How is Evolution Measured?Hardy-Weinberg
The Hardy-Weinberg model is used to predict genotype frequencies in a population, and also determine the effects on future generations. p² + 2pq + q² = 1 In the above equation, p represents the frequency of the dominant allele in the population. Q is the frequency of the recessive. P² represents homozygous dominant individuals, q² represents homozygous recessive individuals, and 2pq represents heterozygous individuals. The development of this equation allowed scientists to make predictions for entire populations, similar to the way Punnett squares were used to make predictions about the offspring of two individuals. What Conditions Keep Populations from Evolving?Large Population Size
A large population size can prevent variation from occurring within the population. Random mutations would have a greater effect on a smaller population, because mutation in one individual would be a larger percentage of the population if the population size was smaller. Random Mating Random mating must occur to keep a population in equilibrium. If mates are selected based on specific phenotypes, then certain traits will be favored and selected for/against. No Immigration/Emigration Immigration of individuals can change the allele frequencies of the population by bringing in new genes. The same can be said for individuals leaving the population. No Net Mutation Rate Mutations will alter the composition of the population's gene pool, so these must not occur for equilibrium to be maintained. A Constant Environment When environmental conditions change, new traits may be selected for/against, resulting in natural selection that will alter the allele frequencies of the population. |
Information was gathered from these sources:
Biology: The Unity and Diversity of Life, 12th Edition
http://anthro.palomar.edu/synthetic/synth_2.htm
http://www.course-notes.org/Biology/Outlines/Chapter_23_The_Evolution_of_Populations