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4 (a) 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
4 (a) 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 habita... show full transcript
Worked Solution & Example Answer:4 (a) 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, we use the formula:
ext{Percentage Increase} = rac{ ext{New Value} - ext{Old Value}}{ ext{Old Value}} imes 100
In this case, the old value (1997) is 11 and the new value (2021) is 221.
So,
ext{Percentage Increase} = rac{221 - 11}{11} imes 100
This simplifies to:
rac{210}{11} imes 100 \\ ext{Percentage Increase} ext{ approximately } 1909.09 ext{ %}
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 reduced genetic diversity.
This lack of genetic variation means that if a disease or environmental change affects one individual, it could potentially affect all, as they share similar genetic traits.
Consequently, a disease could wipe out a large portion of the population, leading to extinction.
Step 4
(b) Describe how selective breeding can be used to produce a large population of animals that are not closely related.
Answer
Selective breeding can be used to enhance genetic diversity by choosing individuals from different genetic backgrounds to breed.
By selecting mates that are not closely related, breeders can increase the overall genetic variation in the offspring.
This mitigates the risks associated with inbreeding and helps to create a healthier population.
Step 5
(c) 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 ZZ and females are heterozygous ZW, should look like this:
Z | Z
--------------
Z | ZZ | ZZ
--------------
W | ZW | ZW
The resulting genotypes indicate that there is a 50% chance of male (ZZ) and a 50% chance of female (ZW) offspring.