121766
Descrição
Mapa Mental por harry_bygraves, atualizado more than 1 year ago
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Criado por harry_bygraves
mais de 11 anos atrás
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Natural selection
- As enviromental conditions change, certain characteristics within
a randomly varying population are favoured, and natural selection
occurs. This has become known as the 'survival of the fittest'
- Fitness is defined as the ability of an organism to pass on its alleles to
subsequent generations compared with pother individuals of the same species
- Natural selection affects a gene pool by
increasing the frequency of alleles that give an
advantage, and reducing the frequency of alleles
that give a disadvantage
- Two types of natural selection; there are two different
types of selection; stabalising and directional selection.
These reflect the two different ways in which natural
selection acts on the phenotypes in a population.
- Stabalising selection - usually takes place in an
unchanging enviroment. Extremes of the phenotype range
are selected against, leading to a reduction in variation
- Dircetional selection - favours on extreme of the phenotype range
and results ina shift of the mean either to the right or to the left. This
type of selection usually follows some kind of enviromental change
- Stabalising selection - usually takes place in an
unchanging enviroment. Extremes of the phenotype range
are selected against, leading to a reduction in variation
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