Gene pools, selection and speciation

Gene pools, selection and speciation

1. Hardy-Weinburg

   • Equation
     • p+q = 1.0
     • p^2 +2pq + q^2 = 1.0
     • p= dominant allele frequency
     • q= recessive allele frequency
     • p^2 = homozygous dominant frequency
     • 2pq = heterozygous frequency
     • q^2 = homozygous recessive frequency
   • Principles
     • Large population
     • No immigration/emigration
     • Mating is random
     • Genotype have same reproductive success
     • No gene mutation
   • (same allele frequencies in each generation)
   • Serious recessive condition
     • No reproduction
       • Change in allele frequency in next generation

2. Some phenotype is less likely to reproduce

   • Differential Reproductive Success
   • Process of which allele frequency change (each generation) due to this is...
     • Natural Selection

3. Selection

   • Directional Selection
     • Associated with change in environment
     • Acts against one extreme
       • Favours the other extreme
   • Disruptive Selection
     • Both extremes are favoured
   • Stabilising Selection
     • Associated with a stable environment
     • Acts against both extremes

4. Speciation

   • Types
     • Allopatric Speciation
       • Same species that are geographically isolated
     • Sympatric Speciation
       • New species arises without geographical isolation
   • Steps
     • 1. Geographical Isolation
     • 2. Seperate gene pools
       • No interbreeding/gene flow between populations
     • 3. Variation due to mutation
     • 4. Different selection pressures
       • Different abiotic/biotic conditions
       • Different Environments/habitats
     • 5 Differential Reproductive Success
       • Survive and Reproduce
     • 6. Leads to change/increase in allele frequency

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