Edexcel A Level Biology B
Edexcel A Level Biology B Topic 10: Ecosystems Exam Questions
Free Edexcel A Level Biology B exam questions for Topic 10: Ecosystems, with a mark scheme for every pack. Covers ecosystem structure, energy transfer, productivity, succession, population sampling, human effects on ecosystems, climate change and sustainability.
Topic 10: Ecosystems exam questions
5 question packs of real past exam questions, each with its mark scheme. Do not stop after a few: answer as many as you can without notes, then mark every answer with the mark scheme. The more questions you do, the more quickly you will spot how examiners ask about each idea.
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About Edexcel A Level Biology B Topic 10: Ecosystems
Topic 10 of Edexcel A Level Biology B looks at how ecosystems work and how humans affect them. You learn the terms population, community, habitat, niche and ecosystem, and how biotic and abiotic factors determine distribution and abundance. Energy transfer covers gross and net primary productivity and the efficiency of transfer between trophic levels. Changes in ecosystems include succession from pioneer species to a climax community. Human effects include deforestation, pollution, overfishing and climate change, together with conservation and sustainable management. Expect calculations on productivity and efficiency, questions on sampling methods and evaluation of data on human impact.
What you need to know
- Nature of ecosystems An ecosystem includes all living organisms and the non-living environment. Each species occupies a niche. Populations are limited by biotic factors (competition, predation, disease) and abiotic factors (light, temperature, water).
- Energy transfer GPP is the total energy fixed by producers; NPP = GPP - R. Efficiency = energy transferred / energy available x 100. Energy is lost as heat from respiration and in uneaten or undigested material.
- Sampling Use random quadrats or transects for plants and mark-release-recapture for mobile animals; repeat samples to improve reliability.
- Succession Primary succession begins on bare rock with pioneer species; each stage changes conditions, allowing new species to colonise until a climax community forms.
- Human effects Deforestation, burning fossil fuels and agriculture increase greenhouse gases and reduce biodiversity. Climate change affects species distribution, timing of life cycles and enzyme-controlled processes.
- Sustainability Sustainable management includes fishing quotas, replanting, protected areas and reducing carbon emissions, balanced against economic needs.
Common mistakes in Topic 10: Ecosystems
- Saying energy is recycled in ecosystems; energy flows through, while nutrients are recycled.
- Writing that energy is lost at each trophic level because it is used up; it is lost as heat from respiration and in waste.
- Confusing GPP with NPP.
- Describing a climax community as having no change at all; it is stable but still dynamic.
- Assuming correlation between CO2 and temperature proves causation without discussing other evidence.
Try three Topic 10: Ecosystems exam-style questions
1. Producers have an NPP of 24 000 kJ m-2 yr-1 and herbivores receive 1800 kJ m-2 yr-1. Calculate the efficiency of energy transfer. (2 marks)
Show the mark scheme answer
1800 / 24 000 x 100; = 7.5%.
2. Explain why food chains rarely have more than five trophic levels. (3 marks)
Show the mark scheme answer
Energy is lost at each level as heat from respiration and in faeces and uneaten parts; only a small percentage passes on; too little energy remains to support further levels.
3. Describe the process of primary succession. (4 marks)
Show the mark scheme answer
Pioneer species colonise bare rock; they break down rock and add organic matter when they die, forming soil; new species with greater requirements colonise and outcompete earlier ones; biodiversity increases until a climax community forms.
Topic 10: Ecosystems FAQs
What does Edexcel A Level Biology B Topic 10: Ecosystems cover?
It covers ecosystem structure, energy transfer and productivity, sampling, succession, human effects such as climate change and deforestation, and sustainability.
Which paper is Topic 10 examined in?
At A Level, this topic is assessed in Paper 2 and can also appear in Paper 3, which covers general and practical principles from all topics.
Which calculations do I need for Topic 10?
You need NPP = GPP - R, percentage efficiency of energy transfer and population estimates from mark-release-recapture.
