OxfordAQA International GCSE Biology: Energy transfer, biomass pyramids, adaptations and competition (9201) – Practice Questions

These are original questions written for Marlbridge, for revision and practice on this content. They are not reproduced past-paper questions, and they do not replicate the exam’s exact structure, question count or mark tariffs – examination boards hold copyright in their own papers. Use these alongside the official past papers from your board or school.

These questions cover OxfordAQA International GCSE Biology, Version 5.2 (for exams May/June 2018 onwards), sections 3.3.1 and 3.3.2. Teaching is in the study guide and the revision notes. Course hub: OxfordAQA IGCSE Biology. Checklist: printable checklist. Questions 5 and 11 include content marked B in the specification.

Questions

1. State two reasons why only about 10% of the biomass of one trophic level is transferred to the next. [2]

2. The table shows the biomass in part of the ocean.

Group	Biomass (kg per hectare)
Phytoplankton	2 400
Zooplankton	290
Small fish	31

(a) Calculate the percentage of biomass transferred from phytoplankton to zooplankton. Give your answer to 3 significant figures. [2] (b) Calculate the percentage transferred from zooplankton to small fish. Give your answer to 3 significant figures. [2] (c) Large fish eat the small fish. Predict their biomass if the transfer is 10%. [1]

3. Seagrass bed biomass (dry mass, g per m²): seagrass 1 600, snails 180, crabs 24.

(a) Use a scale of 1 mm = 20 g to calculate the length of each bar of a pyramid of biomass. [3] (b) State two features of a correctly drawn pyramid of biomass. [2]

4. A wheat field receives 4.0 × 10⁶ kJ of light energy per m² in a year.

(a) Wheat transfers about 1% of the incident energy. Calculate the energy stored. [2] (b) Cattle eat the wheat and about 10% is transferred to them. Calculate the energy transferred to the cattle. [2]

5. (B) A hectare of crop stores 9 000 MJ of edible energy. One person needs 12 MJ per day.

(a) Calculate how many person-days of food the crop provides if people eat it directly. [2] (b) The crop is fed to pigs instead, and 10% of its energy ends up in the meat. Calculate how many person-days the meat provides. [2] (c) Explain why shortening a food chain improves the efficiency of food production. [2]

6. In a woodland the biomass per hectare is: leaves 12 000 kg, caterpillars 1 300 kg, small birds 150 kg, hawks 14 kg.

(a) Calculate the percentage transferred from caterpillars to small birds, to 3 significant figures. [2] (b) Use the data to explain why a fifth trophic level is unlikely in this woodland. [2]

7. Seedlings of one species were grown in trays at different densities. The mean dry mass per plant was measured after four weeks.

Seedlings per tray	Mean dry mass per plant (g)
15	1.20
30	0.82
60	0.45
120	0.24

(a) Describe the trend shown. [2] (b) Calculate the total dry mass per tray at 60 and at 120 seedlings. [2] (c) Calculate the percentage decrease in mean mass per plant from 15 to 120 seedlings. [1] (d) Explain the results, naming two resources. [2]

8. Male birds of one species defend an area of woodland against other males.

(a) State three things that animals compete for. [3] (b) Suggest one benefit to a bird that holds a large area. [1]

9. A lizard lives on hot desert sand. It is pale and sandy coloured, has long legs that hold its body above the sand, lifts its feet alternately off the sand when standing, and buries itself in the sand at midday. It gets most of its water from the insects it eats. Suggest four ways in which the lizard is adapted to its environment. [4]

10. (a) Classify each as structural, behavioural or functional: (i) a bird flies to warmer lands for the winter; (ii) a desert plant has thick, fleshy stems that store water; (iii) a mammal produces a very small volume of concentrated urine. [3] (b) Some bacteria live in a lake where salt levels are far higher than in the sea. What name is given to organisms living in such conditions? [1] (c) Suggest why most organisms could not survive in the lake. [2]

11. (B) Explain how each parasite is adapted to its way of life. (a) A flea living among the hair of a mammal. [2] (b) A tapeworm living in the small intestine of a mammal. [4] (c) A malaria parasite, a single-celled organism that infects humans. [2]

Answers

1. Any two from: some materials and energy are lost in waste materials (faeces, urine) [1]; respiration supplies the energy for living processes such as movement, and much of this is transferred to the surroundings [1]; some parts (for example bones) are not eaten (a third valid idea, but only two marks are available). [2] Examiner insight: answers gain credit for two distinct reasons; repeating “energy is lost” in two ways is one idea, so name waste and respiration separately.

2. (a) 290 ÷ 2 400 × 100 [1] = 12.1% [1] (b) 31 ÷ 290 × 100 [1] = 10.7% [1] (c) 31 × 0.10 = 3.1 kg per hectare [1] Examiner insight: show the division and the multiplication by 100 so the method is visible, and round only at the end; a rounded early value can change the last figure.

3. (a) Seagrass: 1 600 ÷ 20 = 80 mm [1]; snails: 180 ÷ 20 = 9 mm [1]; crabs: 24 ÷ 20 = 1.2 mm [1] (b) Any two: bars drawn to scale with seagrass at the base [1]; bars the same height and centred on a vertical line [1]; labelled with units and the scale used (only two marks are available). [2] Examiner insight: give each bar as a length with units; a bare number without mm is easy to misread, and the producer must be at the base.

4. (a) 4.0 × 10⁶ × 0.01 [1] = 4.0 × 10⁴ kJ per m² [1] (b) 4.0 × 10⁴ × 0.10 [1] = 4.0 × 10³ kJ per m² [1] Examiner insight: in standard form questions, keep the power of ten and the units; answers such as 4 000 without units lose clarity.

5. (a) 9 000 ÷ 12 [1] = 750 person-days [1] (b) Energy in meat = 9 000 × 0.10 = 900 MJ [1]; 900 ÷ 12 = 75 person-days [1] (c) Each stage loses much biomass and energy in waste and respiration [1]; fewer stages means a greater proportion of the producers’ energy reaches humans [1] Examiner insight: “explain” answers need the reason as well as the statement; say what is lost at each stage, not just that fewer stages is better.

6. (a) 150 ÷ 1 300 × 100 [1] = 11.5% [1] (b) About 10% of 14 kg is only about 1.4 kg [1]; too little biomass to support a population of a further consumer [1] Examiner insight: use a figure from the data in the second part; a general statement about energy loss without a number from the table is weaker.

7. (a) Mean mass per plant decreases as density increases [1]; for example from 1.20 g at 15 seedlings to 0.24 g at 120 seedlings [1] (b) 60 × 0.45 = 27.0 g [1]; 120 × 0.24 = 28.8 g [1] (c) (1.20 − 0.24) ÷ 1.20 × 100 = 80.0% [1] (d) Seedlings compete for light, water or mineral ions (any two named) [1]; each plant gets a smaller share, so grows less [1] Examiner insight: “describe” needs the trend and data quoted from the table; “explain” needs a named resource that is in short supply, not just “competition”.

8. (a) Food [1]; mates [1]; territory [1] (b) More food (or more nesting sites) for the bird and its young [1] Examiner insight: keep resources matched to the organism; animals compete for food, mates and territory, not for light.

9. Any four from the following: pale sandy colour gives camouflage from predators [1]; long legs lift the body away from hot sand [1]; lifting feet alternately reduces heat gain from the sand [1]; burying at midday avoids the hottest temperatures and reduces water loss [1]; getting water from its food means it does not need to find drinking water (a fifth valid idea, but only four marks are available). [4] Examiner insight: each mark needs the feature plus how it helps; “it has long legs” alone does not show an advantage.

10. (a) (i) behavioural [1]; (ii) structural [1]; (iii) functional [1] (b) Extremophiles [1] (c) The salt concentration is so high that water would leave the cells of most organisms [1], so their cells could not function (they would die) [1] Examiner insight: in “suggest” questions a sensible reasoned idea earns credit; link the extreme condition to the effect on cells.

11. (a) Body flattened from side to side so it moves easily between hairs [1]; claws grip hair (or piercing mouthparts feed on blood) [1] (b) Hooks or suckers on the head attach to the gut wall [1]; thick outer covering resists digestive enzymes [1]; long flat body gives a large surface area to absorb digested food from the host [1]; produces many eggs, so some offspring reach new hosts [1] (c) Very small, so it can live inside liver and red blood cells [1]; reproduces rapidly there, and a mosquito carries it between hosts [1] Examiner insight: join each feature to its function (attach, resist, absorb, spread); lists of features without a purpose are limited.

Where marks are usually lost

• Giving a percentage without showing the division and the multiplication by 100.
• Dividing the lower level by the higher level.
• Leaving out units (kg per hectare, kJ per m², mm).
• Drawing pyramid bars with different heights or no scale.
• Saying energy is “used up” rather than transferred to the surroundings.
• Writing “competition” without naming the resource.
• Naming a feature without saying how it helps survival.
• Giving one general parasite statement (“it is adapted to live in the gut”) with no feature.

Next steps

• Revise with the revision notes and re-read the study guide.
• Course hub: OxfordAQA IGCSE Biology; printable checklist.
• Try all free 10-minute diagnostics.
• Book a free trial class.

Official syllabus

OxfordAQA International GCSE Biology (9201), Version 5.2, for exams May/June 2018 onwards, published by OxfordAQA. Sections 3.3.1 and 3.3.2.