Total marks: 40 · Duration: 45 minutes
Instructions to candidates
- There are forty questions in this paper. Answer all questions.
- For each question there are four possible answers, A, B, C and D. Choose the one you consider correct.
- Each correct answer scores one mark. No marks are deducted for a wrong answer.
- Any working should be done on rough paper. You may use a calculator.
- Where a question describes a graph, a diagram or an experiment in words, you may find it helpful to sketch it.
- This paper covers the Extended content of the Cambridge IGCSE Biology syllabus.
Paper
Multiple choice (40 marks)
1. The lion is named Panthera leo and the tiger is named Panthera tigris. What do these names show?
A) Lions and tigers are the same species. B) Lions and tigers belong to different genera. C) Lions and tigers are in the same genus but are different species. D) Lions and tigers belong to different kingdoms.
2. Which feature places an animal in the arthropods rather than in the annelids?
A) jointed legs and an exoskeleton B) a body divided into segments C) a moist outer surface D) a body cavity containing organs
3. Which structure is found in plant cells and in bacterial cells, but not in animal cells?
A) nucleus B) mitochondrion C) chloroplast D) cell wall
4. The image of a cell in a drawing is 30 mm long. The actual length of the cell is 0.06 mm. What is the magnification of the drawing?
A) × 50 B) × 500 C) × 5000 D) × 0.002
5. Red blood cells are placed in a concentrated salt solution. What happens to them?
A) They burst, because water enters by osmosis. B) They shrink, because water leaves by osmosis. C) They swell, because salt enters by diffusion. D) They do not change, because their cell walls resist changes in shape.
6. Which process needs energy released by respiration?
A) diffusion of oxygen from the alveoli into the blood B) movement of water into a root hair cell from moist soil C) evaporation of water from the surface of mesophyll cells D) uptake of nitrate ions by root hair cells from soil where they are less concentrated
7. A food solution turns purple when biuret solution is added. It stays blue when heated with Benedict's solution. What does the food contain?
A) protein, but no reducing sugar B) reducing sugar, but no protein C) starch and protein D) fat and reducing sugar
8. In a molecule of DNA, which base pairs with adenine?
A) adenine B) cytosine C) thymine D) guanine
9. The activity of an enzyme rises steadily from 10 °C to 40 °C and then falls sharply above 45 °C. Why does the activity fall above 45 °C?
A) The enzyme and substrate molecules move more slowly. B) All of the substrate has been used up. C) The enzyme becomes able to act on more substrates. D) The shape of the active site changes, so the substrate no longer fits.
10. Why does each enzyme catalyse only one type of reaction?
A) Its active site has a shape complementary to one substrate. B) It is used up after it has catalysed one reaction. C) It can only work at one exact temperature. D) It is made from a single type of amino acid.
11. A plant's rate of photosynthesis rises as light intensity increases, then levels off. At the level part of the curve, raising the carbon dioxide concentration increases the rate again. What was limiting the rate at the level part of the curve?
A) light intensity B) the amount of chlorophyll C) carbon dioxide concentration D) the supply of water
12. Which cells in a leaf contain the most chloroplasts?
A) spongy mesophyll cells B) palisade mesophyll cells C) upper epidermis cells D) xylem vessels
13. A plant is grown in a solution that contains no magnesium ions. Its leaves turn yellow. Why?
A) Magnesium is needed to make chlorophyll. B) Magnesium is needed to make proteins. C) Magnesium is needed to make starch. D) Magnesium is needed to make cellulose cell walls.
14. Which enzyme starts the digestion of protein in the stomach?
A) amylase B) lipase C) maltase D) pepsin
15. How does bile help in the digestion of fats?
A) It contains lipase, which breaks fats into fatty acids and glycerol. B) It lowers the pH of the small intestine to suit lipase. C) It emulsifies fats, increasing their surface area for lipase. D) It absorbs fats directly into the lacteals.
16. Which tissue transports sucrose from the leaves to the roots of a plant?
A) xylem B) phloem C) cortex D) epidermis
17. Which set of conditions gives the highest rate of transpiration?
A) cool, humid and still B) warm, dry and windy C) cool, dry and still D) warm, humid and still
18. Why is the muscular wall of the left ventricle thicker than the wall of the right ventricle?
A) It pumps blood around the whole body, at a higher pressure. B) It pumps blood to the lungs, which are a long way from the heart. C) It receives deoxygenated blood from the vena cava. D) It contains more valves than the right ventricle.
19. Which description fits a vein?
A) a thick, muscular wall and a narrow lumen B) a wall that is only one cell thick C) carries blood away from the heart at high pressure D) a wide lumen and valves that prevent backflow
20. In a mammal, blood passes through the heart twice for each complete circuit of the body. What is an advantage of this?
A) Blood flows more slowly to the organs, so it can deliver more glucose. B) Less oxygen is needed by the body's tissues. C) Blood returning from the lungs can be pumped at high pressure to the body. D) Oxygenated and deoxygenated blood can mix in the heart.
21. A person is vaccinated against measles. Why are they protected if they meet the measles virus later?
A) Memory cells quickly produce large numbers of specific antibodies. B) The antibiotics in the vaccine remain in the blood for life. C) The vaccine kills every measles virus that enters the body permanently. D) The antigens from the vaccine stay on the surface of red blood cells.
22. How is cholera mainly transmitted?
A) in droplets breathed out by an infected person B) through direct contact with the skin of an infected person C) by the bite of an infected mosquito D) in water contaminated with faeces
23. Which feature of the alveoli increases the rate of diffusion of gases?
A) thick walls containing cartilage B) a small number of blood capillaries C) a large surface area and walls one cell thick D) a dry inner surface
24. What happens when a person breathes in?
A) The diaphragm relaxes and moves upwards. B) The external intercostal muscles contract and the ribs move up and out. C) The volume of the thorax decreases. D) The pressure in the lungs rises above atmospheric pressure.
25. What are the products of anaerobic respiration in yeast?
A) lactic acid only B) lactic acid and carbon dioxide C) ethanol only D) ethanol and carbon dioxide
26. After a sprint, a runner keeps breathing deeply and quickly for several minutes. Why?
A) to supply oxygen to break down the lactic acid that built up in the muscles B) to remove extra glucose from the blood C) to cool the lungs after exercise D) to replace the water lost in sweat
27. Which substance is filtered out of the blood in the kidney but is normally completely reabsorbed?
A) urea B) glucose C) protein D) red blood cells
28. Which sequence shows the pathway of an impulse in a reflex arc?
A) receptor → motor neurone → relay neurone → sensory neurone → effector B) effector → sensory neurone → relay neurone → motor neurone → receptor C) receptor → sensory neurone → relay neurone → motor neurone → effector D) sensory neurone → receptor → relay neurone → effector → motor neurone
29. A person walks from a dark room into bright sunlight. What happens in the iris?
A) The circular muscles relax and the pupil widens. B) The circular muscles contract and the pupil narrows. C) The radial muscles contract and the pupil narrows. D) The ciliary muscles contract and the pupil widens.
30. What happens after a person eats a meal rich in carbohydrate?
A) Glucagon is secreted, and the liver converts glycogen to glucose. B) Adrenaline is secreted, and the heart rate rises. C) Insulin is secreted, and the liver releases glucose into the blood. D) Insulin is secreted, and the liver converts glucose to glycogen.
31. A plant shoot lit from one side bends towards the light. Why?
A) Auxin collects on the shaded side, so cells there elongate more. B) Auxin collects on the lit side, so cells there elongate more. C) Light kills cells on the shaded side, so the shoot bends. D) Auxin moves down to the roots, so the shoot stops growing on one side.
32. Why are antibiotics not used to treat diseases caused by viruses?
A) Viruses are too large for antibiotics to reach them. B) Viruses are always resistant to every antibiotic. C) Viruses lack the structures that antibiotics act on, and reproduce inside host cells. D) Antibiotics only work inside the digestive system.
33. What is the function of the pollen tube?
A) to attract insects to the flower B) to store food for the developing seed C) to protect the ovule from drying out D) to carry the male nucleus to the ovule
34. Where does fertilisation normally take place in a human?
A) uterus B) oviduct C) ovary D) cervix
35. In pea plants, the allele for tall stems (T) is dominant to the allele for short stems (t). A plant with genotype Tt is crossed with a plant with genotype tt. What proportion of the offspring are expected to be short?
A) 0% B) 25% C) 50% D) 75%
36. How many chromosomes are in a human sperm cell?
A) 23 B) 46 C) 22 D) 92
37. Red-green colour blindness is caused by a recessive allele on the X chromosome. A woman who is a carrier has children with a man who has normal colour vision. What is the probability that one of their sons is colour blind?
A) 0% B) 25% C) 100% D) 50%
38. A population of bacteria becomes resistant to an antibiotic over many generations. What is the explanation?
A) The antibiotic causes mutations that make the bacteria resistant. B) Resistant bacteria survive and reproduce, passing on the allele for resistance. C) The bacteria learn to avoid the antibiotic. D) The antibiotic becomes weaker the more often it is used.
39. In a food chain, the producers contain 20 000 kJ of energy and the primary consumers contain 2000 kJ. What percentage of the energy is transferred to the primary consumers?
A) 10% B) 1% C) 20% D) 90%
40. Bacteria are genetically modified to make human insulin. Which enzyme is used to cut open the bacterial plasmid?
A) DNA ligase B) amylase C) a restriction enzyme D) protease