Practise 50 real questions on Ecology and human influences from 2021 to 2026. See the answer and explanation as soon as you answer.
Ecology and human influences is one of the 13 main topics in our O Level Biology (Cambridge (CAIE) 5090) question bank, and about 9% of its real questions come from it. Tayyari Karo has 50 real questions on this topic from 2021 to 2026, from Paper 1, Paper 2, Paper 3, Paper 4; 36 are multiple choice and marked instantly, and the rest are structured questions with a model answer. By difficulty: 41 medium, 6 easy, 3 hard.
Work through the questions below, then open the explanation for each one. Redo the ones you missed a few days later.
These are real past-paper questions. Think of your answer first, then open the explanation.
What is an aim of conservationists within the fishing industry?
Answer: B. to ensure that enough adult fish mature to breed each year
Sustainable fishing requires enough fish to reach breeding age to maintain stocks.
What is a method of conserving fish stocks?
Answer: C. having closed fishing seasons
Students studied decay of leaves in bags of mesh sizes 0.1, 1.0 and 5.0 mm over 5 months. The larger the mesh, the greater the percentage loss in mass. What can they conclude?
Answer: B. The larger the mesh size the faster the rate of decay.
Drainage from nitrogen-fertiliser fields can result in fish dying in rivers.
Which sequence of events describes what happens?
Answer: D. more growth of water plants → more plant decomposition by bacteria → less oxygen dissolved
Fertiliser → algal/plant growth → decomposition by bacteria uses O2 → fish die.
What increases in the long term as a result of tropical deforestation?
Answer: C. soil erosion
Which statements are correct? 1 Energy cannot be recycled in food webs. 2 Producers make their own organic nutrients. 3 The Sun is the principal source of energy input to biological systems.
Answer: A. 1, 2 and 3
7 (a) Describe how carbon is cycled between living organisms and the atmosphere. [5]
(b) Compare the effects of three woodland management methods: burned; removed and made into objects; left in the ecosystem. [5]
(a) CO2 in the atmosphere is absorbed by plants and converted to carbohydrates by photosynthesis; these make other organic substances or are eaten by animals; respiration by organisms releases CO2 back to the atmosphere. [any 5]
(b) Burning: releases CO2 (greenhouse gas/global warming). Made into objects: locks up carbon (store) but removes tree from ecosystem. Left: decomposed by fungi/bacteria returning nutrients to soil and releasing CO2 gradually; dead wood gives habitat. [compare, max 5]
Carbon moves between atmosphere and organisms via photosynthesis and respiration.
Farmers spread artificial nitrogen-containing fertiliser. (a) Describe how nitrogen from the fertiliser passes from soil to become part of the food humans eat. (b) Discuss the advantages and disadvantages of artificial nitrogen fertilisers.
(a) Fertiliser adds ammonium/nitrates/urea to soil; nitrifying bacteria form nitrates; root hairs absorb them by active transport; transported in xylem; used to make amino acids/proteins; humans eat the plants/animals. (b) Advantages: replaces nitrogen removed by crops, improves growth/yield, feeds growing population. Disadvantages: energy to produce/transport; monoculture, degraded soil, leaching -> eutrophication/algal bloom, bacteria use oxygen, killing water organisms.
| Session | Paper 1 | Paper 2 | Paper 3 | Paper 4 |
|---|---|---|---|---|
| May/June 2026 | 2 | 2 | – | – |
| May/June 2025 | 2 | 1 | – | – |
| Oct/Nov 2025 | 3 | – | – | – |
| May/June 2024 | 4 | – | 1 | – |
| Oct/Nov 2024 | 4 | 1 | – | – |
| May/June 2023 | 4 | 2 | – | – |
| Oct/Nov 2023 | 4 | 1 | – | – |
| May/June 2022 | 3 | 1 | – | – |
| Oct/Nov 2022 | 2 | – | 1 | 1 |
| May/June 2021 | 4 | 2 | – | – |
| Oct/Nov 2021 | 4 | 1 | – | – |
50 real O Level Biology (5090) questions on Ecology and human influences from 2021 to 2026, from Paper 1, Paper 2, Paper 3, Paper 4. Each one shows the year, session and paper it came from.
Yes. Every question shows the correct answer and a short explanation the moment you answer.
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