2 A person visits an eye doctor to have an eye test. On the wall of the doctor’s room is a diagram of an eye. X layer Y choroid layer contains melanin in its cells (a) (i) Name the part labelled X. … [1] (ii) Describe one way in which the structure of X is related to its function. … … … [2] (iii) Name layer Y. … [1] (b) As part of the eye test, the doctor shines a bright light into the eye and takes a picture. The picture shows layer Y and the choroid layer behind it. Z blood vessels in choroid layer blind spot (i) Name structure Z. … [1] (ii) Layer Y does not contain blood vessels. Explain how the blood vessels in the choroid layer are important for layer Y. … … … … … … [4] (c) When the bright light is shone into the eye there is a pupil reflex which causes the pupil to become smaller. Explain how named parts of the eye and of the nervous system are involved in this pupil reflex. … … … … … … [4] (d) Some people inherit a condition which prevents the production of the dark pigment melanin in their choroid and skin cells. The gene involved has two alleles, A (dominant) and a (recessive). Only people with two recessive alleles have this condition. Two people, each with a heterozygous genotype, have children together. (i) Complete the genetic diagram to show the possible genotypes and phenotypes of the children. genotypes of parents gametes possible genotypes of children … … × … … … … possible phenotypes of children … … … … … … … … [4] (ii) State the probability of these two people having a child who does not produce melanin. … [1] [Total: 18]

2(a)(i) lens ; 1 2(a)(ii) any two from: transparent / spherical / curved sides ; allows light to pass through / to focus / refract light ; or flexible / elastic / can change shape AW ; accommodation / focus objects ; 2 1 mark for structural feature and 1 mark for function 2(a)(iii) retina ; 1 2(b)(i) macula / yellow spot / fovea ; 1 2(b)(ii) any four from: bring glucose / amino acids / minerals / vitamins ; for energy / repair of cells ; bring oxygen ; for (aerobic) respiration ; take urea / carbon dioxide away ; diffusion ; capillaries / veins / arteries mentioned in correct context ; bring white blood cells ; to fight infection ; 4 2(c) any four from: retina / rods detect extra light (intensity) ; impulse + to CNS / brain ; via optic nerve / sensory neurone ; back to eye / iris / effector / muscle + motor neurone ; radial muscles relax ; circular muscles contract ; iris becomes bigger / elongates ; reflex arc ; 4 2(d)(i) parental genotypes = Aa + Aa ; gametes a and A ; offspring genotypes AA, Aa, Aa and aa ; correctly linked phenotypes: AA & Aa = produce melanin, aa don’t produce melanin ; 4 2(d)(ii) 25% / ¼ / 0.25 / I in 4 / 1:3 ; 1

3 A man is cooking in a hot kitchen and sweat is being released by sweat glands in his skin. (a) (i) Explain the term homeostasis with reference to sweating. … … … … [2] (ii) Explain how receptors and blood vessels in the man’s skin are also involved in homeostasis when he is in the hot kitchen. … … … … … … [4] (b) Sweat contains very small quantities of the waste product urea. State the name of the organ where most urea is made in the body. … [1] (c) The table shows the concentrations of some chemicals found in the sweat, urine and blood plasma of a healthy human. chemical concentration of chemical / mmol per dm3 sweat urine blood plasma urea 22 393 6 sodium 66 110 141 chloride 59 103 99 (i) Use the data in the table to compare the chemical composition of urine and blood plasma. … … … … … … [4] (ii) A patient has kidney disease and is about to start dialysis treatment. Suggest and explain the concentration of urea in the sweat of the patient compared to that of a person who does not have kidney disease. … … … … [3] [Total: 14]

3(a)(i) any two from: (homeostasis is) the maintenance of a constant ; internal environment / temperature ; return to norm / return to set-point / negative feedback ; evaporation of sweat removes heat / thermal energy / cools / decreases temperature ; 2 3(a)(ii) any four from: receptors + detection of temperature ; impulse to brain / CNS ; vasodilation ; arterioles / blood vessels widen ; increase in blood + near skin surface ; greater + loss of heat / thermal energy ; by radiation ; 4 3(b) liver ; 1 3(c)(i) any four from: less urea in blood plasma ; more sodium in blood plasma ; less chloride in blood plasma ; comparative data quote with units ; data manipulation, e.g. 50 × higher urea in urine than blood plasma ; 4 3(c)(ii) high(er) / over 22 (in patient) ; reduced filtration / reduced removal of urea (from kidney) ; reference to blood plasma ; 3

4 The diagram shows part of the human alimentary canal and its associated organs. H F … … … (a) Complete the three labels on the diagram by naming the structures. [3] (b) Describe the functions of the structure labelled F. … … … … [3] (c) Name structure H and describe its role in homeostasis. name … role … … … [2] [Total: 8]

4(a) clockwise from top: oesophagus / gullet ; duodenum / small intestine ; gall bladder ; 3 R ileum 4(b) any three from: digestion / break down food or protein / protein to polypeptides / protein to amino acids ; (mechanical) muscle / contractions / movement + make food particles smaller / chyme ; (chemical) enzymes / proteases / pepsin + proteins ; hydrochloric acid + optimum pH AW ; hydrochloric acid + destroy microbes / defence against microbes ; mucus + protects lining / lubrication ; 3 4(c) pancreas ; control of blood glucose concentration / level or produces / releases + insulin / glucagon ; 2

4 A study investigated the probability of pregnancy resulting from sexual intercourse on specific days of the menstrual cycle. The graph shows the results of this study. 5 0 10 20 30 40 50 4 3 days before ovulation percentage probability of pregnancy 2 1 ovulation (a) (i) The study shows a probability of 20% that sexual intercourse three days before ovulation will result in pregnancy. State how many times more likely pregnancy is if sexual intercourse takes place two days later. … [1] (ii) Explain the role of named hormones in the menstrual cycle during the days investigated by this study. … … … … … … … … [5] (b) The diagram shows a fetus developing in the uterus of a pregnant female human. structure X Name structure X and describe the functions of this structure. name … functions … … … … … [3] [Total: 9]

4(a)(i) 2 / twice as likely / doubles ; 1 4(a)(ii) FSH ; (only if FSH stated) growth / maturation + of follicle ; (only if FSH stated) in ovary ; oestrogen ; (only if oestrogen stated) repair AW of uterus + wall / lining ; LH ; (only if LH stated) ovulation AW ; 5 4(b) placenta ; 1 any two from … diffusion ; oxygen / glucose / antibodies + from mother / to fetus AW ; carbon dioxide / urea + from fetus AW / to mother ; from blood + to blood ; produces progesterone ; 2

Cambridge O Level Biology · 5090

O-Level Biology (5090) Coordination and control past paper questions

Revise O-Level Biology (5090) — Coordination and control 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.

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

Coordination and control in O-Level Biology 5090 exams, 2020–2025

Across 2020–2025, Coordination and control accounted for 153 questions worth 505 marks in Cambridge O Level Biology (5090) papers.

By year
Year	Questions	Marks
2020	25	85
2021	28	90
2022	26	64
2023	27	118
2024	21	60
2025	26	88

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Paper 1 · 115 qs
Paper 2 · 33 qs
Paper 3 · 2 qs
Paper 4 · 3 qs

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2021 May/Jun · Paper 2 · Q2 · 18 marks
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2021 Oct/Nov · Paper 2 · Q3 · 14 marks
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2021 May/Jun · Paper 2 · Q4 · 8 marks
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2021 Oct/Nov · Paper 2 · Q4 · 9 marks
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2021 May/Jun · Paper 1 · Q20 · 1 mark
Marking scheme
Mark scheme — 2021 Paper 1 Q20
Answer: A
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