WJEC A Level Biology
WJEC A Level Biology 3.5 Population Size and Ecosystems Exam Questions
Free WJEC A Level Biology exam questions on 3.5 Population Size and Ecosystems, with mark schemes. Covers population growth, limiting factors, energy flow, productivity, succession and nutrient cycles.
3.5 Population Size and Ecosystems exam questions
1 question pack of real past exam questions with its mark scheme. Answer every question without notes, then mark your answers line by line against the mark scheme.
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WJEC A Level Biology Flashcards (Anki & Quizlet)
Every answer is written in mark scheme wording, so you learn exactly what examiners give marks for. Use them on Anki or Quizlet, then test yourself with the questions on this page.
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About WJEC A Level Biology 3.5 Population Size and Ecosystems
This topic covers how populations change and how energy and nutrients move through ecosystems.
What you need to know
- Population growth Lag, log, stationary and death phases; carrying capacity; density-dependent and independent factors.
- Energy flow Energy transfer between trophic levels, GPP and NPP, and efficiency calculations.
- Succession Primary and secondary succession towards a climax community.
- Nutrient cycles The carbon and nitrogen cycles, including nitrogen fixation, nitrification and denitrification.
Common mistakes in 3.5 Population Size and Ecosystems
- Saying energy is recycled.
- Mixing up nitrification and denitrification.
- Confusing GPP and NPP.
Try three 3.5 Population Size and Ecosystems exam-style questions
1. Explain why a population stops growing at carrying capacity. (2 marks)
Show the mark scheme answer
Limiting factors such as food or space (1) mean birth rate equals death rate (1).
2. Describe the role of nitrifying bacteria. (2 marks)
Show the mark scheme answer
They convert ammonium ions to nitrites (1) and then nitrates, which plants can absorb (1).
3. Calculate the efficiency of energy transfer if 2,000 kJ reaches primary consumers and 150 kJ reaches secondary consumers. (1 mark)
Show the mark scheme answer
150 / 2000 x 100 = 7.5 percent.
3.5 Population Size and Ecosystems FAQs
What does Population Size and Ecosystems cover?
Population growth, energy transfer, succession and the carbon and nitrogen cycles.
Which practical links here?
Sampling techniques such as quadrats and mark-release-recapture.
What is a density-dependent factor?
A factor whose effect increases as population density rises, such as disease or competition.
Revise this topic with flashcards: WJEC A Level Biology Flashcards, with mark scheme answers for Anki and Quizlet.
