Introduction to Darwinian Evolution

1. Introduction to Darwinian Evolution

2. Terminology • Evolution • Accumulation of inherited changes within populations over time • Population • Group of individuals of one species that live in the same geographic area at the same time • Species • Group of organisms with similar structure, function, and behavior capable of interbreeding

3. Pre-Darwinian ideas • Aristotle (384–322 B.C.E.) • Saw evidence of natural affinities • Leonardo da Vinci (1452–1519) • Correctly interpreted fossil rocks • Jean Baptiste de Lamarck (1744–1829) • First to propose that organisms undergo change as a result of natural phenomenon • Lamarck ideas discredited when Mendel’s theories rediscovered around 1900

4. Darwinand evolution

5. Voyage of the H.M.S. Beagle • 1831 • Basis for Darwin’s theory of evolution • Darwin observed similarities between animals and plants • Arid Galapagos Islands • Humid South American mainland

6. Voyage of the H.M.S. Beagle

7. Influences on Darwin • Principles of Geology by Lyell • Artificial selection • Breeders developing many varieties of domesticated animals in a few generations • Plant varieties, such as kale and broccoli, developed from wild cabbage • Ideas of Thomas Malthus • Population growth not always desirable • Population increases geometrically; food supply increases arithmetically

8. Artificial selection in chickens: “Big Bird”

9. Artificial selection in Brassicaoleracea

10. Evolution occurs by natural selection • Adaptation • Inherited variations favorable to survival persevere • Unfavorable variations are eliminated

11. Genetic variation in emerald tree boas

12. Theory of evolution by natural selection • Proposed by both Darwin and Wallace • Based on four observations • Genetic variation exists among individuals • Reproductive ability of species causes its populations to geometrically increase • Organisms compete for resources • Offspring with most favorable characteristics is most likely to survive

13. Synthetic theory of evolution • Began in 1930s and 1940s • Combines principles of Mendelian inheritance and natural selection • Mutation provides genetic variability on which natural selection acts • Incorporates expanding knowledge in genetic, systematics, and other scientific fields

14. Wing size in female fruit flies

15. Evidence for evolution from fossil records • Direct evidence of evolution comes from fossils • Evidence shows progression from earliest unicellular organisms to organisms of today • Shows life has evolved through time

16. Exposed layers ofsedimentaryrock

17. Fossils developin differentways

18. Fossilintermediatesin whale evolution

19. Determiningthe ageof fossils:radioisotopedecay

20. Evidence for evolution from comparative anatomy • Homologous features • Derive from same structure in common ancestor • Homoplastic features • Similar functions in distantly related organisms demonstrates convergent evolution • Vestigial structures • Remnants of structures indicating adaptation

21. Homology in animals

22. Homology in plants

23. Homoplasy

24. Convergent evolution: mammals who eat ants and termites

25. Vestigial structures

26. Biogeography • Study of past and present geographic distribution of organisms • Continental drift has played a major role in evolution

27. Continental drift

28. Evidence for evolution from developmental biology • Proteins and DNA contain record of evolutionary change • Phylogeny • Evolutionary history of group of related species • Phylogenetic trees • Diagrams showing lines of descent based on molecular data

29. Phylogenetictree ofwhales andtheir closestliving relatives

30. Evolutionary hypotheses tested experimentally • Reznick and Endler • Differences in predation correlated with differences in guppies • Male coloration and behavior • Life history traits

31. Experimentalevidenceofnaturalselectionin guppies