Evolution and Gene Frequencies Chapter 5 Zoology

Populations and Gene Pools Population – group of individuals of the same species occupying a given area at the same time and sharing a common set of genes Gene Pool – The sum of all alleles for all traits in a sexually reproducing population 4 ways the gene pool changes: independent Assortment, crossing over, chance fertilization, mutations

Most, if not all, Populations are Evolving Hardy-Weinberg theorem states that evolution stops only when 4 principles are met: Large population size No migration in or out No mutations Sexual reproduction must be random

Four Mechanisms of Evolutionary Change Genetic Drift - chance events influencing the frequencies of genes Gene Flow - immigration or emmigration in a population Mutation - changes in the structure of genes and chromosomes Natural Selection - certain phenotypes having an environmental advantage over other phenotypes (survival of the fittest)

Types of Selection Disruptive Selection - produces distinct subpopulations Sexual Selection - mating patterns that produce varying degrees of success of individuals of a population Stabilizing Selection - narrows the phenotypic range

Speciation Speciation – the formation of a new species (can only occur through reproductive isolation) Allopatric Speciation – occurs when populations become geographically isolated Parapatric Speciation – occur in small, local populations (ex. frogs in an isolated pond) Sympatric Speciation – occurs within a single population (brood parasites)

Rates of Evolution Phyletic Gradualism – slow, continuous change over long period of time (Darwin) Punctuated Equilibrium – rapid change, followed by periods of stasis, or no change, over long periods of time

Molecular Evolution Using molecular genetics to study base-paring in DNA is a high-tech way of tracking evolution through the genome

Mosaic Evolution