Organisms and their environment

1. INTERACTIVE MULTIPLE CHOICE QUESTIONS Organisms and their environment The answers are provided. Explanations of why the alternatives are unsatisfactory are also offered

2. These multiple choice questions are similar to the ones set by the GCSE and IGCSE Examination Boards except that, in some cases, there may be more than one acceptable answer For this reason, even if you select a correct answer at your first attempt, it is worth looking at all the alternatives (a) to see if there is a better answer and (b) to see why some of the alternatives are unacceptable Question 1

3. Question 1 A thrush, a snail, a cabbage and a sparrow hawk are all part of a food chain. Which of them is a primary (or ‘first order’) consumer? (a) The cabbage (b) The snail (c) The sparrow hawk (d) The thrush Question 2

4. No The cabbage is the producer at the beginning of the food chain

5. Yes The snail is the primary (first order) consumer. It eats the cabbage leaves

6. No The sparrow hawk is a tertiary (‘third order’) consumer at the end of the food chain. It is a predator of the thrush

7. No The thrush is the secondary (‘second order’) consumer. It eats the snail and is itself eaten by the sparrow hawk

8. Question 2 In the nitrogen cycle, the bacteria in root nodules of leguminous plants can convert atmospheric nitrogen into nitrates. These bacteria are called … (a) nitrifying bacteria (b) denitrifying bacteria (c) nitrite bacteria (d) nitrogen-fixing bacteria Question 3

9. No Although the bacteria in root nodules ultimately increase the nitrogen content of the soil, the term ‘nitrifyingbacteria’ applies mainly to bacteria living freely in the soil. These bacteria cannot use atmospheric nitrogen.

10. No Denitrifying bacteria convert the nitrates in the soil into atmospheric nitrogen.

11. No Nitrite bacteria live freely in the soil and convert ammonium ions into nitrates. They cannot use atmospheric nitrogen

12. Yes The nitrogen-fixing bacteria (Rhizobium spp) live mainly in root nodules of leguminous plants. They convert nitrogen (from the air in the soil) into nitrates, which are eventually incorporated into amino acids by the plant.

13. Question 3 sunlight CONSUMERS The diagram represents a natural recycling process die eaten die A PRODUCERS What is missing at A? minerals and salts decay (a) Animals SOIL (b) Plants (c) Decomposers (d) Bacteria Question 4

14. No Animals are the consumers

15. No Plants are the producers

16. Yes The decomposers, (mainly bacteria and fungi) break down the dead remains of organisms and release their products into the soil

17. No Some bacteria are important decomposers, but there are many species of bacteria which are not decomposers. Also, there are many fungi which play a part in decay.

18. Question 4 In a food chain, the amount of energy passed from one trophic level to the next …. (a) increases (b) decreases (c) stays the same (d) sometimes increases; sometimes decreases Question 5

19. No The organisms at any trophic level will be using part of their resources to produce energy, so there will be less to pass to the next level

20. Yes The organisms at any trophic level will be using part of their resources to produce energy, so there will be less to pass to the next level

21. No The organisms at any trophic level will be using part of their resources to produce energy, so there will be less to pass to the next level

22. No The amount of energy passed from one trophic level to the next may vary but there is always a decrease

23. Question 5 C population The graph shows the sigmoid curve for population growth. At C … B (a) the death rate exceeds the reproduction rate (b) the reproduction rate exceeds the death rate A (c) the death rate and repro-duction rates are the same time (d) the death rate and repro-duction rate decrease equally Question 6

24. No If the death rate exceeds the reproduction rate, the population will decrease

25. No If the reproduction rate exceeds the death rate, the population will continue to grow

26. Yes If organisms die at the same rate as they are created, the population will be stable

27. Yes If fewer organisms are created, but the death rate decreases at the same rate, the population will stay the same but the point of stability will be reached at a lower population level

28. Question 6 What is the source of energy on which nearly all living organisms ultimately depend? (a) Photosynthesis (b) Respiration (c) Combustion (d) Sunlight Question 7

29. No Nearly all living organisms depend directly or indirectly on photosynthesis by plants for their energy supply. But this is not the ultimate source of energy

30. No Respiration is the way in which most living organisms derive energy from their food but it is not the ultimate source of energy

31. No Combustion is a source of energy for many processes but not for living organisms

32. Yes The process of photosynthesis in green plants uses energy from sunlight for making food. The energy from this food is used by nearly all living organisms either by eating plants or eating each other

33. Question 7 Which of the following gases are the cause of acid rain? (a) Carbon dioxide (b) Carbon monoxide (c) Nitrogen oxide (d) Sulphur dioxide Question 8

34. No Carbon dioxide does dissolve in rain to form a weak solution of carbonic acid (H2CO3) but this is normal and does not contribute to what is known as ‘acid rain’. However, it is thought to be making the ocean more acid and this is a cause for concern

35. No Carbon monoxide is a poisonous gas but does not contribute to acid rain

36. Yes Oxides of nitrogen dissolve in rain water to form nitric acid which is very harmful to lakes and land plants

37. Yes Sulphur dioxide dissolves in water to form, eventually, sulphuric acid. This damages lakes and land plants

38. Question 8 Acute shortage of oxygen in lakes and rivers is caused by … (a) eutrophication (b) the oxygen demand by the excess of decaying plant material (c) excess nitrate and phosphate (d) excessive growth of algae Question 9

39. No Eutrophication refers to a high level of nutrients in a body of water. It may cause excessive algal growth but is not a direct cause of oxygen depletion

40. Yes The oxygen demand of an excess of decomposing plant material, e.g. algae, is the immediate cause of the reduction in the oxygen content of the water in lakes and rivers. The excess of plant material is the result of eutrophication

41. No Eutrophication results from high levels of nitrate and phosphate in the water. But although this encourages excessive algal growth it does not inevitably lead to oxygen depletion.

42. No The excessive growth of algae is not itself a cause of oxygen depletion.

43. Question 9 Which of the following processes make no net contribution of carbon dioxide to the Earth’s atmosphere? (a) Growing crops (b) Burning wood (c) Burning coal (d) Raising cattle Question 10

44. Yes The growing crops are photosynthesising and removing carbon dioxide from the atmosphere.

45. Yes The carbon in wood comes from the carbon dioxide absorbed by the tree in the course of photosynthesis. When the wood is burned, the amount of carbon dioxide released is the same as that taken in by photosynthesis

46. No The carbon in coal comes from trees which were fossilized about 300 million years ago. So the carbon dioxide released from burning coal adds to the present day carbon dioxide in the atmosphere

47. No Respiration in cattle produces carbon dioxide which is added to the atmosphere

48. Question 10 For the conservation of animals, the most important step is… (a) reduction in the use of pesticides (b) preservation of habitat (c) suppression of hunting (d) captive breeding programmes

49. No Reduction in the use of pesticides certainly helps to conserve, for example, insect species and the organisms which feed on them (e.g. birds) but it affects only a limited range of animals

50. Yes This is the most important step. If an animal’s habitat is destroyed, it is unlikely to survive