Inbreeding and outbreeding Inbreeding Breeding between closely related

Inbreeding and outbreeding

Inbreeding Breeding between closely related individuals of a population (not to be confused with interbreeding which is breeding between DIFFERENT populations)

Inbreeding Breeding between closely related individuals of a population (not to be confused with interbreeding which is breeding between DIFFERENT populations) Inbreeding decreases genetic diversity

Inbreeding Breeding between closely related individuals of a population (not to be confused with interbreeding which is breeding between DIFFERENT populations) Inbreeding decreases genetic diversity Commonly used in selective breeding (or artificial selection) as it increases the chance of favourable alleles coming together resulting in desirable phenotypes.

Inbreeding Breeding between closely related individuals of a population (not to be confused with interbreeding which is breeding between DIFFERENT populations) Inbreeding decreases genetic diversity Commonly used in selective breeding (or artificial selection) as it increases the chance of favourable alleles coming together resulting in desirable phenotypes. In naturally occurring small populations (eg founder) inbreeding can affect the gene pool and genetic diversity – compounded by genetic drift.

Important effects of inbreeding Increases the proportion of homozygotes in the population similar to self-fertilisation.

Important effects of inbreeding Increases the proportion of homozygotes in the population similar to self-fertilisation. Inbreeding can result in rare recessive alleles being expressed – rare and harmful recessive alleles are normally protected by dominance. More common when parents are related.

Important effects of inbreeding Increases the proportion of homozygotes in the population similar to self-fertilisation. Inbreeding can result in rare recessive alleles being expressed – rare and harmful recessive alleles are normally protected by dominance. More common when parents are related. Selection against disadvantageous alleles results in a genetically less variable population. Repeated inbreeding forces alleles to be subject to selection = only beneficial alleles stay in the gene pool = less genetic diversity.

Important effects of inbreeding Increases the proportion of homozygotes in the population similar to self-fertilisation. Inbreeding can result in rare recessive alleles being expressed – rare and harmful recessive alleles are normally protected by dominance. More common when parents are related. Selection against disadvantageous alleles results in a genetically less variable population. Repeated inbreeding forces alleles to be subject to selection = only beneficial alleles stay in the gene pool = less genetic diversity. **Many species have adapted to reduce inbreeding**

Outbreeding Tends to increase the number of heterozygotes in a population and reduces the number the chances of harmful recessive alleles coming together.

Outbreeding Tends to increase the number of heterozygotes in a population and reduces the number the chances of harmful recessive alleles coming together. Offspring produced display hybrid vigour (increase of characteristic over parent) containing variety of alleles from their parents and tend to have greater evolutionary fitness than inbred populations.

Natural Selection The process where inheritable traits that make an individual more likely to survive long enough in its environment to reproduce become more common in the population over successive generations.

Natural Selection The process where inheritable traits that make an individual more likely to survive long enough in its environment to reproduce become more common in the population over successive generations. More organisms are produced than can survive = competition for resources

Natural Selection The process where inheritable traits that make an individual more likely to survive long enough in its environment to reproduce become more common in the population over successive generations. More organisms are produced than can survive = competition for resources Structural, physiological and behavioural features = increase fitness

Natural Selection The process where inheritable traits that make an individual more likely to survive long enough in its environment to reproduce become more common in the population over successive generations. More organisms are produced than can survive = competition for resources Structural, physiological and behavioural features = increase fitness Fitter individuals contribute more alleles to the gene pool = alleles increase in frequency. Unsuccessful phenotypes decrease – those alleles may eventually be eliminated.

Natural Selection The process where inheritable traits that make an individual more likely to survive long enough in its environment to reproduce become more common in the population over successive generations. More organisms are produced than can survive = competition for resources Structural, physiological and behavioural features = increase fitness Fitter individuals contribute more alleles to the gene pool = alleles increase in frequency. Unsuccessful phenotypes decrease – those alleles may eventually be eliminated. When there is a change in environment, other phenotypes are selected for = those alleles then increase in frequency = microevolution.