Chapter 20-22 Flashcards
Genetic variation
different alleles of genes found within individuals of a population
Evolution
how an entity changes through time, caused by natural selection. Requires genetic variation
Evolution by natural selection occurs when:
1. phenotypic variation exists among individuals within population
2. Variation among individuals result in difference in number of offspring surviving in next generation
3. Phenotypic variation has genetic variation
Hardy-Weinberg Equilibirum
Original proportions of genotypes in a population will remain constant as long as following assumptions are met:
1. No mutation takes place
2. No genes are transferred to or from other sources (no immigration or emigration takes place)
3. Mating is random
4. Population size is very large
5. No selection favoring one genotype over another occurs
Gene flow
Movement of alleles from one population to another
Genetic drift
frequencies of particular alleles drastically change by chance. Occurs randomly
Sexual selection
Competition for mates
Intrasexual: competitive interactions between members of one sex
Intersexual selection: mate choice
Disruptive selection
selection acts to eliminate intermediate types
Directional selection
eliminates one extreme from array of phenotypes
Stabilizing selection
eliminates both extremes from array of phenotypes, increase frequency of common intermediate type
Bottleneck effect
Happens when size of population is severely reduced, events like natural disasters that decimate population and leave behind small, random assortment of survivors. Population becomes more susceptible to effect of genetic drift from generations
Founder effect
Occurs when small group of individuals breaks off from larger population to establish colony. New colony isolated from original population, founding individuals don’t represent full genetic diversity of original population
Gene pool
consist of all copies of all genes in population
