genetic diversity and adaptation- chapter 9

Question 1

what is selection

Answer 1

Process by which organisms that are better adapted to their environment tend to survive and breed, while those that are less well adapted tend not to

Question 2

what is directional selection (in depth)

Answer 2

• Selection may favour individuals that vary in one direction from the mean of the population
• changes the characteristics of the population

-If the environmental conditions change, the phenotypes that are best suited to the new conditions are most likely to survive.
- Some individuals which fall to either the left or right of the meal will possess a phenotype more suited to the new conditions, these will survive and breed. They will therefore contribute more offspring to the next generation than other individuals. Over time the mean will move in that directions.

Question 3

what is stabilising selection (in depth)

Answer 3

• Selection may favour average individuals
• preserves the characteristics of a population
• If environment conditions remain stable, it is the individuals with phenotypes closest to the mean that are favoured. These individuals are more likely to pass their alleles on to the next generation.
• Those individuals with phenotypes at the extremes are less likely to pass on their alleles. Stabilising selection therefore tends to eliminate the phenotypes at the extremes.

Question 4

what adaptations could there be from there being natural selection

Answer 4

• Anatomical- such as shorter ears and thicker fur in arctic foxes.
• Physiological- oxidising of fat rather than carbohydrate in kangaroo rats to produce additional water in a dry desert - environment.
• Behavioural- such as autumn migration of swallows from the UK to Africa to avoid food shortages in the UK winter.