Genetic diversity and adaptation

What is genetic diversity?

The number of different alleles of genes in a population

Natural selection

• random mutation can result in new alleles of a gene

• in certain environments, the new allele might benefit its possessor, leading to increased reproductive success

• advantageous allele is inherited by members of the next gen

• result = over many generations, the new allele increases in frequency in the population

Directional selection + bacteria

Selection may favour individuals that vary in one direction from the mean of the population - this changes the characteristics of the population e.g. bacteria resistance to penicillin

• spontaneous mutation occurred in the allele of a gene in a bacterium that enabled it to make a new protein

• protein able to break down penicillin

• surviving bacterium divided by binary fission and built up a population of penicillin-resistant bacteria

Stabilising selection

Selection may favour average individuals - this preserves the characteristics of a population e.g. human birth weight

• mortality rate is greater at the two extremes

• infants with highest and lowest birth masses are more likely to die while those around the mean are less likely to die

Three types of adaptation

• anatomical - such as shorter ears and thicker fur in arctic foxes compared to foxes in warmer climates

• physiological - e.g. oxidising of fat rather than carbohydrate in kangaroo rats to produce additional water in a dry desert environment

• behavioural - e.g. autumn migration of swallows from the UK to Africa to avoid food shortages in the UK winter