Evolution

Evolution – any process of change over time. Geologic Time – A record of Earth’s history found in rocks and fossils. Earth’s age – about 4.6 billion yrs. Relative age of rocks determined by their position.

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

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

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

Charles Darwin

The Voyage of the Beagle

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

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

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

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

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

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

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

Homologous Structures – same structure different function

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

Similar cell parts

Similar embryos