Evolution u Evolution any process of change over

Evolution

u. Evolution – any process of change over time. u. Geologic Time – A record of Earth’s history found in rocks and fossils. u. Earth’s age – about 4. 6 billion yrs. u Relative age of rocks determined by their position.

Grand Canyon u. Older fossils show that life forms started as simple, single celled organisms.

u. History of Evolution u 1. Lamarck (1809) – thought evolution resulted from striving for improvement. u - a) organs appeared as needed and could be improved with use. Then passed to offspring.

-b) If not needed, organs disappeared in next generation. u -c) Transmission of acquired traits. (lose an arm, offspring could be born that way) u u Weismann(1870) – disproved Lamarck. Cut off tails of mice and all the offspring still had tails.

Charles Darwin

The Voyage of the Beagle

u Darwin’s Theory of Natural Selection based on: u 1. Overproduction – due to limited space and food, more offspring produced than can survive. u 2. Competition - members of a population compete for food and mates.

u 3. Variation – because of different characteristics, some better able to survive. u 4. Survival of the fittest – those that survive longer will live to reproduce. u 5. Transmission of favorable traits – offspring of fittest parents will inherit their favorable traits.

u 6. Evolution – as populations change due to these new favorable traits, that is evolution ameoba sisters natural selection

Modern Theory of Evolution u Variation – caused by “shuffling” of genes during sexual reproduction. Also caused by random mutations u Natural Selection – due to passing on of genes for favorable traits. u Geographic Isolation – 1 species can become 2 different ones if a population gets separated by mountains or plates separating.

u Environmental Changes – stable environment = not much change u - changes in the environment select for different traits to become successful. u ex: antibiotics lead to resistant strains of bacteria

Rates of Evolutionary Change Gradualism – changes occur little by little over long time. u 2. Punctuated Equilibrium – things are stable until brief, fast change occurs. Then stable again. u 1.

u ** Species with short life spans and large numbers of offspring can change very quickly. Ex: bacteria, insects Similarities between related species 1. Comparative Anatomy – similar body structures

u Homologous Structures – same structure different function

u. Analagous structures – similar function but different structure. Not close relationship

u. Similar parts cell

u. Similar embryos