- Genetic drift, founder effect and bottleneck effect all tend to reduce genetic biodiversity
Genetic drift
- Is the change in the frequency of alleles in the gene pool of a small population as a result of chance. It can be the loss of alleles from the gene pool.
- In a large, random mating population, the allele frequency is similar to the previous generation
- In a small population, the allele frequency can by chance drift towards an increase in frequency of one allele and reduce frequency/lead to a loss of another allele
Founder effect
- A founder population is a small group of organisms that colonise a new isolated area such as an island. Allele frequencies may be different to the original population as some alleles would not be present or be reduced. eg New Zealand has a lot of birds species created by founder effect like the white faced heron
Bottleneck effect
- Is where the population is suddenly reduced in numbers to a small size eg environmental effect like earthquake, flood or human action.
- As the population falls rapidly, a range of alleles will decrease and frequency changes. If the population then increases, it will have reduced genetic biodiversity.