In the times before modern medicine, giving birth used to be a very dangerous time for women. There were often complications with the delivery that meant that babies were less likely to survive than they are today.
Babies that were very small when they were born were more likely die during their infancy. Babies that were very large when they were born were more likely to be too difficult for the mothers to deliver on their own and could lead to fatal complications during their delivery.
State the type of selection that occurred during this time.
A scientific study was carried out in 2017 on a small community of people in Berne, Indiana called the Amish. This community mixes very infrequently with the wider US population and tend to have children with people in their own community.
The study found that a large number of individuals in their community possessed a mutated allele that increased their life expectancy by ten years on average.
Explain why this allele is found in much higher percentages in this community compared to the rest of the US population.
One mark is available for clarity of communication throughout this question.
a)
The image below shows a normal distribution curve.
Sketch three graphs to show how this normal distribution curve would change if the population is exposed to directional selection, stabilising selection, and disruptive selection.
