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Understanding Evolution: The Hardy-Weinberg Principle and Population Changes

The Hardy-Weinberg Principle is vital to understanding how we can know if a population is evolving or remaining stable. It states that genetic equilibrium occurs when allele frequencies remain constant across generations, indicating no evolution. Key conditions for this equilibrium include no mutations, no gene flow due to isolation, a large population size, random mating, and equal survival and reproduction. However, these conditions are rarely met in nature, leading to changes in allele frequencies and, consequently, evolution. This principle also aids in calculating allele and genotype frequencies using the Hardy-Weinberg equations.

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Understanding Evolution: The Hardy-Weinberg Principle and Population Changes

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  1. How do we know if a population is evolving?

  2. When is a population not evolving? • How do we know if a gene pool has changed? • The Hardy-Weinberg Principle can help answer these questions.

  3. The Hardy-Weinberg Principle states: • Genetic equilibrium will be reached if the frequency of alleles remains stable generation after generation. • Genetic equilibrium = no evolution occurring.

  4. Hardy-Weinberg Principle • Conditions necessary for genetic equilibrium are: • No mutation occurs • Immigration and emigration do not occur (population is isolated from other populations) - no gene flow. • Population is very large • Mating is totally random • All individuals survive and reproduce equally (no natural selection)

  5. Hardy-Weinberg Principle • It is virtually impossible to meet these conditions. • Allelic frequencies do change in populations, therefore evolution occurs. • The main application of this principle is calculating allele and genotype frequencies in a population.

  6. In a population, the sum frequency of alleles will equal 1. • This can be expressed as: • p + q = 1 • Where: • p = frequency of the dominant allele • q = frequency of recessive allele

  7. Hardy-Weinberg Equation • p2 + 2pq + q2 = 1 • Where: • p2 = frequency of individuals homozygous for the dominant allele • 2pq =frequency of heterozygous individuals • q2 = frequency of individuals homozygous for the recessive allele

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