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An environmental scientist investigated the pollution of a stream by recording the number of bloodworms at various locations in the stream - Edexcel - GCSE Biology - Question 3 - 2017 - Paper 1
Question 3
An environmental scientist investigated the pollution of a stream by recording the number of bloodworms at various locations in the stream. (a) State the term used ... show full transcript
Worked Solution & Example Answer:An environmental scientist investigated the pollution of a stream by recording the number of bloodworms at various locations in the stream - Edexcel - GCSE Biology - Question 3 - 2017 - Paper 1
Step 1
State the term used to describe organisms that show pollution levels in air or water.
Answer
The term used to describe organisms that indicate pollution levels in air or water is 'indicator species'. These are living organisms that can provide information about the environmental conditions, especially concerning pollution.
Step 2
Calculate the mean number of bloodworms at a distance of 75 m along the stream.
Answer
To calculate the mean number of bloodworms found at a distance of 75 m, we add the values from all three repeats and divide by the number of repeats.
The values are:
- Repeat 1: 15
- Repeat 2: 15
- Repeat 3: 18
Mean calculation: ext{Mean} = rac{(15 + 15 + 18)}{3} = rac{48}{3} = 16
Thus, the mean number of bloodworms at a distance of 75 m is 16.
Step 3
Describe what these results show about the pollution level of the stream.
Answer
The results indicate variations in the number of bloodworms at different distances along the stream. Notably, lower counts of bloodworms (1-2) at 5 m and 25 m suggest high pollution levels at these points, as indicator species typically decline in polluted environments. In contrast, a higher count (12-20) at 55 m implies better water quality. The mean count at 75 m being 16 further supports a healthier ecosystem. Finally, the increase to 26 at 95 m indicates a significant recovery in biodiversity, likely due to reduced pollution further downstream.