We the Galapagos Islands

Chapter 15 Part 2: Evolution Introduction Continued…

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Natural Selection• Darwin’s greatest contribution was his

concept of natural selection

• In the struggle for survival, the most fit- the fastest prey, the strongest predator, the one with the sharpest claws, wins the game of survival. Survival of the fittest.

• Natural Selection – process by which individuals that are better suited to their environment survive and reproduce most successfully

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Evolution by Natural Selection• Fitness = the ability to survive and

reproduce in a specific environment

• Adaptation = any inherited characteristic that increases an organisms chance of survival

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Proof for Evolution• Fossil record = Darwin argued

that the fossil record provided evidence that living things have been evolving for millions of years

• Geographic Distribution of living species: Descent with modification, says that similar species in similar environments but in different locations, were products of different evolution paths

Beaver

Muskrat

Beaver andMuskrat

Coypu

Capybara

Coypu andCapybara

They all look like rats to me.

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Homologous Body Structures

• Homologous structures all develop from the same embryo tissues but have different functions in the adult organism.

Turtle Alligator Bird Mammal

Ancient lobe-finned fish

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Vestigial organs• Why do we need our appendix?• It’s useless now, but it may have served

some function in our past• Vestigial organs = organ with little or no

function, left over from the past, ex. appendix

If you can live without it, with no medical

help, then it’s useless!