10 free IGCSE Biology Ecology & Human Influence questions written in the style of Cambridge Biology papers: 3 multiple-choice and 7 structured, each with its answer and mark scheme. 4 of them are A* challenge questions, built to catch the mistakes strong students still make.
This topic covers Food chains, webs & energy flow, Nutrient cycles, Populations, Food supply, Habitat destruction, Pollution, Conservation. Work through the questions below, then generate a full Ecology & Human Influence paper with a fresh set every time.
Generate a full Ecology & Human Influence paper →Which sequence describes eutrophication after fertiliser runs into a lake?
Answer: C
Producers in a food chain capture 60000 kJ/m² per year. 10% of this energy is passed to primary consumers and 8% of the energy in primary consumers is passed to secondary consumers.
How much energy reaches the secondary consumers?
Answer: A
What is the original source of energy for most food chains?
Answer: A
Fish stocks can be overexploited.
Describe two ways of making fishing sustainable.
Explain why a larger mesh size helps conserve fish stocks.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | quotas; net size; closed seasons Any 2 of: quotas; larger net mesh size; closed seasons/protected areas; restocking B2 | 2 |
| (b) | young fish escape and breed young/small fish can escape B1 they survive to reproduce B1 | 2 |
Excess fertiliser can run into rivers and cause eutrophication.
Describe the sequence of events in eutrophication.
Suggest one way farmers can reduce eutrophication.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | nitrates → algal growth → light blocked → plants die → decomposers use oxygen → fish die fertiliser (nitrate) runs into water B1 algae grow rapidly (algal bloom) B1 algae block light so plants below die B1 decomposers break down dead plants and use up oxygen B1 fish and other organisms die from lack of oxygen B1 | 5 |
| (b) | apply fertiliser carefully; buffer strips use less fertiliser / not before rain / leave strips of land by rivers B1 | 1 |
This question is about nutrient cycles.
Name the process that removes carbon dioxide from the air and the processes that return it.
Explain the role of decomposers in the carbon cycle.
Explain why waterlogged soils lead to a build-up of dead plant material.
Describe the roles of nitrogen-fixing, nitrifying and denitrifying bacteria in the nitrogen cycle.
Explain why plants need nitrate ions.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | photosynthesis; respiration; combustion; decomposition photosynthesis removes CO₂ B1 respiration and decomposition return it B1 combustion of fossil fuels returns it B1 | 3 |
| (b) | break down dead organic matter; respire, releasing CO₂ decomposers (bacteria and fungi) break down dead organisms and waste B1 they respire, releasing carbon dioxide B1 | 2 |
| (c) | lack of oxygen; decomposers cannot respire aerobically waterlogged soil lacks oxygen B1 so decomposers cannot respire aerobically and decomposition is slow B1 | 2 |
| (d) | fixing: N₂ to nitrogen compounds (ammonium); nitrifying: ammonium to nitrates; denitrifying: nitrates to N₂ nitrogen-fixing bacteria convert nitrogen gas into ammonium compounds (in root nodules) B1 nitrifying bacteria convert ammonium ions to nitrates B1 denitrifying bacteria convert nitrates back into nitrogen gas B1 | 3 |
| (e) | to make amino acids / proteins to make amino acids (proteins) B1 | 1 |
The size of a population is affected by several factors.
Define a population.
State three factors that affect the rate of population growth.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | group of same species in same area Any 1 of: a group of organisms of one species; living in the same area at the same time B1 | 1 |
| (b) | food supply; predation; disease; competition food supply B1 predation B1 disease (competition, space) B1 | 3 |
Untreated sewage enters a river at a point 0 m. Samples are taken upstream and at distances downstream. Table 8.1 shows the results.
| distance from sewage outlet / m | 100 upstream | 50 | 200 | 400 | 800 | 1500 |
|---|---|---|---|---|---|---|
| dissolved oxygen / mg per dm³ | 9.2 | 4.4 | 2.2 | 3.8 | 7.2 | 8.8 |
| number of invertebrate species | 15 | 5 | 2 | 5 | 10 | 14 |
Calculate the percentage decrease in dissolved oxygen between 100 m upstream and 200 m downstream.
Explain why the concentration of dissolved oxygen falls downstream of the sewage outlet.
Suggest why the dissolved oxygen concentration rises again further downstream.
Describe the relationship between dissolved oxygen and the number of invertebrate species.
Some species, such as sludge worms, are found only where dissolved oxygen is low. Explain how such species can be used to monitor pollution.
Fertiliser running into a lake can have a similar effect. Describe the sequence of events that follows.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | 76.1 % (9.2 − 2.2) ÷ 9.2 × 100 C1 76.1 % A1 | 2 |
| (b) | bacteria decompose sewage; respire aerobically; use oxygen sewage provides organic matter / food for bacteria B1 bacteria (decomposers) increase in number B1 their aerobic respiration uses dissolved oxygen B1 | 3 |
| (c) | sewage broken down; fewer bacteria; oxygen dissolves from air / photosynthesis most of the sewage has been decomposed so fewer bacteria / less respiration B1 oxygen dissolves from the air / is released by photosynthesis of plants and algae B1 | 2 |
| (d) | more oxygen, more species the higher the dissolved oxygen concentration, the more invertebrate species (positive correlation) B1 | 1 |
| (e) | indicator species; presence shows low oxygen / pollution they are indicator species B1 their presence (and absence of sensitive species) shows that the water is polluted / low in oxygen B1 | 2 |
| (f) | algal bloom; light blocked, plants die; decomposers increase; oxygen used, animals die nitrate / phosphate causes rapid growth of algae (algal bloom) B1 algae block light so plants below die B1 decomposers / bacteria increase and decompose dead plants B1 their respiration uses oxygen so fish and other animals die (eutrophication) B1 | 4 |
A sigmoid growth curve describes a population of rabbits introduced to an island.
Explain why the population grows slowly at first.
Explain why the population stops growing.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | few individuals reproducing few rabbits to reproduce B1 | 1 |
| (b) | limiting factors: food, predators, disease Any 2 of: limited food/space; increased predation/disease; births equal deaths B2 | 2 |
Water is recycled in the water cycle.
Describe the processes that return water to the atmosphere.
Describe how water vapour becomes rain.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | evaporation; transpiration evaporation (from sea/land) B1 transpiration from plants B1 | 2 |
| (b) | condenses into clouds, precipitation water vapour cools and condenses to form clouds B1 precipitation as rain B1 | 2 |
In the 0610 syllabus, Ecology & Human Influence covers Food chains, webs & energy flow, Nutrient cycles, Populations, Food supply, Habitat destruction, Pollution, Conservation.
This page has 10 Ecology & Human Influence questions with answers. For more, the free generator on mentorriyaz.in builds a new Ecology & Human Influence paper with a full mark scheme each time you click.
Riyaz Shaikh has mentored IGCSE, IB and A Level students for 15+ years, one-on-one, online and in Mumbai. The hardest questions on this site are the ones he uses to find a student's weak points.
Meet Riyaz →Original Cambridge-style practice questions written for mentorriyaz.in. These are not Cambridge past paper questions, and this site is not affiliated with or endorsed by Cambridge University Press & Assessment. Updated 2026-11-04. Paper generator · mentorriyaz.in