Download Inbreeding and outbreeding

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 all 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 all 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.