Evolution NOtes

1. Evolution NOtes Pre-AP biology – Part 1

2. Evolution • Definition = process that results in heritable changes in a population spread over many generations • **GENETIC CHANGE • OVER TIME

3. History of Evolution • 1st described by Jean Baptiste Lamarck • Similar species descended from a common ancestor • The more a species used a structure the more likely it would be passed on • Ideas supported by fossil record and similar looking species

4. History of Evolution • Later studied by Charles Darwin • Species are modified by natural selection • Proportion of organisms with favorable traits increases in a population

5. Natural Selection • Organisms best suited to their environment reproduce more successfully than other organisms

6. Darwin’s Theories • Descent with modification • newer forms appearing in fossil record are modified descendants of ancient species • All species descended from one or a few original species

7. Support for Descent with Modification • Similar organisms have arisen in the same geographical location • Ex. Marsupials are only in Australia

8. Natural Selection • Organisms with the most favorable traits are more likely to survive and have offspring that pass on those sametraits

9. Adaptation • Genetic changeswhich allow an organism to become more suited to an environment.

10. Fitness • An organisms ability to survive and reproduce successfully

11. Rapid change • If an environment changes too rapidly, genetic adaptation can’t occur and a species can become extinct.

12. Stabilizing Selection • Individuals with the average form of the trait have the highest fitness • For example: lizard size • Large lizards are easy to spot and eaten by predators • Small lizards are not fast enough to escape predators • Medium-sized lizards are most likely to survive

13. Directional Selection • Individuals that display a more extreme form of a trait have a greater fitness than individuals with an average form of a trait • For example: anteaters • Anteaters reach into termite nests with their tongues • Termites adapt to build deeper nests • Anteaters with longer tongues have higher fitness

14. Disruptive Selection • Individuals with either extreme variation of a trait have a greater fitness • Ex. Limpets • White limpets are hard to see on rocks with goose barnacles • Dark limpets are hard to see on bare rocks • Birds can easily see medium colored limpets which show up in either case

15. Sexual selection • Elaborate displays to attract a mate, organisms want to attract the most mates http://www.cornell.edu/video/?VideoID=2398

16. Artificial Selection • Humans breed organisms specifically for the traits we think are most desirable.

17. Evidence for Evolution Pre-AP Biology - Part 2

18. Homologous Structures • = same body parts, modified in different ways during evolution

19. Vestigial Structures • = structure that had a purpose in an ancestor but no longer serves a useful function to the modern organism • Ex. Human tail bone and appendix • Pelvic bones in snakes • Pelvic bones & 4 chambered stomachs in whales

20. Embryology • Early stages of vertebrate embryos are very similar

21. Macromolecules • Proteins, RNA, DNA • # of differences in amino acid sequence in homologous proteins of 2 species is proportional to the amount of time passed since two species shared a common ancestor.

22. Fossil Record • - Information about organisms that used to exist on earth • - Tiny changes apparent through time

23. Patterns of Evolution Pre-ap Biology – Part 3

24. Coevolution • Change in two species as a result of close association with each other • Predators/ Prey • Pollinators and the plants they pollinate

25. Convergent • Two unrelated organisms develop similar characteristics due to a similar environment • Ex. A bat and a bird

26. Divergent • Two related species develop different characteristics due to different environments • Ex. Giraffe and a Cow