3 The diagram shows an elm tree. (a) Elm trees may be infected by a fungus that causes a disease. State two characteristics of a fungus. 1 … 2 … [2] (b) The fungus moves through an infected tree inside the xylem vessels. The tree responds to stop the movement of the fungus by producing substances that block the xylem vessels. This causes the leaves of the tree to wilt and to become yellow. Explain how the response of the tree to infection leads to these symptoms of disease. … … … … … … … … … … [5] (c) An insect called the elm bark beetle is the vector of this disease. Describe what is meant by the term vector. … … … … [2] (d) Elm trees can reproduce when the roots from one parent tree spread out near the surface of the soil. This is shown in the diagram below. roots of parent tree grow stems called suckers each sucker forms a new tree (i) Name the type of reproduction shown in the diagram. … [1] (ii) Suggest why this type of reproduction makes it difficult to control the spread of the disease caused by the fungus. … … … … … … [3] [Total: 13]

3(a) 1 hyphae / mycelium ; 2 saprotrophic / saprophytic / feeds on dead matter AW / decomposer ; 3 spores ; 4 cell wall + chitin ; 5 more than one nucleus / multinucleate ; 2 3(b) 1 less / no + water transported / water absorbed / transpiration ; 2 water loss greater than water uptake ; 3 less + water in cells ; 4 flaccid / loss of turgor / plasmolysed ; 5 magnesium / Mg ; 6 less / no + chlorophyll ; 5 3(c) 1 transfer / carries / spreads AW + pathogen / fungus / parasite ; 2 one organism AW to another ; 3 not itself + affected / infected ; 2 3(d)(i) asexual ; 1 3(d)(ii) 1 close together ; 2 connected AW ; 3 genetically identical / all genetically susceptible / clones ; 3

8 (a) Define the term drug. … … … … … … [3] (b) Describe the possible effects of abuse of a named drug. … … … … … … … … … … … … … [7] [Total: 10]

8(a) externally administered / taken ; chemical / substance ; modifies / affects / alters AW + metabolism / chemical reactions in the body ; 3 8(b) named drug ; 1 any six from … reason for taking it ; tolerance / increased dosage for same effect ; dependence / addiction ; withdrawal ; crime / drink driving ; funding the habit / financial implications ; social effects, e.g. effect on family / social acceptability ; any two adverse effects on health of addict from drug / means of taking it ;; Max 6 6 9(a) aerobic + respiration ; energy released AW ; germination / radicle / plumule ; 3 9(b) water potential gradient AW ; intake + by osmosis / diffusion ; root hair ; turgor ; prevents wilting AW ; reactant / use in AW + photosynthesis ; transpiration ; cooling effect on plant ; solvent / dissolved ; sucrose / amino acids + in phloem ; mineral ions or named + in xylem ; 7

9 Describe the large-scale production of a named antibiotic and explain the importance of each stage of the process. … … … … … … … … … … … … … … … … … … … … [Total: 10]

9 1 named antibiotic ; 1 if marking point 1 awarded, marking point 2 must be correctly linked any nine from … 2 fungus / bacterium / correct named ; 3 fermenter ; 4 sterilised / steam + to prevent contamination AW ; 5 carbohydrate (or named) + respiration / energy ; 6 protein / amino acids + growth ; 7 paddles / impeller / stirring + reason for stirring ; 8 oxygen / air + aerobic ; 9 sparger / bubbles + increased surface area ; 10 control temperature / reference to temp. between 25–45 °C ; 11 removal of CO2 / pH control / ref. a pH between 5–8 ; 12 temperature / pH + enzymes ; 13 maximum / increased + growth ; 14 extraction / filtration / purification / crystallisation ; 9

3 The photograph shows an insect called a leafhopper. When it feeds, its mouthparts penetrate the xylem of the plant on which it lives. Leafhoppers carry disease-causing bacteria from plant to plant. (a) (i) State the term used for a disease-causing organism. … [1] (ii) State the term used for an animal, such as an insect, that carries disease-causing organisms. … [1] (b) The bacteria carried by the leafhopper reproduce inside the plant stem and block the xylem. (i) Suggest and explain why this can cause the leaves of the plant to wilt. … … … … [4] (ii) The leaves of plants affected by these bacteria may also develop white patches. Suggest reasons for this. … … … [2] (iii) Suggest an explanation for the fact that the fruits of plants affected by these bacteria are small and poorly developed. … … … … … [4] [Total: 12]

3(a)(i) pathogen ; 1 3(a)(ii) vector ; 1 3(b)(i) water lost from leaves ; by evaporation / transpiration ; cannot be replaced / cannot pass up stem ; water lost from cells ; lose their turgor / turgidity ; 4 3(b)(ii) can’t make chlorophyll ; reference to magnesium / zinc not getting to leaves ; 2 3(b)(iii) reduced photosynthesis ; less sugar / starch / protein made ; less water available to fruit ; fewer nutrients or named nutrient sent to fruit ; less growth or development (linked to protein) ; 4 To score marks, you must correctly identify 'pathogen' for a disease-causing organism and 'vector' for an animal that carries disease. For wilting, explain that water is lost from leaves by transpiration but cannot be replaced due to blocked xylem, causing cells to lose turgor. For white patches, suggest that chlorophyll cannot be made, possibly due to a lack of magnesium or zinc reaching the leaves.

25 What are the effects of drinking a large quantity of alcohol on the human body? effects on the body acts as a reaction time damages the A depressant decreases kidney B depressant increases liver C stimulant increases kidney D stimulant decreases liver

Answer: B To earn the mark, a student must correctly identify that alcohol acts as a depressant, increases reaction time, and damages the liver.

Cambridge O Level Biology · 5090

O-Level Biology (5090) Disease and immunity past paper questions

Revise O-Level Biology (5090) — Disease and immunity with real Cambridge past-paper questions grouped by topic, each shown with its marking scheme. Working one topic at a time targets exactly the skill each question tests.

71 free questions from 2017–2021, each with its marking scheme. Open the full topical bank to filter by subtopic, paper, and year.

Disease and immunity in O-Level Biology 5090 exams, 2020–2025

Across 2020–2025, Disease and immunity accounted for 97 questions worth 379 marks in Cambridge O Level Biology (5090) papers.

By year
Year	Questions	Marks
2020	17	64
2021	11	41
2022	14	54
2023	22	92
2024	17	52
2025	16	76

Most-tested subtopics

12.1 Disease222 marks
12.3 Immunity125 marks
12.2 Antibiotics78 marks

Appears in

Paper 1 · 70 qs
Paper 2 · 25 qs
Paper 3 · 1 q
Paper 4 · 1 q

All most-tested Biology topics

2021 May/Jun · Paper 2 · Q3 · 13 marks
Marking scheme
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2021 Oct/Nov · Paper 2 · Q8 · 10 marks
Marking scheme
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2021 May/Jun · Paper 2 · Q9 · 10 marks
Marking scheme
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2020 May/Jun · Paper 2 · Q3 · 12 marks
Marking scheme
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2021 May/Jun · Paper 1 · Q25 · 1 mark
Marking scheme
Mark scheme — 2021 Paper 1 Q25
Answer: B
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