15.2 Theories of Evolution

Evolution Organisms change over time…

Lamarck –Proposed Organisms that are similar have similar ancestors –Explained Acquired traits –Arise as result of organism’s experience and are passed to offspring –Ex: giraffe’s long neck Darwin –Proposed Descent with modification –Explained Modification by natural selection

Darwin’s Modification by Natural Selection 1. New forms in fossil record are descendants of older species with changes –Recent and remote common ancestors –Remember phylogenetic trees –Descent with modification 2. Individuals with favorable traits or adaptations to a particular environment are more likely to survive and reproduce and therefore pass their traits on to their offspring: Natural Selection The characteristics of the population change over time

Details of Darwin’s Life Born 1809 Son of physician Sailed on HMS Beagle for 5 years as the ship’s naturalist 1831 Influenced by “Principles of Geology” by Charles Lyell –Uniformitarianism- forces change Earth’s surface continuously –Darwin concluded the Earth is very old

Darwin continued Upon return after voyage, he analyzed data of interest Influenced by Thomas Malthus essay on populations –Competition within population Published “on the origin of species by means of natural selection” in 1859 Wallace reached same conclusions

Fitness Today: an organism’s FITNESS is its genetic contribution to its population High Fitness –Well adapted –Adaptive advantage –Successful reproductive rate