Natural Selection Ch. 22

Present: ~10,000,000 species extant

Recent Past: extinction Ivory-billed (1940) Carolina Parakeet (1918) Baiji River Dolphin (2002) P. Ibex (2000) Quagga (1870) Golden Toad (1989)

Past: ~5,000,000,000 species extinct

Species changes over time

Future: species continue to evolve

Evolutionary Thought Ch 22.1

Gorges Cuvier’s contribution 1796: Fossil Record Living elephant jaw vs. fossil (mammoth & mastodon) jaws The deeper the fossils, the more dissimilar to living organisms

James Hutton’s Contribution 1795: Gradualism profound geological change occurs through slow/continuous process

Charles Lyell’s Contribution 1830: Uniformitarianism geologic processes of today are the same as in the past

Big Picture Layers of the Earth show a consistently aging planet Organisms living during the past have been preserved Nearly all fossilized species are extinct Therefore: life evolves as the environment changes

Lamarck's contribution Mechanism: Use and disuse & acquired characteristics

Charles Darwin’s contribution Mechanism: Natural Selection

Alfred Wallace’s Contribution Mechanism: Natural Selection Co-published w/ Darwin

Darwin Explains natural Selection Ch 22.2

Darwin’s Life 1809-1831 Lived in England & fascinated with nature Went to school to became a physician Dropped out (disgusted by surgery) Became a clergyman 1831-1836 Invited on the HMS Beagle Hydrographic survey of South America

Darwin Observes Documented Collected Kept a Journal: The Voyage of the Beagle Collected Thousands of plants, animals, & fossils

On the Origin of Species 1836-1859 Thinks about the voyage, animal/plant collection, fossils, geology… Begins to describe the most revolutionary idea in biology Receives a letter from colleague Alfred Wallace with same idea They publish their idea together Then Darwin finishes his book

We change organisms Artificial Selection: humans modify species over many generations by selecting and breeding individuals with desired traits https://www.youtube.com/watch?v=aDmzzREXI_g http://www.hhmi.org/biointeractive/dog-breeding

We change organisms

Observations from the voyage Galapagos islands, while close to each other, contained: Various ecosystems Organisms similar to, but different from each other Each had adaptations to fit the environment

Observations For any species, population sizes would increase exponentially if all individuals born reproduce successfully Populations tend to be stable in size, except for seasonal fluctuations Resources are limited

Inference #1 Production of more individuals than the environment can support leads to a struggle for existence among individuals of a population, with only a fraction of their offspring surviving

Observations Members of a population vary extensively in their characteristics Much of this variation is heritable

Inference #2 Survival depends in part on inherited traits; individuals whose inherited traits give them a high probability of surviving and reproducing are likely to leave more offspring than other individuals

Inference #3 This unequal ability of individuals to survive and reproduce will lead to a gradual change in a population, with favorable characteristics accumulating over generations

Summary of Evolution by Natural Selection Organisms better suited to the environment are more likely to survive & reproduce than organisms less suited to the environment Mutation  Variation  Selection Individuals do NOT change; populations change

Evolution by natural selection There is a grandeur in this view of life…

Carl sagan Explains evolution http://www.youtube.com/watch?v=gZpsVSVRsZk