Theory of Evolution

Evolution Evolution is the change in allele frequencies in a population over time. Most fundamental concept in Biology. You cannot understand all the parts of Biology without understanding evolution.

Remember alleles? Example: AA, Aa, aa Alleles are the different variations of a particular genetic trait. Allelic frequency deals with how often a particular allele appears in a population. Example: AA, Aa, aa

Allele Frequency Practice Bob has 5 flowers. If each flower has 2 alleles, how many total alleles for the population? If each flower is heterozygous (Aa), how many of the alleles are dominant?

Charles Darwin the theory evolution proposed by Darwin explains how evolution works. He realized that there is a struggle for existence among individuals.

Jean Baptiste Lamarck French Naturalist 1809- published ideas on evolution

Lamarck’s Hypothesis During organism’s lifetime, physical features increase or decrease in size based on use disuse Organisms pass down acquired traits to offspring

Believed that those parts of the body used extensively would become bigger and stronger and would be passed to offspring.

Those body parts that were not used would disappear Legless salamanders

Thomas Malthus - 1798 Pop. growth limited by disease, famine, war Human population increasing faster than supply of resources

Charles Lyell Leading geologist of Darwin’s time. Believed the Earth was very old and had changed slowly over long periods of time.

Darwin’s Discoveries Darwin collected 13 types of finches that, although quite similar seemed to be different species. Some were unique to individual islands while others were on two or more islands that were close together.

Natural Selection variations within same species enable some to survive and reproduce, while those with other variations did NOT survive and reproduce. pass these variations to offspring. “Survival of fittest” Fitness – ability of an organism to survive & reproduce in its specific environment

FIT OR NAH

Main points of Darwin’s theory of natural selection: Genetic variations in populations Overproduction of offspring– struggle for existence Organisms best adapted will survive, reproduce and pass traits to next generation.

Darwin’s 5 points Write in summary section Population has variations. Some variations are favorable. More offspring are produced than survive Those that survive have favorable traits. A population will change over time.

NS against? ________ for? __________ Variations (2)?_____ Struggle to survive? ___ Trait that helped? ____ Pop. Over time? ____