Figure 1 shows the sources of pollution and different levels of water pollution in a river. (i) Which part of the river will have the largest number of bloodworms? A. no pollution B. high pollution C. some pollution D. low pollution (ii) Give the names of the two indicator species from the box which provide evidence for clean water. blackspot fungus lichen freshwater shrimp sludgeworm stonefly (iii) Explain why sewage pollution in the river can decrease the oxygen levels in the water. (b) (i) Excess fertilisers can cause a build-up of nitrates in the rivers and lakes. State the name given to a build-up of nitrates in the lake. (ii) State why the build-up of nitrates is less likely to affect a river than a lake.

GCSE Edexcel Biology Nitrogen cycle: Figure 1 shows the sources of po

Figure 1 shows the sources of pollution and different levels of water pollution in a river - Edexcel - GCSE Biology - Question 1 - 2020 - Paper 1

Question 1

Figure 1 shows the sources of pollution and different levels of water pollution in a river. (i) Which part of the river will have the largest number of bloodworms? ... show full transcript

Worked Solution & Example Answer:Figure 1 shows the sources of pollution and different levels of water pollution in a river - Edexcel - GCSE Biology - Question 1 - 2020 - Paper 1

Step 1

Which part of the river will have the largest number of bloodworms?

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Answer

The part of the river with 'low pollution' will have the largest number of bloodworms. Typically, bloodworms thrive in environments that are less polluted and have higher oxygen levels.

Step 2

Give the names of the two indicator species from the box which provide evidence for clean water.

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Answer

The two indicator species that provide evidence for clean water are 'freshwater shrimp' and 'stonefly'. These species are sensitive to pollution and their presence indicates a healthier aquatic environment.

Step 3

Explain why sewage pollution in the river can decrease the oxygen levels in the water.

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Answer

Sewage pollution introduces organic matter into the water, which serves as food for bacteria. As bacteria break down this organic material, they consume a significant amount of oxygen in the process, leading to lower oxygen levels in the water. This process is known as biochemical oxygen demand (BOD), and reduced oxygen levels can harm aquatic life.

Step 4

State the name given to a build-up of nitrates in the lake.

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Answer

The build-up of nitrates in a lake is known as 'eutrophication'. This process can lead to excessive algal blooms, which further decreases oxygen availability in the water.

Step 5

State why the build-up of nitrates is less likely to affect a river than a lake.

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Answer

The build-up of nitrates is less likely to affect a river than a lake because rivers have flowing water. This movement helps to dilute and disperse nitrates quickly, minimizing their concentration in any one area. In contrast, lakes can trap these nitrates, leading to higher concentrations and more significant ecological impacts.

Figure 1 shows the sources of pollution and different levels of water pollution in a river - Edexcel - GCSE Biology - Question 1 - 2020 - Paper 1

Worked Solution & Example Answer:Figure 1 shows the sources of pollution and different levels of water pollution in a river - Edexcel - GCSE Biology - Question 1 - 2020 - Paper 1

Which part of the river will have the largest number of bloodworms?

Give the names of the two indicator species from the box which provide evidence for clean water.

Explain why sewage pollution in the river can decrease the oxygen levels in the water.

State the name given to a build-up of nitrates in the lake.

State why the build-up of nitrates is less likely to affect a river than a lake.

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