They supposed that such mutant forms constituted new species and thus believed that natural selection was not necessary to account for the origin of species. The last influential mutationist was Richard Goldschmidt

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#XL - T Zoology

Ockham’s principle - Principle of parsimony

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The Forces of Evolution

Mutation, 

Genetic drift

Gene flow or migration

Selection

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Nonrandom Mating Nonrandom mating affects the way in which alleles combine to form genotypes and alters the genotypic frequencies of a population.

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Positive assortative mating

Individuals' mate with others who are like themselves phenotypically for selected traits. The net effect of positive assortative mating is a progressive increase in the number of  homozygous genotypes (AA and aa)

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#XL - T Zoology