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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 100Here, the old value is 11 (from 1997) and the new value is 221 (from 2021).
Substituting the values into the formula gives:
ext{Percentage Increase} = rac{221 - 11}{11} imes 100 = rac{210}{11} imes 100 \ \ ext{Percentage Increase} hickapprox 1909.09\ \So, the percentage increase in the number of males from 1997 to 2021 is approximately 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
Being closely related can lead to a lack of genetic diversity among the bittern population. This reduced genetic variability means they may be more susceptible to diseases and environmental changes, as all individuals might react similarly to threats. If a disease affects one, it is likely to impact all closely related individuals. Furthermore, this lack of variation can limit the population's adaptability to changing conditions, making them more vulnerable to extinction.
Step 4
Describe how selective breeding can be used to produce a large population of animals that are not closely related.
Answer
Selective breeding involves choosing individuals with desirable traits to mate, ensuring they are not closely related to maintain genetic diversity. By selecting different breeding pairs over several generations, the offspring will display a range of traits from both parents, ultimately creating a healthy population with minimized risks of genetic disorders. This practice promotes the emergence of strong and resilient traits in the offspring.
Step 5
Complete the Punnett square to show how sex is determined in birds.
Answer
The Punnett square for sex determination in birds, where males are homozygous Z (ZZ) and females are heterozygous ZW (ZW), is:
Z | Z
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Z | ZZ | ZZ
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W | ZW | ZW
This shows that the possible combinations are 50% male (ZZ) and 50% female (ZW).