OCR GCSE Biology A: Ecosystem organisation, abiotic and biotic factors, trophic levels and biomass transfer (J247) – 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 statements B4.1e to B4.1j of OCR GCSE (9-1) Gateway Science Biology A (J247), Version 4.0 (August 2026), first assessment in 2018. None of the statements is Higher Tier only. Read the study guide first if you need to, or use the revision notes. Course links: OCR GCSE Biology hub, printable checklist and free diagnostics.

Questions

1. A reed bed beside a river contains 200 reed warblers, many other bird, insect and plant species, microorganisms, water and mud. State the level of organisation of each of the following. (a) The 200 reed warblers. [1] (b) All the living things in the reed bed. [1] (c) The living things together with the water, mud and light. [1]

2. Classify each factor as abiotic or biotic. (a) Soil pH. (b) A hawk hunting in a field. (c) The amount of rain. (d) The number of aphids on a rose bush. [4]

3. A student measured the mean number of sorrel plants per square metre on four soils.

Soil pH	4.5	5.5	6.5	7.5
Mean plants per m²	14.2	9.6	4.1	1.2

(a) Describe the pattern shown by the data. [2] (b) Suggest why soil pH can affect where plants grow. [1] (c) State one other abiotic factor that could differ between the soils and affect the results. [1]

4. Name the type of relationship in each case and state who benefits. (a) Bacteria live in the root nodules of clover and fix nitrogen. [2] (b) A tick feeds on blood from a deer. [2] (c) A kestrel catches a field vole. [1]

5. Bean seedlings were sown very close together in a tray. After four weeks they were shorter and had fewer leaves than seedlings sown far apart. (a) Name two resources the dense seedlings competed for. [2] (b) Explain why the dense seedlings grew less. [2]

6. The table shows counts of two species in a hedge over six months.

Month	Weevils per plant	Birds per 100 m
1	55	3
2	150	4
3	240	8
4	120	15
5	45	7
6	30	4

(a) Identify the predator and give the evidence. [2] (b) Explain why weevil numbers fell between months 3 and 5. [2] (c) Explain why bird numbers also fell after month 4. [1]

7. Food chain: seaweed → limpet → crab → gull. (a) Name the producer. [1] (b) Name the secondary consumer. [1] (c) Explain why seaweed is called a producer. [1] (d) State what the arrows show. [1]

8. A sheep eats 80 kg dry mass of grass. 24 kg is egested, 40 kg is lost through respiration, 4 kg is lost as excretory waste and the rest becomes sheep tissue. (a) Calculate the mass that becomes sheep tissue. [1] (b) Calculate the percentage of the grass lost through respiration. [1] (c) Explain how egestion, excretion and respiration each cause biomass loss. [3] (d) Explain why a pyramid of biomass is always narrower at the top. [1]

9. Dry mass per square metre of a meadow: grass 1200 g, grasshoppers 150 g, shrews 12.6 g. (a) Calculate the grasshopper biomass as a percentage of the grass biomass. [1] (b) Calculate the shrew biomass as a percentage of the grasshopper biomass. Give your answer to 2 significant figures. [1] (c) Describe how you would draw the pyramid of biomass. [2] (d) Explain why dry mass is used. [1]

10. In a marine food chain the biomass produced in one year (kg per km²) is phytoplankton 5400, zooplankton 594, herring 62.5 and tuna 5.0. (a) Calculate the efficiency of transfer from zooplankton to herring. Give your answer to 3 significant figures. [2] (b) Calculate the efficiency of transfer from herring to tuna. [1] (c) Calculate the overall efficiency from phytoplankton to tuna. Give your answer to 2 significant figures. [2] (d) Explain why the overall efficiency is much lower than each separate transfer. [1]

11. A farmer grows 7500 kg of grain on a field. Fed to cattle, 9% of the grain biomass becomes beef. (a) Calculate the mass of beef produced. [1] (b) A food chain starts with 80 000 kg of producer biomass and 10% is transferred at each step. Calculate the biomass at the fourth trophic level. [2] (c) Use your answer to explain why food chains rarely have more than five trophic levels. [2] (d) Explain why more people can be fed from a field of grain if the grain is eaten directly. [3]

Answers

1. (a) Population [1]. (b) Community [1]. (c) Ecosystem [1]. [3] Examiner insight: A community contains living things only, so answers that include the water and mud under “community” lose the mark.

2. (a) Abiotic [1]. (b) Biotic [1]. (c) Abiotic [1]. (d) Biotic [1]. [4] Examiner insight: Rain is a non-living factor even though it affects living things, and the aphid count is biotic because it comes from living organisms.

3. (a) As soil pH rises from 4.5 to 7.5 the mean number of sorrel plants falls [1], from 14.2 to 1.2 per m² [1]. (b) pH affects the availability of minerals or damages roots, so some plants cannot grow [1]. (c) Moisture, or temperature, or light intensity [1]. [4] Examiner insight: Quoting figures from the table is what turns “it decreases” into a complete description of a trend.

4. (a) Mutualism [1]; both the bacteria and the clover benefit [1]. (b) Parasitism [1]; the tick benefits and the deer is harmed [1]. (c) Predation [1]. [5] Examiner insight: Naming the relationship is rarely enough on its own; state who gains and who is harmed.

5. (a) Light [1] and water or mineral ions or space [1]. (b) The seedlings shaded each other and shared limited water and minerals [1], so each made less food by photosynthesis and grew less [1]. [4] Examiner insight: Link the lack of a resource to its use in the plant, here photosynthesis, rather than writing that the plants “did not get enough”.

6. (a) The birds are the predator [1] because their peak in month 4 follows the weevil peak in month 3 [1]. (b) More birds were eating the weevils [1] so fewer survived [1]. (c) Fewer weevils meant less food, so some birds starved or left [1]. [5] Examiner insight: The delay between the two peaks is the evidence for which species is the predator, and a stated time lag strengthens the answer.

7. (a) Seaweed [1]. (b) Crab [1]. (c) It makes its own food by photosynthesis [1]. (d) The direction in which biomass is transferred, from the food to the feeder [1]. [4] Examiner insight: An arrow does not mean “eats”; say it shows the transfer of biomass towards the eater.

8. (a) 80 - 24 - 40 - 4 = 12 kg [1]. (b) 40 / 80 × 100 = 50% [1]. (c) Egestion: undigested material such as cellulose leaves in faeces [1]. Excretion: waste such as urea is removed [1]. Respiration: glucose is broken down so carbon is lost as carbon dioxide [1]. (d) Biomass is lost at each transfer, so less is available at each higher level [1]. [6] Examiner insight: A calculation answer with no unit or percent sign is incomplete, and each loss route needs its own mechanism.

9. (a) 150 / 1200 × 100 = 12.5% [1]. (b) 12.6 / 150 × 100 = 8.4% [1]. (c) Draw horizontal bars to a chosen scale, with grass at the base [1], each bar centred on a vertical line and labelled with the organism [1]. (d) Water content varies, so dry mass shows the actual mass of tissue [1]. [5] Examiner insight: “To scale” and “grass at the bottom” are the two details a description of a pyramid must contain.

10. (a) 62.5 / 594 × 100 [1] = 10.5% [1]. (b) 5.0 / 62.5 × 100 = 8.0% [1]. (c) 5.0 / 5400 × 100 [1] = 0.093% [1]. (d) Biomass is lost at every step, so the losses add up across the chain [1]. [6] Examiner insight: The producer level is the denominator in an overall efficiency, and answers that divide by the tuna value are a common slip.

11. (a) 7500 × 0.09 = 675 kg [1]. (b) Level 2: 8000 kg, level 3: 800 kg [1], level 4: 80 kg [1]. (c) By level 5 only 8 kg remains, and by level 6 only 0.8 kg [1], which is too little to support a population large enough to survive [1]. (d) Eating grain directly removes one trophic level [1], so the losses from egestion, excretion and respiration in cattle are avoided [1], and more of the grain biomass reaches humans [1]. [8] Examiner insight: Strong answers name the losses and say that there is one fewer transfer, rather than only stating that plants are “more efficient”.

Where marks are usually lost

• Mixing up population and community, or leaving abiotic parts out of the ecosystem.
• Describing a trend without figures from the table.
• Naming a relationship without saying who benefits.
• Writing that a resource “ran out” without linking it to photosynthesis or growth.
• Drawing arrows from predator to prey.
• Forgetting a % sign or unit.
• Dividing by the wrong trophic level in an efficiency calculation.
• Calling egestion excretion.
• Giving “energy is lost” with no named route of biomass loss.

Next steps

• Review the revision notes and the study guide.
• Visit the OCR GCSE Biology hub and the printable checklist.
• Take one of the free 10-minute diagnostics.
• Book a free trial class.

Official syllabus

OCR GCSE (9-1) Gateway Science Biology A (J247), Version 4.0 (August 2026), first assessment 2018, published by OCR. Topic B4.1, statements e to j.