable) (description of variation of) light intensity 1 AND (dependent variable) light transmitted / population or growth of phytoplankton / rate of photosynthesis / AW ; 1(c)(ii) 3 key variable how to standardise any 2 in this column (for 1 1 mark for each correct answer matching a mark) stated key variable (max 2) temperature (of water) use of thermostat or water bath to maintain temp / screen or suitable method to prevent heating ; salinity (of water) idea of start with a stock solution of standard salinity to use for each trial ; volume (of water) use of (suitable) measuring equipment to measure volume ; pH idea of using stock solution / use a (pH) buffer ; turbidity / clarity, (of water) no sediment / particles / anything, that will block light ; (dissolved) CO2 (sodium) hydrogencarbonate added to make this in excess / same amount added ; (concentration of) nutrients e.g. adding same, volume / mass, of nutrients to each experiment ; (starting) description of mixed solution containing volume / mass / number / pop phytoplankton and equal ulation, of phytoplankton volumes / mass / number etc. of phytoplankton used / AW added ; type / species of use the same species / type ; phytoplankton 1(c)(ii) key variable how to standardise background light any valid description to control e.g. turn off any other lights / dark room / close blinds etc ; light sensor make sure set to zero / same initial value each (calibration / initial value) time ; distance of light sensor from using a ruler (or other valid measuring container equipment) ; time the phytoplankton is left stated duration of experiment / use of timer or for / intervals for readings stopwatch ; wavelength / colour of light use the same lamp / bulb / filter ; idea of material the use container made from same material ; container is made from 1(c)(iii) suitable safety precaution e.g. burn from lamp / electrical equipment and water ; 4 plus any 3 from: suitable method for adjusting light intensity ; use of intervals resulting in at least three values ; idea of leaving experiment for a period of time to get results ; idea of repeating at least 3 (sets of) results ; idea of adding nutrients to the vessel ;

This question in 9693/22 Oct/Nov 2024

1 Photosynthesis by organisms in the epipelagic zone of the oceans produces carbon-containing substances. Some of this carbon is transported to the mesopelagic zone and bathypelagic zone by the vertical movement of organisms. Fig. 1.1 shows the positions of these zones. NOT TO SCALE epipelagic mesopelagic bathypelagic Fig. 1.1 (a) Sketch a line on the axes in Fig. 1.2 to show the light intensity in the epipelagic, mesopelagic and bathypelagic zones shown in Fig. 1.1. 0 increasing light intensity 0 epipelagic zone mesopelagic zone increasing depth bathypelagic zone Fig. 1.2 [2] (b) Phytoplankton carry out photosynthesis to obtain nutrition. (i) State the word equation for photosynthesis. … [1] (ii) Name one other process used by producers to obtain nutrition. … [1] (c) Scientists investigated the effect of light intensity on the rate of photosynthesis in phytoplankton. Phytoplankton absorb light during photosynthesis. The greater the rate of photosynthesis, the faster the growth of the population. The greater the population of phytoplankton in a container, the less light is transmitted through the container. The percentage of light passing through the container can be measured using a light sensor as shown in Fig. 1.3. light sensor light sea water containing phytoplankton Fig. 1.3 (i) Identify the independent and dependent variables. independent variable … dependent variable … [1] (ii) Complete Table 1.1 to identify two key variables to standardise, and describe how these can be standardised in this investigation. Table 1.1 key variable how to standardise [3] (iii) Using the equipment shown in Fig. 1.3, outline a safe method that can be used to investigate the effect of light intensity on the rate of photosynthesis of the phytoplankton. Do not include how to standardise key variables in your answer. … … … … … … … … [4] [Total: 12]

12 marks

Mark scheme: Question Answer Marks 1(a) line at x axis (anywhere from ‘i’ at start of label to right), continuously getting closer to the y-axis as depth increases ; 2 0 near the top of the bathypelagic zone ; 1(b)(i) carbon dioxide + water → glucose + oxygen ; 1 1(b)(ii) chemosynthesis 1 1(c)(i) (independent variable) (description of variation of) light intensity 1 AND (dependent variable) light transmitted / population or growth of phytoplankton / rate of photosynthesis / AW ; 1(c)(ii) 3 key variable how to standardise any 2 in this column (for 1 1 mark for each correct answer matching a mark) stated key variable (max 2) temperature (of water) use of thermostat or water bath to maintain temp / screen or suitable method to prevent heating ; salinity (of water) idea of start with a stock solution of standard salinity to use for each trial ; volume (of water) use of (suitable) measuring equipment to measure volume ; pH idea of using stock solution / use a (pH) buffer ; turbidity / clarity, (of water) no sediment / particles / anything, that will block light ; (dissolved) CO2 (sodium) hydrogencarbonate added to make this in excess / same amount added ; (concentration of) nutrients e.g. adding same, volume / mass, of nutrients to each experiment ; (starting) description of mixed solution containing volume / mass / number / pop phytoplankton and equal ulation, of phytoplankton volumes / mass / number etc. of phytoplankton used / AW added ; type / species of use the same species / type ; phytoplankton 1(c)(ii) key variable how to standardise background light any valid description to control e.g. turn off any other lights / dark room / close blinds etc ; light sensor make sure set to zero / same initial value each (calibration / initial value) time ; distance of light sensor from using a ruler (or other valid measuring container equipment) ; time the phytoplankton is left stated duration of experiment / use of timer or for / intervals for readings stopwatch ; wavelength / colour of light use the same lamp / bulb / filter ; idea of material the use container made from same material ; container is made from 1(c)(iii) suitable safety precaution e.g. burn from lamp / electrical equipment and water ; 4 plus any 3 from: suitable method for adjusting light intensity ; use of intervals resulting in at least three values ; idea of leaving experiment for a period of time to get results ; idea of repeating at least 3 (sets of) results ; idea of adding nutrients to the vessel ;

This question in 9693/23 Oct/Nov 2024

5 Scientists studied the biodiversity at eight locations in the Arabian Sea. The scientists used a net to catch species in the benthic zone. (a) Describe what is meant by the benthic zone. … … [1] At each location the nets were pulled at a constant speed for one hour. Four of the locations sampled were at a depth of 200 m. The other four locations sampled were at a depth of 1000 m. Table 5.1 shows the depth and total catch at each location. Table 5.1 location depth / m total catch / kg number 1 200 169 2 200 122 3 200 34 4 200 582 5 1000 75 6 1000 453 7 1000 256 8 1000 120 (b) Use the data shown in Table 5.1 to describe if there is a relationship between depth and total catch. … … … … [2] (c) The scientists identified the species present in each catch and the number of individuals of each species. They used this data to calculate Simpson’s index of diversity using the equation: 2 D = 1 – (Σ(nN) ) = sum of (total) Σ n = number of individuals of each different species N = the total number of individuals of all the species (i) Use the data provided to complete Table 5.2 for location 1. Give your answers to three significant figures. Table 5.2 location 1 species 2 n n n N ( N) P 27 0.278 0.077 Q 23 … … R 18 0.186 0.034 S 16 0.165 0.027 T 13 0.134 0.018 N 97 Σ … [4] (ii) Use your answer to (c)(i) to calculate Simpson’s index of diversity for location 1. … [1] (d) Table 5.3 shows the Simpson’s index of diversity calculated for each other location sampled. Table 5.3 Simpson’s location depth / m total catch / kg index of number diversity 1 200 169 2 200 122 0.88 3 200 34 0.92 4 200 582 0.68 5 1000 75 0.91 6 1000 453 0.71 7 1000 256 0.78 8 1000 120 0.91 Compare the biodiversity for the catches shown in Table 5.3. … … … … … … [3] [Total: 11]

11 marks

Mark scheme: 5(a) the lowest part of the ocean (sediments / water) ; 1 5(b) any two from: 2 no, correlation / relationship, + no, trend / pattern / consistency, in results ; more data required to establish a relationship ; possible anomalies at site 3 / 4 and 5 ; relevant use of data to support ; 5(c)(i) 4 location 1 species 2 n n  n    N  N  Q 23 0.237 ; 0.056(0) ; N 97  0.212 ; n values for AND  to 3 sig. fig ; N 5(c)(ii) 0.788 ; 1 5(d) any three from: 3 higher Simpson’s index, value / number, indicates a, greater / higher, biodiversity ORA ; results suggest smaller catches have a higher biodiversity ORA ; results suggest no significant difference between biodiversity at different depths ; use of at least 2 data to support answer ;

This question in 9693/21 Oct/Nov 2025