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In the 19th century the destruction of wetland habitats caused the extinction of the bittern in the UK - Edexcel - GCSE Biology Combined Science - Question 4 - 2023 - Paper 1
Question 4
In the 19th century the destruction of wetland habitats caused the extinction of the bittern in the UK. Figure 5 shows a bittern. Restoration of the habitats has le... show full transcript
Worked Solution & Example Answer:In the 19th century the destruction of wetland habitats caused the extinction of the bittern in the UK - Edexcel - GCSE Biology Combined Science - Question 4 - 2023 - Paper 1
Step 1
(i) Calculate the percentage increase in the number of males from 1997 to 2021.
Answer
To calculate the percentage increase use the formula:
ext{Percentage Increase} = rac{ ext{New Value} - ext{Old Value}}{ ext{Old Value}} imes 100In this case, the Old Value is 11 and the New Value is 221:
ext{Percentage Increase} = rac{221 - 11}{11} imes 100 = rac{210}{11} imes 100 \\ ext{Percentage Increase} \\ ext{≈ 1909.09 \%}Step 2
Step 3
(iii) Explain, using your knowledge of natural selection, why being closely related could make the bitterns susceptible to extinction.
Answer
Closely related bitterns may have similar genetic traits, which can reduce genetic diversity. This lack of diversity can lead to increased vulnerability to diseases and environmental changes. If a disease affects one individual, it may likely affect many others, leading to potential extinction of the population.
Step 4
Describe how selective breeding can be used to produce a large population of animals that are not closely related.
Answer
Selective breeding can be utilized by choosing individuals from different genetic backgrounds to mate, ensuring that the offspring have a diverse genetic makeup. This method minimizes the risk of inherited genetic disorders and maintains healthy population dynamics.
Step 5
Complete the Punnett square to show how sex is determined in birds.
Answer
Fill in the Punnett square as follows:
| | Z | W |
|------|--------|--------|
| Z | ZZ | ZW |
| Z | ZZ | ZW |
This shows that there is a 50% chance of producing male (ZZ) and a 50% chance of producing female (ZW) offspring.