Cambridge IGCSE Marine Science (Maldives only) 0697 — 2025 May/June Paper 2 · Variant 1

1 Fig. 1.1 shows shrimps on sale at a fish market. 5 cm Fig. 1.1 (a) Shrimps are crustaceans. State two main characteristic features of crustaceans. 1 ................................................................................................................................................ 2 ................................................................................................................................................ [2] (b) Shrimps are a source of essential nutrients such as lipids. (i) Name one other major nutrient group that is needed by animals. ..................................................................................................................................... [1] (ii) Describe a method to test a sample of shrimp for the presence of lipids. ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ..................................................................................................................................... [3] (iii) Explain the importance of lipids in the diet of animals. ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ..................................................................................................................................... [2] [Total: 8]

Mark scheme: Question Answer Marks 1(a) any 2 from: 2 1 bilateral symmetry ; 2 exoskeleton ; 3 compound eyes ; 4 two pairs of antennae ; 5 abdominal segments with jointed legs ; 1(b)(i) protein / carbohydrates / vitamins / minerals ; 1 1(b)(ii) any 3 from: 3 1 grind up the sample / AW ; 2 add alcohol / ethanol ; 3 stir / mix / shake / AW ; 4 add water AND, white / emulsion, forms ; 1(b)(iii) any 2 from: 2 insulation ; energy ; lipids contain vitamins ; AVP ;

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]

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;

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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]

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 ;

4 Fig. 4.1 shows the structure of the Earth with the core and the crust labelled. crust A core Fig. 4.1 (a) (i) Name the section labelled A in Fig. 4.1. ..................................................................................................................................... [1] (ii) Describe the structure of the Earth’s core shown in Fig. 4.1. ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ..................................................................................................................................... [2] (b) The spinning of the Earth and prevailing winds are two factors that cause oceanic currents. (i) State what is meant by the term oceanic current. ........................................................................................................................................... ..................................................................................................................................... [1] (ii) State one other factor that causes oceanic currents. ........................................................................................................................................... ..................................................................................................................................... [1] (c) A student investigates how wind speed and wind direction affect the speed of an oceanic current. The student measures the mean speed of the current, the wind speed and the wind direction each day for five days. Fig. 4.2 shows the results in the student’s notebook. Day 1 Day 4 Mean current speed: 5 m/s Mean current speed: 5 m/s Wind speed: 15 m/s Wind speed: 25 m/s Wind direction: from NW Wind direction: from SW Day 2 Day 5 Wind direction: from NW Mean current speed: 2 m/s Wind speed: 20 m/s Wind direction: from SE Mean current speed: 8 m/s Wind speed: 25 m/s Day 3 Wind direction: from NW Wind speed: 5 m/s Mean current speed: 2 m/s Fig. 4.2 (i) Complete Table 4.1 to show the student’s results from Fig. 4.2. Write the data in order of increasing day number. Table 4.1 day number [3] (ii) Name an independent variable measured by the student in the investigation. ..................................................................................................................................... [1] (iii) The student releases an orange float from a boat into the water to measure the current speed. Describe the measurements and calculations the student needs to make to determine the mean current speed. ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ..................................................................................................................................... [3] (iv) The student concludes that increasing prevailing wind speed increases the current speed. Discuss whether the student’s data in Fig. 4.2 supports this conclusion. ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ..................................................................................................................................... [3] [Total: 15]

Mark scheme: 4(a)(i) mantle ; 1 4(a)(ii) any 2 from: 2 1 made of iron ; 2 inner (core) is solid ; 3 outer (core) is, liquid / molten ; 4(b)(i) (continuous) movement of water in a direction / AW ; 1 4(b)(ii) tides / density / temperature (difference) / salinity (difference) ; 1 4(c)(i) headings with units ; 3 data in order of day ; data correctly placed in table ; 4(c)(ii) wind speed / wind direction ; 1 4(c)(iii) any 3 from: 3 measure distance moved by float / AW ; measure time taken for float to move / AW ; calculate speed as distance  time ; repeats to calculate mean ; 4(c)(iv) any 3 from: 3 1 (supported as) (mean) current speed increases with wind speed when wind is from NW / on days 1, 2 and 3 / AW ; 2 prevailing wind is from NW / AW ; 3 on Day 4 wind speed, is higher than Day 1 but (mean) current speed is, same / AW ; 4 on Day 5 wind speed, is higher than Day 1 / Day 2, but (mean) current speed is lower / AW ; 5 on Day 4 and Day 5 wind speeds are same but (mean) current speeds are different / AW ; 6 wind direction affects (mean) current speed / AW ; 7 few data points with each wind direction / need more repeats / low sample size / AW ;

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]

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

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6 Female leatherback turtles lay eggs in nests on sandy shores. Fig. 6.1 shows eggs in a turtle nest. Fig. 6.1 (a) Explain the role of migration in the life cycle of the leatherback turtle. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ............................................................................................................................................. [3] (b) The temperature of the nest that eggs are laid in affects the sex of the offspring produced. Fig. 6.2 shows the effect of temperature on the percentage of eggs that develop into female turtles. 100 90 80 70 60 percentage of eggs that 50 develop into female turtles 40 30 20 10 0 27 28 29 30 31 temperature of nest / °C Fig. 6.2 (i) Use Fig. 6.2 to determine the percentage of eggs that develop into female turtles from a nest at a temperature of 30 °C. percentage = .............................. % [1] (ii) Use your answer in (b)(i) to calculate the number of male turtles and of female turtles that will hatch from 500 eggs placed at a temperature of 30 °C. Show your working. number of male turtles = .............................. number of female turtles = .............................. [2] (iii) Explain why increased combustion of fossil fuels can reduce the populations of turtles. Use Fig. 6.2 and your answer in (b)(ii) to support your answer. ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ..................................................................................................................................... [3]

Mark scheme: 6(a) any 3 from: 3 1 young / hatchlings / after hatching, move to, (open) ocean / sea ; 2 move to feeding grounds / feed whilst at sea / AW ; 3 idea of reduced competition for food / AW ; 4 go to areas with fewer predators / avoid predation / AW ; 5 move using ocean currents / AW ; 6 become sexually mature at sea / find mates (when in water) / AW ; 7 (females) return to sandy shores (to lay eggs) / females return to shores where they hatched / AW ; 6(b)(i) 91 (%) ; 1 6(b)(ii) (male =) 45 ; 2 (female =) 455 ; 6(b)(iii) any 3 from: 3 1 increased carbon dioxide / AW ; 2 increased temperature / AW ; 3 fewer males / more females / AW ; 4 less breeding / less mating / reduced reproduction / AW ; 5 AVP ; 6(c) any 6 from: 6 1 use shores with different profiles / slopes / angles / AW ; 2 place poles at top and bottom of area of shore / AW ; 3 measure distance (between poles) / AW ; 4 measure angle with clinometer / AW ; 5 count nests (on shore) / determine nest numbers / AW ; 6 use of quadrats / use of a transect (to sample area) / AW ; 7 same time (of day) / season / time of year / AW ; 8 same light intensity / same noise levels / AW ; 9 idea of suitable safety measure/feature ; 10 idea of ethical issue ;

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