The Theory Evolution via natural selection How did different organisms arise? How are they related? Listen to the audio portion of this lecture by viewing in ‘presentation mode’ and clicking on the speaker icon.

Voyage of the Beagle 1831, ship sets sail for a voyage around the world 1831, ship sets sail for a voyage around the world Aboard is Charles Darwin, a 21 yr old college graduate, serving as ships’ naturalist (unpaid) Aboard is Charles Darwin, a 21 yr old college graduate, serving as ships’ naturalist (unpaid) Observations and evidence collected on this voyage changed biology forever. Observations and evidence collected on this voyage changed biology forever.

The voyage of the HMS Beagle

Darwin’s observations Fossils: he finds evidence of extinct animals Fossils: he finds evidence of extinct animals Diversity: animals and plants vary widely in similar habitats Diversity: animals and plants vary widely in similar habitats Why are some species widely found, others live only in one place? Why are some species widely found, others live only in one place? Giant sloth claw Land and marine iguanas

Ideas that shaped Darwin’s thinking Lyell: Geology shows evidence of an ancient earth with geologic processes happening over extended periods of time Lyell: Geology shows evidence of an ancient earth with geologic processes happening over extended periods of time Lamarck: traits of a parent can be passed on to the offspring Lamarck: traits of a parent can be passed on to the offspring Malthus: population size is determined by limiting factors: food, living space Malthus: population size is determined by limiting factors: food, living space

Publication of “On the Origin of the Species” In 1859 Darwin proposes a mechanism to explain the complexity of life In 1859 Darwin proposes a mechanism to explain the complexity of life Theory: evolution has been going on for billions of years, and continues today. Theory: evolution has been going on for billions of years, and continues today.

Evolutionary theory Inherited variation: all species have individuals that are slightly different from each other Inherited variation: all species have individuals that are slightly different from each other Over reproduction: species produce excess offspring Over reproduction: species produce excess offspring Struggle for existence: there is competition to survive Struggle for existence: there is competition to survive Natural selection: the weak will die off Natural selection: the weak will die off Survival of the fittest: the members best adapted to their environment will live to reproduce, and their traits will be passed on to their offspring Survival of the fittest: the members best adapted to their environment will live to reproduce, and their traits will be passed on to their offspring

Evolution is Descent with modification Each species alive today descended, with changes, from other species Each species alive today descended, with changes, from other species All species, living and extinct, were derived from common ancestors All species, living and extinct, were derived from common ancestors A single “tree of life” A single “tree of life” links us all together

Summary Write a 5 sentence paragraph (in your own words) that summarizes the key point of this lecture. Write a 5 sentence paragraph (in your own words) that summarizes the key point of this lecture.