Pollution — Paper 2 · IGCSE Biology (9-1) 0970

39 Deforestation can have a negative impact on the environment. Which statement about the negative impact of deforestation is correct? A decreases the levels of carbon dioxide which can lead to reduced rates of photosynthesis B decreases the amount of water flowing in local rivers so there is less flooding C leads to soil loss so there is less fertile soil for the growth of crops in the area D provides less land for the extraction of natural resources

1 marks

Answer: C

This question in 0970/21 May/June 2018

40 When nitrates enter a lake they cause rapid growth of algae on the surface of the water. This causes the following changes in the lake: 1 a decrease in the concentration of dissolved oxygen in the water 2 fish and other aquatic animals die 3 an increase in aerobic respiration by decomposers 4 producers die and decomposition increases In which order do these changes occur? A 1 → 2 → 4 → 3 B 3 → 1 → 2 → 4 C 4 → 2 → 3 → 1 D 4 → 3 → 1 → 2

1 marks

Answer: D

This question in 0970/21 May/June 2018

39 The statements describe some of the events that occur during eutrophication. What is directly responsible for the increase in bacteria? A a decrease in dissolved oxygen concentration B an increase in nitrate concentration C an increase in the population of algae D an increase in the death of producers

1 marks

Answer: D

This question in 0970/22 Oct/Nov 2018

40 Large areas of tropical forests have been cleared to grow monocultures of palm oil plants. Which effect will this have on the ecosystem? A The use of fossil fuels in the area will decrease. B The use of pesticides in the area will decrease. C The variety of species in the area will decrease. D The variety of species in the area will increase.

1 marks

Answer: C

This question in 0970/21 May/June 2019

36 The diagram shows how sewage is treated. air out second settling aeration screen settling water to river tank tank tank sludge air in sludge sludge sludge disposal digester Why is air bubbled through the aeration tank? A to encourage microorganisms to reproduce quickly B to float the sludge C to settle the sludge D to stop microorganisms from reproducing too quickly

1 marks

Answer: A

This question in 0970/22 May/June 2019

39 Evidence shows that some aquatic organisms have been feminised. What is the most likely cause of this? A increased nitrates running off farmland into the rivers B female hormones excreted by women taking contraceptive pills C infectious diseases in the fish D decreasing levels of oxygen in the rivers

1 marks

Answer: B

This question in 0970/22 May/June 2019

39 What are the possible effects of deforestation? decrease in atmospheric loss of soil flooding carbon dioxide A yes yes no B yes no yes C no yes no D no no yes

1 marks

Answer: A

This question in 0970/22 Oct/Nov 2019

40 The bloodworm is an organism that is found in heavily polluted water. The diagram shows where raw sewage flows into a river. Where would there be fewest bloodworms? input of raw sewage A D B C direction of flow

1 marks

Answer: A

This question in 0970/22 Oct/Nov 2019

40 When a river is polluted by fertiliser, the following processes may occur. 1 increased aerobic respiration of decomposers 2 increased growth of producers 3 decreased oxygen concentration in the water What is the correct sequence for these processes? A 1 → 2 → 3 B 1 → 3 → 2 C 2 → 1 → 3 D 2 → 3 → 1

1 marks

Answer: C

This question in 0970/21 May/June 2020

40 When a river is polluted by fertiliser, the following processes may occur. 1 increased aerobic respiration of decomposers 2 increased growth of producers 3 decreased oxygen concentration in the water What is the correct sequence for these processes? A 1 → 2 → 3 B 1 → 3 → 2 C 2 → 1 → 3 D 2 → 3 → 1

1 marks

Answer: C

This question in 0970/22 May/June 2020

40 The hormones from the female contraceptive pill can pollute water courses. What effect do they have? A decrease the amount of oxygen for fish B decrease the sperm count of men C increase the growth of producers D increase the number of decomposers

1 marks

Answer: B

This question in 0970/22 Oct/Nov 2020

40 Which hormones can cause the feminisation of male fish? A adrenaline and progesterone B adrenaline and testosterone C oestrogen and progesterone D oestrogen and testosterone

1 marks

Answer: C

This question in 0970/21 May/June 2021

40 The process of eutrophication begins with the increased availability of nitrate ions and other ions in water. The processes involved in eutrophication are listed. 1 increased aerobic respiration by decomposers 2 increased death of producers due to lack of light 3 rapid growth of producers 4 oxygen concentration in the water decreases and more organisms die What is the correct sequence? A 3  2  1  4 B 3  4  2  1 C 4  1  2  3 D 4  1  3  2

1 marks

Answer: A

This question in 0970/22 May/June 2021

40 If the nitrate concentration in a lake increases, fish may die due to the events listed. 1 increased aerobic respiration by decomposers 2 increased decomposition of dead producers 3 increased growth of producers 4 reduction in dissolved oxygen Which sequence of events would lead to the death of the fish? A 1  3  2  4 B 2  1  4  3 C 3  2  1  4 D 3  4  1  2

1 marks

Answer: C

This question in 0970/22 Oct/Nov 2021

38 The bloodworm is an organism that is found in heavily polluted water. The diagram shows where raw sewage flows into a river. Where would there be fewest bloodworms? input of raw sewage A D B C direction of flow

1 marks

Answer: A

This question in 0970/21 May/June 2023

38 The diagram shows the positions of four farms and the concentrations of nitrate at different points in a river. Which farm is likely to have been using too much fertiliser on its land? farm C direction of flow farm A farm D farm B direction of flow 60 40 nitrate concentration / ppm 20 0

1 marks

Answer: A

This question in 0970/22 May/June 2023

39 What are two reasons for organisms becoming endangered? 1 habitat destruction 2 monitoring 3 education 4 pollution 5 captive breeding programmes A 1 and 4 B 1 and 5 C 2 and 3 D 3 and 4

1 marks

Answer: A

This question in 0970/21 May/June 2024

37 A farmer has a small pond on their farm land. One year, most of the organisms in the pond die. The next year, the farmer decreases their use of nitrate fertilisers and fewer organisms in the pond die. Which statement explains why this will help increase the number of organisms living in the pond? A There is a decrease in dissolved oxygen due to an increase in decomposition. B There is a decrease in dissolved oxygen due to an increase in photosynthesis. C There is an increase in dissolved oxygen due to a decrease in decomposition. D There is an increase in dissolved oxygen due to a decrease in photosynthesis.

1 marks

Answer: C

This question in 0970/22 Oct/Nov 2024

39 Which source of pollution can cause eutrophication? A carbon dioxide B methane C non-biodegradable plastic D sewage

1 marks

Answer: D

This question in 0970/21 May/June 2025

39 The graph shows the global emissions of carbon dioxide and methane from 1990 to 2015. 40 000 35 000 30 000 25 000 key emissions / million 20 000 carbon dioxide tonnes 15 000 methane 10 000 5000 0 1990 1995 2000 2005 2010 2015 year A student makes four statements about carbon dioxide and methane. ● Carbon dioxide and methane were the only sources of greenhouse gases produced in 1990. ● Carbon dioxide emissions continue to rise to the present day. ● Carbon dioxide has a greater effect on climate change than methane. ● Methane emissions were lower than carbon dioxide emissions between 1990 and 2015. How many statements are supported by these data? A 1 B 2 C 3 D 4

1 marks

Answer: A

This question in 0970/22 Oct/Nov 2025