Class Notes (838,009)
Canada (510,616)
Biology (1,303)
BIOL 103 (255)
Lecture

Population Genetics and Causes of Microevolution

3 Pages
72 Views
Unlock Document

Department
Biology
Course
BIOL 103
Professor
Peter T Boag
Semester
Winter

Description
Population Genetics and Causes of Microevolution - Changes in allele frequencies of a population caused by microevolution: o Mutation (origin, but weak for evolution) o Nonrandom mating o Genetic drift o Gene flow o Natural selection o Table 22.1 - Hardy-Weinberg principle o Provides a ‘Null Hypothesis’ for what happens to gene frequencies between generations in absence of evolution o What we expect to happen in gene frequencies o Explains stability of allele frequencies over successive generations in populations at genetic equilibrium with random mating o Essential to understanding mechanisms of evolutionary change o For equilibrium to obtain, the following conditions must be true  Populations are very large  Individuals mate at random  Immigration and emigration are zero  Mutation is rare or absent - Hardy-Weinberg Equations o p = frequency of dominant allele o q = frequency of recessive allele o p + q = 1 2 2 o Genotype frequencies in population reflect the relationship p + 2pg +q = 1 o 2pq is frequency of heterozygous genotype o q is frequency of homozygous recessive genotype - In sexual reproduction, parental genotype frequencies determine allele frequencies in gamete pool - Alleles randomly unite into zygotes forming new genotypes, whose frequencies are the product of allele frequencies in the gamete pool – if parent frequencies change, take only 1 generation to reach new equilibrium - Cause of microevolution: o Nonrandom mating  Inbreeding; selfing or matings between close relatives  Can produce inbreeding depression, if population previously outbred  Expect every generation to produce some homozygous offspring, but homozygous offspring can only produce homozygous offspring  Does not change allele frequencies, but genotype frequencies do change as heterozygotes disappear (if return to random mating)  Assortative mating common in animals, e.g. tall humans prefer tall males  Both eventually decrease frequency of heterozygous genotypes  Inbreeding depression occurs in Lobelia cardinalis when plants self- fertilize – can outcross, or produce C (C produced by self-fertilization)  Self-fertilization has reproductive individuals with fitness that is low  Inbreeding depression is detectable in humans in first-cousins and closer unions o Genetic Drift  Random changes of allele frequencies in small populations, often due to ‘sampling’ = genetic drift  Decreases genetic variation within a population; may increase differences between populations  Changes are usually not adaptive, but can lead to population differentiation, even set the stage for speciation  Purely statistical p
More Less

Related notes for BIOL 103

Log In


OR

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


OR

By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.


Submit