Investigating ecosystems — Paper 2 · IGCSE Marine Science (Maldives only) 0697

2 Fig. 2.1 shows a food chain. algae damselfish lionfish reef shark Fig. 2.1 (a) Draw a pyramid of biomass for the food chain shown in Fig. 2.1. [2] (b) Some species of damselfish shelter in coral reefs. These damselfish feed on algae that grows over the surface of photosynthetic coral polyps. This is an example of symbiosis. (i) Explain how the ecological relationship between the damselfish and the coral shows symbiosis. … … … … … … [3] Fig. 2.2 shows part of a food web on a coral reef. algae damselfish lionfish reef shark coral polyp parrotfish Fig. 2.2 (ii) Use Fig. 2.2 to explain why coral mining decreases the biodiversity of this coral reef. … … … … … … [3] (c) A student investigates the effect of predator number on the shoaling behaviour of damselfish. The student is given plastic models of damselfish predators. The student places five damselfish into a tank. The mean distance between the damselfish is calculated. The mean swimming speed of the damselfish is also calculated. This is repeated with different numbers of predator models in the tank. The results are shown in Table 2.1. Table 2.1 number of mean distance between mean swimming speed of predator models damselfish / mm damselfish / mm per s 0 52 24 1 22 …… 2 18 36 3 17 35 (i) The swimming speeds of five damselfish when one predator model is present are shown in Table 2.2. Table 2.2 swimming speed / mm per s 29 31 28 29 30 Calculate the mean swimming speed for the five damselfish and write your answer in the space in Table 2.1. [2] (ii) Describe the effect of number of predator models on the mean distance between damselfish. … … … … [2] (iii) Suggest an explanation for the behaviour of the damselfish in the experiment. … … … … … … [3] [Total: 15]

15 marks

This question in 0697/20 May/June 2021

1 Anchovies are small pelagic fish that feed on plankton. Skipjack tuna are predatory fish that feed on many species, including anchovies. Scientists analysed the catch of anchovies and the catch of skipjack tuna from an area of the Pacific Ocean over five years. The results are shown in Table 1.1. Table 1.1 catch of fish / thousand kg year anchovies skipjack tuna 2012 25 10 2013 35 15 2014 50 22 2015 25 30 2016 10 25 (a) (i) Plot a graph to show the catch of anchovies and the catch of skipjack tuna between 2012 and 2016. Join the points for each set of data with ruled, straight lines. [5] (ii) Describe the change in catch of anchovies between 2012 and 2016. … … … … [2] (iii) Use the data in Table 1.1 to suggest why the catch of skipjack tuna changed between 2012 and 2016. … … … … … … [3] (b) Scientists examined the gut contents of the skipjack tuna. The percentage of skipjack tuna with anchovies in their gut is shown in Table 1.2. Table 1.2 year percentage of skipjack tuna with anchovies in their gut 2012 75 2013 85 2014 65 2015 55 2016 (i) In 2016, 500 skipjack tuna were analysed and 210 were found to have anchovies in their gut. Calculate the percentage of skipjack tuna with anchovies in their gut in 2016. … % [1] (ii) Suggest two reasons why gut content analysis of the skipjack tuna may not be an accurate measure of the population of anchovies. 1 … … 2 … … [2] (c) Suggest two methods used by a government to keep the fishing of anchovies sustainable. 1 … … 2 … … [2] [Total: 15]

15 marks

This question in 0697/20 May/June 2023

4 A student investigates the distribution of lugworms and clams in the intertidal zone of a sandy shore from the low tide level towards the high tide level. Table 4.1 shows the data collected. Table 4.1 number of organisms per m2 distance from low tide level / m lugworm clam 0 10 8 5 8 14 10 4 12 15 1 6 20 0 2 (a) (i) Draw a line graph to show the numbers of lugworms and clams between 0 m and 20 m from the low tide level, as shown in Table 4.1. Join your points for each set of data with ruled, straight lines. Label each line clearly. 0 5 10 15 20 distance from low tide level / m [5] (ii) Compare the distributions of lugworms and clams along the shore. … … … … [2] (iii) Outline a method to collect the data in Table 4.1. … … … … … … [3] (b) Explain how lugworms are adapted to live on sandy shores. … … … … … … … … [4] [Total: 14] Question 5 starts on the next page.

14 marks

Mark scheme: 4(a)(i) linear scale for y-axis that uses at least half of axis ; labelled axis and key ; both sets of points plotted ; ; points joined by straight lines ; 4(a)(ii) any 2 of: both decrease higher up the beach / AW ; lugworms are higher (than clams) at, low tide mark / at 0m / AW ; clams increase and then decrease ; (generally) more clams than lugworms / AW ; 2 4(a)(iii) any 3 of: use of quadrat ; run a line transect / AW ; sample at intervals ; count number of both species / AW ; 3 Question Answer Marks 4(b) any 4 of: live in U-shaped burrow / able to burrow ; which has low oxygen ; contain haemoglobin ; (haemoglobin) binds to oxygen ; ingest / eat, sand / sediment / AW ; 4

This question in 0697/21 May/June 2024

3 Rocky shores can be divided up into different zones. Each zone has different abiotic factors that affect the distribution of organisms. (a) Fig. 3.1 shows a diagram of a rocky shore. high-tide level low-tide level sea zone X zone Y zone Z Fig. 3.1 State the names of the zones labelled X, Y and Z. zone X … zone Y … zone Z … [1] (b) A student investigates the distribution of limpets and the macroalgae Fucus sp. on a rocky shore. The student carries out systematic sampling of these species, from the low‑tide level up the shore to the high‑tide level. The student’s results are shown in Fig. 3.2. limpets Fucus sp. number of limpets percentage cover per square metre with Fucus sp. 0 10 20 30 40 50 60 distance along shore / m low-tide level high-tide level Fig. 3.2 (i) Outline a systematic sampling method to collect the results for the limpets as shown in Fig. 3.2. … … … … … … … … [3] (ii) Suggest why the student measured the percentage cover of rocks with Fucus sp. rather than counting the number per square metre. … … [1] (iii) Discuss reasons for the change in the number of limpets per square metre along the rocky shore. Use Fig. 3.2 and your own knowledge to support your answer. … … … … … … … … … … [4] (c) Sea anemones are also found on rocky shores. Explain how sea anemones are adapted to live on rocky shores. … … … … … … [3] [Total: 12]

12 marks

Mark scheme: 3(a) X: subtidal (zone), Y: intertidal (zone), Z: supratidal (zone) ; Question Answer Marks 3(b)(i) any 3 of: lay out a transect / AW ; reference to use of a quadrat ; place (quadrat) at (regular) intervals ; count number (of limpets in) (each quadrat) ; 3 3(b)(ii) idea of it is not easy to see, individual organisms / not distinct organisms / AW ; 1 3(b)(iii) any 4 of: limpets are high near low tide level / AW / ORA ; as less likely to dry out (lower down shore) / have more access to water / are less exposed to sunlight / air / wind / more time covered by water / ORA / AW ; limpets shelter under Fucus sp. / seaweed / AW ; warmer / higher temperature / more stable, conditions lower down shore / AW / ORA ; limpets eat Fucus sp. / seaweed / AW ; less predation when lower down shore / AW ; limpets are not dislodged by tides / waves (so can live in lower areas of shore) / AW ; 4 Question Answer Marks 3(c) any 3 of: live in rock pools / crevices / overhangs / shaded sides of outcrops / AW ; live under seaweed / macroalgae ; retract tentacles / close up / AW ; avoid drying out / prevent water loss / AW ; attach to rocks / substrate / stick to rocks / AW ; so not dislodged by tides / waves / AW ; 3

This question in 0697/22 May/June 2024

3 Rocky shores can be divided up into different zones. Each zone has different abiotic factors that affect the distribution of organisms. (a) Fig. 3.1 shows a diagram of a rocky shore. high-tide level low-tide level sea zone X zone Y zone Z Fig. 3.1 State the names of the zones labelled X, Y and Z. zone X … zone Y … zone Z … [1] (b) A student investigates the distribution of limpets and the macroalgae Fucus sp. on a rocky shore. The student carries out systematic sampling of these species, from the low‑tide level up the shore to the high‑tide level. The student’s results are shown in Fig. 3.2. limpets Fucus sp. number of limpets percentage cover per square metre with Fucus sp. 0 10 20 30 40 50 60 distance along shore / m low-tide level high-tide level Fig. 3.2 (i) Outline a systematic sampling method to collect the results for the limpets as shown in Fig. 3.2. … … … … … … … … [3] (ii) Suggest why the student measured the percentage cover of rocks with Fucus sp. rather than counting the number per square metre. … … [1] (iii) Discuss reasons for the change in the number of limpets per square metre along the rocky shore. Use Fig. 3.2 and your own knowledge to support your answer. … … … … … … … … … … [4] (c) Sea anemones are also found on rocky shores. Explain how sea anemones are adapted to live on rocky shores. … … … … … … [3] [Total: 12]

12 marks

Mark scheme: 3(a) X: subtidal (zone), Y: intertidal (zone), Z: supratidal (zone) ; Question Answer Marks 3(b)(i) any 3 of: lay out a transect / AW ; reference to use of a quadrat ; place (quadrat) at (regular) intervals ; count number (of limpets in) (each quadrat) ; 3 3(b)(ii) idea of it is not easy to see, individual organisms / not distinct organisms / AW ; 1 3(b)(iii) any 4 of: limpets are high near low tide level / AW / ORA ; as less likely to dry out (lower down shore) / have more access to water / are less exposed to sunlight / air / wind / more time covered by water / ORA / AW ; limpets shelter under Fucus sp. / seaweed / AW ; warmer / higher temperature / more stable, conditions lower down shore / AW / ORA ; limpets eat Fucus sp. / seaweed / AW ; less predation when lower down shore / AW ; limpets are not dislodged by tides / waves (so can live in lower areas of shore) / AW ; 4 Question Answer Marks 3(c) any 3 of: live in rock pools / crevices / overhangs / shaded sides of outcrops / AW ; live under seaweed / macroalgae ; retract tentacles / close up / AW ; avoid drying out / prevent water loss / AW ; attach to rocks / substrate / stick to rocks / AW ; so not dislodged by tides / waves / AW ; 3

This question in 0697/23 May/June 2024

2 A student investigates the effect of temperature on the solubility of carbon dioxide gas in water. The student uses this method. • Place a bottle of fizzy, carbonated water in a refrigerator at a temperature of 4 °C. • Pour 100 cm3 of the carbonated water into a beaker. • Measure the mass of the beaker and carbonated water. • Place the beaker into a water-bath at a temperature of 5 °C, as shown in Fig. 2.1. • Leave the carbonated water, stirring it occasionally until it stops releasing bubbles of carbon dioxide gas. • Reweigh the beaker and the carbonated water. • Calculate the change in mass. • Repeat the experiment at other temperatures up to 50 °C. beaker thermometer carbonated water with gas bubbles water-bath Fig. 2.1 (a) (i) Name one piece of apparatus that the student can use to measure 100 cm3 of carbonated water. … [1] (ii) Suggest two changes to the student’s method to obtain more accurate results. 1 … … 2 … … [2] (b) Fig. 2.2 shows a graph of the student’s results. temperature of water-bath / °C 0 10 20 30 40 50 0.00 – 0.05 – 0.10 change in – 0.15 mass / g – 0.20 – 0.25 – 0.30 Fig. 2.2 Explain the effect of increasing the temperature on the change in mass shown in Fig. 2.2. … … … … … … [3] (c) Explain why warm water usually lies above cold water in the ocean. … … … … … … [3] [Total: 9]

9 marks

Mark scheme: 2(a)(i) measuring cylinder ; 1 2(a)(ii) any 2 from: 2 1 dry beaker before weighing it / AW ; 2 stir for set time / set number of stirs / AW ; 3 repeat / calculate mean / AW ; 4 measure temperature in beaker (rather than in water bath) / AW ; 5 use thermostatically controlled water bath / electronic water bath / AW ; 2(b) any 3 from: 3 1 (as temperature increases) mass (of water) decreases (more) / AW ; 2 because the carbon dioxide is less soluble / less solubility / AW ; 3 more kinetic energy / AW ; 4 more carbon dioxide released / AW ; 2(c) any 3 from: 3 1 warm water has a lower density / ORA / AW ; 2 so warm water, rises / floats / AW / ORA ; 3 in warm water particles have more kinetic energy / ORA ; 4 water / particles, move more / move faster / AW / ORA ; 5 particles are / water is, more spread out / AW / ORA;

This question in 0697/21 May/June 2025

3 Fig. 3.1 shows an ocean food web. sharks tuna lancetfish mackerel shrimps copepods dinoflagellates Fig. 3.1 (a) (i) Name one primary consumer in the food web shown in Fig. 3.1. … [1] (ii) Draw the longest food chain in the food web shown in Fig. 3.1. [2] (b) Fig. 3.2 shows a dinoflagellate from this ocean food web. X Fig. 3.2 (i) In the space, make a large, accurate drawing of the dinoflagellate shown in Fig. 3.2. Do not draw internal structures of the dinoflagellate. [4] (ii) The magnification of the image in Fig. 3.2 is ×360. Calculate the actual length of the dinoflagellate in Fig. 3.2 along the length of the line labelled X. Give your answer in mm and to two significant figures. Show your working. actual length = … mm [3] (iii) State the kingdom that dinoflagellates belong to. … [1] (iv) All dinoflagellates have two flagella. Give one other main feature of dinoflagellates. … [1] (c) (i) Dinoflagellate blooms can occur at different times of the year. Outline how a Secchi disc can be used to compare population sizes of dinoflagellates. … … … … … … [3] (ii) Suggest one reason why using a Secchi disc does not provide an accurate measure of the population size of dinoflagellates. … … [1] [Total: 16]

16 marks

Mark scheme: 3(a)(i) shrimps / copepods / mackerel ; 1 3(a)(ii) dinoflagellates, copepods, mackerel, lancetfish, tuna, shark ; 2 correct direction of arrows ; 3(b)(i) 1 clear edges with no breaks and no shading ; 4 2 large diagram that is at least size of image ; 3 correct proportions (tail must be at least same length as body AND two points must point backwards) ; 4 three clear points attached to body ; 3(b)(ii) 0.27 ;;; (3 marks) 3 0.26(6666….) ;; (2 marks) 360 OR 96 (mm) OR 9.6 cm ; (1 mark) 3(b)(iii) protoctists ; 1 3(b)(iv) any 1 from: 1 microscopic / can only be seen with a microscope / AW ; single-celled ; chloroplasts present / chlorophyll ; 3(c)(i) any 3 from: 3 1 lower (Secchi) disc (into water) until it cannot be seen / AW ; 2 record length (of rope) / mark point on rope / AW ; 3 (after lowering it further) raise disc until it is seen AND record length of rope / mark rope (again) / AW ; 4 calculate, mean / average, length / AW ; 5 longer length (of rope) indicates lower population (size) / ORA / AW ; 3(c)(ii) any 1 from: 1 1 other substances / sediment may be causing cloudiness / AW ; 2 other algal species / other organisms may affect results / AW ; 3 the (Secchi) disc measures turbidity / cloudiness / clarity / light penetration, (not population) / AW ; 4 idea that seeing (Secchi) disc is subjective / depends on angle of sight / AW ; 5 light intensity may vary / AW ;

This question in 0697/21 May/June 2025

5 Fig. 5.1 shows an oil tanker. Fig. 5.1 (a) Oil tankers must be built in line with the MARPOL standards for ship design. Describe how the MARPOL standards reduce the environmental impacts of transporting oil. … … … … … … … [3] (b) Dispersant sprays contain chemicals that are used to scatter oil through water following an oil spill. Scientists investigated how changing the ratio of dispersant to oil affects the dispersal effectiveness. The scientists’ results are shown in Table 5.1. Table 5.1 ratio of dispersal effectiveness dispersant to oil / arbitrary units 0.00 0.15 0.01 0.25 0.05 0.55 0.10 0.60 0.15 0.62 0.20 0.62 (i) Draw a line graph to show how increasing the ratio of dispersant to oil affects the dispersal effectiveness. Join your points with ruled, straight lines. [4] (ii) Use the information in Table 5.1 to describe the effect of increasing the ratio of dispersant to oil on the dispersal effectiveness. … … … … [2] (iii) The ratio of dispersant to oil is calculated using the formula shown. mass of dispersant ratio of dispersant to oil = mass of oil Use the information in Table 5.1 to calculate the mass of dispersant needed to produce a dispersal effectiveness of 0.55 if 5000 kg of oil is spilled into water. Show your working and state the unit. mass of dispersant = … [2] (iv) The scientists stated that a ratio of dispersant to oil of 0.05 is the best ratio to use to scatter oil following an oil spill. Suggest why the scientists stated that this is the best ratio to use. … … … … [2] (c) Wind turbines placed into areas of ocean can provide a renewable source of energy. Discuss the environmental advantages and disadvantages of using wind turbines placed into oceans. … … … … … … … … … … … … … [4] [Total: 17]

17 marks

Mark scheme: 5(a) any 3 from: 3 1 double hulls ; 2 to reduce risk of oil leaks (after collision) / AW ; 3 only wash out hold at special collection sites / AW ; 4 control of sewage release / AW ; 5 control of garbage disposal / AW ; 5(b)(i) 1 linear scales on both axes ; 4 2 axes labelled with units ; 3 plots correct ; 4 straight lines joining points ; 5(b)(ii) (dispersal effectiveness) increases ; 2 levels off, after ratio of 0.10 / from ratio of 0.15 / AW ; 5(b)(iii) 0.05  5000 = 250 ; 2 kg ; 5(b)(iv) any 2 from: 2 1 increasing mass of dispersant has little effect beyond this / AW ; 2 dispersants are toxic / AW ; 3 using less (dispersant) reduces environmental impact / AW ; 4 reduces costs / AW ; 5(c) up to 3 from: 4 1 infinite source of energy / not used up / will not run out / AW ; 2 reduces reliance on fossil fuel / less oil used / AW ; 3 reduces carbon dioxide release / AW ; 4 less need to transport oil / reduced risk of oil spills / less damage to seabed from drilling ; and up to 3 from: 5 limited number of locations (can be used) / may not be windy / (severe) weather may damage turbines / AW ; 6 (turbines) need cables on seabed / installations damage seabed / AW ; 7 example of how marine life damages by turbines ; 8 conflict with (eco)tourism / AW ; 9 high startup cost/maintenance cost / AW ; max 4

This question in 0697/21 May/June 2025

2 A student investigates the effect of temperature on the solubility of carbon dioxide gas in water. The student uses this method. • Place a bottle of fizzy, carbonated water in a refrigerator at a temperature of 4 °C. • Pour 100 cm3 of the carbonated water into a beaker. • Measure the mass of the beaker and carbonated water. • Place the beaker into a water-bath at a temperature of 5 °C, as shown in Fig. 2.1. • Leave the carbonated water, stirring it occasionally until it stops releasing bubbles of carbon dioxide gas. • Reweigh the beaker and the carbonated water. • Calculate the change in mass. • Repeat the experiment at other temperatures up to 50 °C. beaker thermometer carbonated water with gas bubbles water-bath Fig. 2.1 (a) (i) Name one piece of apparatus that the student can use to measure 100 cm3 of carbonated water. … [1] (ii) Suggest two changes to the student’s method to obtain more accurate results. 1 … … 2 … … [2] (b) Fig. 2.2 shows a graph of the student’s results. temperature of water-bath / °C 0 10 20 30 40 50 0.00 – 0.05 – 0.10 change in – 0.15 mass / g – 0.20 – 0.25 – 0.30 Fig. 2.2 Explain the effect of increasing the temperature on the change in mass shown in Fig. 2.2. … … … … … … [3] (c) Explain why warm water usually lies above cold water in the ocean. … … … … … … [3] [Total: 9]

9 marks

Mark scheme: 2(a)(i) measuring cylinder ; 1 2(a)(ii) any 2 from: 2 1 dry beaker before weighing it / AW ; 2 stir for set time / set number of stirs / AW ; 3 repeat / calculate mean / AW ; 4 measure temperature in beaker (rather than in water bath) / AW ; 5 use thermostatically controlled water bath / electronic water bath / AW ; 2(b) any 3 from: 3 1 (as temperature increases) mass (of water) decreases (more) / AW ; 2 because the carbon dioxide is less soluble / less solubility / AW ; 3 more kinetic energy / AW ; 4 more carbon dioxide released / AW ; 2(c) any 3 from: 3 1 warm water has a lower density / ORA / AW ; 2 so warm water, rises / floats / AW / ORA ; 3 in warm water particles have more kinetic energy / ORA ; 4 water / particles, move more / move faster / AW / ORA ; 5 particles are / water is, more spread out / AW / ORA;

This question in 0697/22 May/June 2025

3 Fig. 3.1 shows an ocean food web. sharks tuna lancetfish mackerel shrimps copepods dinoflagellates Fig. 3.1 (a) (i) Name one primary consumer in the food web shown in Fig. 3.1. … [1] (ii) Draw the longest food chain in the food web shown in Fig. 3.1. [2] (b) Fig. 3.2 shows a dinoflagellate from this ocean food web. X Fig. 3.2 (i) In the space, make a large, accurate drawing of the dinoflagellate shown in Fig. 3.2. Do not draw internal structures of the dinoflagellate. [4] (ii) The magnification of the image in Fig. 3.2 is ×360. Calculate the actual length of the dinoflagellate in Fig. 3.2 along the length of the line labelled X. Give your answer in mm and to two significant figures. Show your working. actual length = … mm [3] (iii) State the kingdom that dinoflagellates belong to. … [1] (iv) All dinoflagellates have two flagella. Give one other main feature of dinoflagellates. … [1] (c) (i) Dinoflagellate blooms can occur at different times of the year. Outline how a Secchi disc can be used to compare population sizes of dinoflagellates. … … … … … … [3] (ii) Suggest one reason why using a Secchi disc does not provide an accurate measure of the population size of dinoflagellates. … … [1] [Total: 16]

16 marks

Mark scheme: 3(a)(i) shrimps / copepods / mackerel ; 1 3(a)(ii) dinoflagellates, copepods, mackerel, lancetfish, tuna, shark ; 2 correct direction of arrows ; 3(b)(i) 1 clear edges with no breaks and no shading ; 4 2 large diagram that is at least size of image ; 3 correct proportions (tail must be at least same length as body AND two points must point backwards) ; 4 three clear points attached to body ; 3(b)(ii) 0.27 ;;; (3 marks) 3 0.26(6666….) ;; (2 marks) 360 OR 96 (mm) OR 9.6 cm ; (1 mark) 3(b)(iii) protoctists ; 1 3(b)(iv) any 1 from: 1 microscopic / can only be seen with a microscope / AW ; single-celled ; chloroplasts present / chlorophyll ; 3(c)(i) any 3 from: 3 1 lower (Secchi) disc (into water) until it cannot be seen / AW ; 2 record length (of rope) / mark point on rope / AW ; 3 (after lowering it further) raise disc until it is seen AND record length of rope / mark rope (again) / AW ; 4 calculate, mean / average, length / AW ; 5 longer length (of rope) indicates lower population (size) / ORA / AW ; 3(c)(ii) any 1 from: 1 1 other substances / sediment may be causing cloudiness / AW ; 2 other algal species / other organisms may affect results / AW ; 3 the (Secchi) disc measures turbidity / cloudiness / clarity / light penetration, (not population) / AW ; 4 idea that seeing (Secchi) disc is subjective / depends on angle of sight / AW ; 5 light intensity may vary / AW ;

This question in 0697/22 May/June 2025

5 Fig. 5.1 shows an oil tanker. Fig. 5.1 (a) Oil tankers must be built in line with the MARPOL standards for ship design. Describe how the MARPOL standards reduce the environmental impacts of transporting oil. … … … … … … … [3] (b) Dispersant sprays contain chemicals that are used to scatter oil through water following an oil spill. Scientists investigated how changing the ratio of dispersant to oil affects the dispersal effectiveness. The scientists’ results are shown in Table 5.1. Table 5.1 ratio of dispersal effectiveness dispersant to oil / arbitrary units 0.00 0.15 0.01 0.25 0.05 0.55 0.10 0.60 0.15 0.62 0.20 0.62 (i) Draw a line graph to show how increasing the ratio of dispersant to oil affects the dispersal effectiveness. Join your points with ruled, straight lines. [4] (ii) Use the information in Table 5.1 to describe the effect of increasing the ratio of dispersant to oil on the dispersal effectiveness. … … … … [2] (iii) The ratio of dispersant to oil is calculated using the formula shown. mass of dispersant ratio of dispersant to oil = mass of oil Use the information in Table 5.1 to calculate the mass of dispersant needed to produce a dispersal effectiveness of 0.55 if 5000 kg of oil is spilled into water. Show your working and state the unit. mass of dispersant = … [2] (iv) The scientists stated that a ratio of dispersant to oil of 0.05 is the best ratio to use to scatter oil following an oil spill. Suggest why the scientists stated that this is the best ratio to use. … … … … [2] (c) Wind turbines placed into areas of ocean can provide a renewable source of energy. Discuss the environmental advantages and disadvantages of using wind turbines placed into oceans. … … … … … … … … … … … … … [4] [Total: 17]

17 marks

Mark scheme: 5(a) any 3 from: 3 1 double hulls ; 2 to reduce risk of oil leaks (after collision) / AW ; 3 only wash out hold at special collection sites / AW ; 4 control of sewage release / AW ; 5 control of garbage disposal / AW ; 5(b)(i) 1 linear scales on both axes ; 4 2 axes labelled with units ; 3 plots correct ; 4 straight lines joining points ; 5(b)(ii) (dispersal effectiveness) increases ; 2 levels off, after ratio of 0.10 / from ratio of 0.15 / AW ; 5(b)(iii) 0.05  5000 = 250 ; 2 kg ; 5(b)(iv) any 2 from: 2 1 increasing mass of dispersant has little effect beyond this / AW ; 2 dispersants are toxic / AW ; 3 using less (dispersant) reduces environmental impact / AW ; 4 reduces costs / AW ; 5(c) up to 3 from: 4 1 infinite source of energy / not used up / will not run out / AW ; 2 reduces reliance on fossil fuel / less oil used / AW ; 3 reduces carbon dioxide release / AW ; 4 less need to transport oil / reduced risk of oil spills / less damage to seabed from drilling ; and up to 3 from: 5 limited number of locations (can be used) / may not be windy / (severe) weather may damage turbines / AW ; 6 (turbines) need cables on seabed / installations damage seabed / AW ; 7 example of how marine life damages by turbines ; 8 conflict with (eco)tourism / AW ; 9 high startup cost/maintenance cost / AW ; max 4

This question in 0697/22 May/June 2025

2 A student investigates the effect of temperature on the solubility of carbon dioxide gas in water. The student uses this method. • Place a bottle of fizzy, carbonated water in a refrigerator at a temperature of 4 °C. • Pour 100 cm3 of the carbonated water into a beaker. • Measure the mass of the beaker and carbonated water. • Place the beaker into a water-bath at a temperature of 5 °C, as shown in Fig. 2.1. • Leave the carbonated water, stirring it occasionally until it stops releasing bubbles of carbon dioxide gas. • Reweigh the beaker and the carbonated water. • Calculate the change in mass. • Repeat the experiment at other temperatures up to 50 °C. beaker thermometer carbonated water with gas bubbles water-bath Fig. 2.1 (a) (i) Name one piece of apparatus that the student can use to measure 100 cm3 of carbonated water. … [1] (ii) Suggest two changes to the student’s method to obtain more accurate results. 1 … … 2 … … [2] (b) Fig. 2.2 shows a graph of the student’s results. temperature of water-bath / °C 0 10 20 30 40 50 0.00 – 0.05 – 0.10 change in – 0.15 mass / g – 0.20 – 0.25 – 0.30 Fig. 2.2 Explain the effect of increasing the temperature on the change in mass shown in Fig. 2.2. … … … … … … [3] (c) Explain why warm water usually lies above cold water in the ocean. … … … … … … [3] [Total: 9]

9 marks

This question in 0697/23 May/June 2025

3 Fig. 3.1 shows an ocean food web. sharks tuna lancetfish mackerel shrimps copepods dinoflagellates Fig. 3.1 (a) (i) Name one primary consumer in the food web shown in Fig. 3.1. … [1] (ii) Draw the longest food chain in the food web shown in Fig. 3.1. [2] (b) Fig. 3.2 shows a dinoflagellate from this ocean food web. X Fig. 3.2 (i) In the space, make a large, accurate drawing of the dinoflagellate shown in Fig. 3.2. Do not draw internal structures of the dinoflagellate. [4] (ii) The magnification of the image in Fig. 3.2 is ×360. Calculate the actual length of the dinoflagellate in Fig. 3.2 along the length of the line labelled X. Give your answer in mm and to two significant figures. Show your working. actual length = … mm [3] (iii) State the kingdom that dinoflagellates belong to. … [1] (iv) All dinoflagellates have two flagella. Give one other main feature of dinoflagellates. … [1] (c) (i) Dinoflagellate blooms can occur at different times of the year. Outline how a Secchi disc can be used to compare population sizes of dinoflagellates. … … … … … … [3] (ii) Suggest one reason why using a Secchi disc does not provide an accurate measure of the population size of dinoflagellates. … … [1] [Total: 16]

16 marks

This question in 0697/23 May/June 2025