What evidence do we have for evolution? (5)

Is this population evolving? What do you think? Is this population evolving?

This population IS evolving Allele frequency changes from one generation to the next

Mechanisms of Evolution

Evolution is the change in allele frequency Remember…evolution occurs Over time In populations…NOT individuals On phenotypes

Two Main Sources of Genetic Variation 1) Mutations 2) Gene Shuffling

1) Mutations Caused by mistakes during replication Any change in a sequence of DNA. Caused by mistakes during replication

2) Gene Shuffling Recombination of genes: Occurs during the production of gametes in meiosis

How Does Variety Arise? Video 2) Gene Shuffling Recombination as homologous chromosomes move independently during meiosis Crossing over: the exchange of genetic material during prophase I How Does Variety Arise? Video

Gene Pool & Allelic Frequency Gene Pool: Entire collection of all the alleles in a population Allelic Frequency: The number of times an allele appears in the gene pool

Gene Pool & Allelic Frequency Gene Pool: 12 green alleles and 8 brown alleles Allelic Frequency of green: 12/20 Allelic Frequency of brown: 8/20

Evolution is the change in allele frequency Occurs in one of three ways: Gene Flow Genetic Drift Natural Selection

1) Gene Flow ~ The movement of alleles into or out of a population Can increase or decrease genetic variation

2. Genetic Drift Random change in allelic frequencies due to chance. Decreases genetic variation

Types of Genetic Drift Founder Effect ~ A small group of individuals colonize a new habitat or new area

Types of Genetic Drift Bottleneck ~ a sharp reduction in the size of a population due to environmental events (flooding, earthquake, etc.)

3) Natural Selection Decreases genetic variation ~ Most common source of evolutionary change Decreases genetic variation

Main Mechanisms of Evolution Video