O Level Biology 5090 · Topic 19

Topic 19: past paper questions

178 real questionsasked in 10 of the last 10 exam series2019–2025usually: Suggest, Explain, Describe, State, Complete

Real questions on topic 19

The newest 20 of 71 written questions, plus 107 multiple-choice. Open one to see it on the real paper.

5090/21 · October/November 2025 · Q6a[2]
Describe what is meant by a sustainable resource.
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5090/22 · October/November 2025 · Q3c(ii)[3]
Explain why removing carbon from the atmosphere may help the global environment.
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5090/22 · October/November 2025 · Q3d[3]
Different species of Azolla are found naturally in many countries. Azolla has also been introduced by humans to some countries where it is not native. When Azolla is introduced to a country, it can have an impact on natural fresh water ecosystems. Suggest how Azolla can have an impact on these fresh water ecosystems.
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5090/21 · May/June 2025 · Q2a(i)[1]
State the source of energy for this food web.
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5090/21 · May/June 2025 · Q2a(ii)[2]
Complete Table 2.1 by writing the number of different organisms in this food web that fit each description. The first one has been done for you. Table 2.1 description producers 2 secondary consumers carnivores number of different organisms
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5090/21 · May/June 2025 · Q2a(iii)[2]
The hawk feeds at two different trophic levels. Use Fig. 2.1 to explain this statement.
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5090/21 · May/June 2025 · Q5a[3]
Explain how the increasing concentration of carbon dioxide in the atmosphere is causing global warming.
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5090/22 · May/June 2025 · Q2d[3]
If humans reduce the amount of animal protein they eat, then less agricultural land is required. Suggest three environmental benefits of reducing the amount of land used for agriculture.
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5090/21 · October/November 2024 · Q4c[2]
Explain the effect of an increasing concentration of carbon dioxide in the atmosphere.
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5090/22 · October/November 2024 · Q5a[2]
Describe what is meant by the term sustainable resource.
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5090/22 · October/November 2024 · Q5b(i)[4]
Using the information from Fig. 5.1, describe the trend in quota size and suggest explanations for this trend.
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5090/22 · October/November 2024 · Q5b(ii)[4]
Setting fishing quotas is one method used when trying to conserve fish stocks. Explain how two other named methods can be used to conserve fish stocks. name of method explanation name of method explanation
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5090/22 · May/June 2024 · Q7a[2]
The total mass of plastics produced globally in the year 2020 was 367 million tonnes. It is estimated that 3% of all plastics produced globally each year enters the ocean as plastic pollution. Calculate the total mass of plastic pollution that is estimated to have entered the ocean during the year 2020. Space for worki...
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5090/22 · May/June 2024 · Q7b(i)[2]
Some packaging is made from biodegradable carbohydrates. Microorganisms break down larger carbohydrate molecules into smaller molecules. Identify this process and name one type of microorganism that is involved.
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5090/22 · May/June 2024 · Q7b(ii)[7]
Most plastics that enter ecosystems as pollution are non-biodegradable. Describe the harmful effects of non-biodegradable plastics on both aquatic and terrestrial ecosystems.
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5090/22 · October/November 2023 · Q2a[4]
Construct a food web to show the flow of energy between organisms in this ecosystem.
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5090/22 · October/November 2023 · Q7a(i)[2]
ecosystem
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5090/22 · October/November 2023 · Q7a(ii)[1]
biodiversity
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5090/22 · October/November 2023 · Q7a(iii)[2]
species
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5090/22 · October/November 2023 · Q7b[5]
Like many forests around the world, mangrove forests are vulnerable to the effects of human activity. Explain how forests can be conserved as a sustainable resource.
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What examiners said

Candidates were provided with a blank space to construct a food web from the information supplied. They were expected to include all six named organisms in the web and to link them correctly with arrows that showed the flow of energy from one organism to the next. Perhaps it was the mention of energy rather than feeding relationships that caused some candidates to stumble on this question and atte...
— Examiner report, October/November 2023, 5090/22 Q2(a) (Cambridge)

Candidates could generally access one of the two marks available for defining an ecosystem either by explaining that ecosystems comprise biotic and abiotic factors or by explaining that the biotic factors interact with each other. Some candidates had learned the syllabus definition and were able to score both marks.
— Examiner report, October/November 2023, 5090/22 Q7(a)(i) (Cambridge)

This was the lowest scoring question on the paper. It was extremely rare for a candidate to recall the exact definition of biodiversity. Many gave answers that attempted to cover the ‘bio’and ‘diversity’ parts of the word and these answers were generally too vague in nature to score.
— Examiner report, October/November 2023, 5090/22 Q7(a)(ii) (Cambridge)

Practise this topic

Answer these questions online and get each one marked against the official mark scheme, with what you missed and how to fix it.

Practise topic 19

In the syllabus

19.1 Energy flow

Understand that the Sun is the principal source of energy input to most biological systems
Explain why most forms of life are completely dependent on photosynthesis
Describe the flow of energy through food chains and webs including energy from light and energy in living organisms and its eventual transfer to the environment
Construct and interpret simple food chains
Understand the terms producer, consumer, herbivore, carnivore and decomposer
Describe food webs as networks of interconnected food chains and construct and interpret them
Explain why the transfer of energy from one trophic level to another is inefficient
Explain why food chains usually have fewer than five trophic levels
Explain why it is more energy efficient for humans to eat crop plants than to eat livestock that have been fed on crop plants
Construct and interpret pyramids of numbers, biomass and energy

19.2 Nutrient cycles

Describe the carbon cycle, limited to: photosynthesis, respiration, feeding, decomposition, formation of fossil fuels and combustion
Outline the nitrogen cycle in making nitrogen available for plant and animal protein, limited to: (a) decomposition of plant and animal protein to ammonium ions (b) nitrification (c) nitrogen fixation by lightning and bacteria (d) absorption of nitrate ions by plants (e) production of amino acids and protein (f) feeding and digestion of proteins (g) denitrification (the names of individual bacteria are not required)
Outline the role of fungi and bacteria in decomposition

19.3 Ecosystems and biodiversity

Describe a population as a group of organisms of one species, living in the same area, at the same time
Describe a community as all of the populations of different species in an ecosystem
Describe an ecosystem as a unit containing the community of organisms and their environment, interacting together
Describe biodiversity as the number of different species that live in an area
Identify and state the factors affecting the rate of population growth for a population of an organism, limited to: food supply, competition, predation and disease
Understand that the growth of the human population is increasing the demand for global resources

19.4 Effects of humans on ecosystems

Outline the causes and describe the consequences of deforestation, limited to its effects on: biodiversity, extinction, loss of soil, flooding and concentration of carbon dioxide in the atmosphere
Describe the impacts humans have through: (a) over-harvesting of plant and animal species (b) introducing a non-native species to an ecosystem
Describe the harmful effects of: (a) water pollution by untreated sewage and nitrogen-containing fertilisers leading to eutrophication, limited to: (i) increased availability of nitrate and other ions (ii) increased growth of producers (iii) increased decomposition after death of producers (iv) increased aerobic respiration by decomposers (v) reduction in dissolved oxygen (vi) death of organisms requiring dissolved oxygen in water (b) air pollution by greenhouse gases (carbon dioxide and methane), contributing to global warming and its likely effects (c) pollution due to insecticides and herbicides (d) non-biodegradable plastics in the environment, in both aquatic and terrestrial ecosystems

19.5 Conservation

Discuss reasons for conservation of species with reference to: (a) maintenance of biodiversity (b) reducing extinction (c) protecting vulnerable environments
Explain how forests can be conserved using education, protected areas, quotas and replanting
Explain how fish stocks can be conserved using education, closed seasons, protected areas, controlled net types and mesh size, quotas and monitoring
Describe a sustainable resource as one which is produced as rapidly as it is removed from the environment so that it does not run out

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