Evolution

What causes genetic variation?

• mutations caused by environmental factors and errors during replication changes the DNA sequences, creating new alleles

• new genotypes = new phenotypes

• many decrease/increase chances of survival; natural selection determines which organisms with favorable traits are allowed to survive and reproduce

Natural Selection - a mechanism of evolution where organisms better adapted to their environment tend to survive and produce more offspring

• essentially, the environment selects the parents of the next generation whose phenotypes are beneficial, allowing them to pass on these traits

• selective pressures

  • 1. disease

  • 2. light, temp, H20, food, color of environment

  • 3. reproductive success

Evolution - change in allele frequency in a population over time.

• what can we use to monitor these changes? The Hardy-Weinberg Equilibrium Equation

H-W Equation - p² + 2pq + q² = 1

• equation key

  • p - dominant allele

  • q - recessive allele

    • p + q = 1

  • p² - frequency of homozygous dominant genotype

  • 2pq - frequency of heterozygous genotype

  • q² - frequency of homozygous recessive genotype

• tips when solving

  • always start with the recessive (q) allele first

  • when looking for just allele frequency - p and q

  • when looking for genotype frequency - p², q², 2pq

A population is in Hardy-Weinberg equilibrium when there is:

(1) a large population size

(2) an absence of migration

(3) no net mutations

(4) random mating

(5) an absence of selection in the population.