The Theory of Evolution

History Linnaeus – Taxonomy (similarities among species) Leclerc aka Count Buffon – Biogeography Erasmus Darwin – common descent (common ancestor, evidence vestigial organs) Cuvier – Catastrophism Hutton – Gradualism (geology) Lyell – Uniformitarianism (geology) Linnaeus -Created classification system based on similarities Leclerc - noticed that the environment affected the traits of species (they were adapted to different conditions) Erasmus - thought that organisms had common ancestors he noticed that they had vestigial organs Cuvier - noticed different layers in the Earth had different organisms and surmised that natural disasters shaped the landforms and caused species to become extinct. He believed that the appearance of “new” species (fossils) was he result of other species migrating in after the catastrophe. Hutton - proposed that the changes of landforms (laying down of soil and formation of canyons) was a slow gradual process Lyell- expanded on gradualism proposing that the changes are not just gradual but happen at a constant rate.

Lamark – Inheritance of Acquired Characteristics Malthus – food, water & shelter limit human population growth (economist) Darwin and Voyage on the Beagle 1831-1836 Wallace - 1855 essay on Natural Selection On the Origin of Species 1859 Lamark - environment caused greater use or less use resulting in changes that are passed on. Malthus - economist noticed that decrease in resources limited the growth of human populations Darwin - was hired as a naturalist on The Beagle to record new species. Noticed differences in species especially on the Galapagos islands. Noticed differences between species on the S. Amer. Mainland and the islands; also differences between species on different islands. Tortoises large dome shell/short neck on islands with more rainfall and more grass. Tortoises with flat shells that flare up In front/long necks are on dry islands and feed on tree like cacti. Finches had different beaks for different types of food depending on what was available on each island. Wallace - shared essay with Darwin on natural selection. Darwin never published his ideas that he had written since 1844. Darwin told Wallace to publish it. Wallace’s ideas forced Darwin to publish his book (lyell and friends pushed him)

Evolution Evolution is a change over time. Evolution of a species is a change in the characteristics of a species over time. Time is measured in generations. (Thus those species with shorter generations evolve more quickly.)

Ways of thinking about Evolution: It is not linear all species alive today are on the top of the evolutionary tree Wrong Correct

If humans evolved from monkeys, why are there still monkeys? This picture is flawed, but commonly used to illustrate human evolution.

Variation Variation within a species’ gene pool increases the chances of the species survival.

Selection Selection is the driving force of evolution Selection = determining which traits (genes) are going to be passed on to the next generations. There are several types of selection and various factors that affect the selection process

Types of Selection Natural Selection- those traits that give an individual an advantage over others will be passed on. (traits that give an individual a disadvantage will not be passed on) Sexual Selection = when traits that don’t give an individual a selected advantage over others, but merely aid in attracting a mate, are passed on.

Artificial selection – when humans determine which traits are passed on by choosing which individuals in a species will mate. (Think of an example.)