Evolutionary theory Definitions Thoughts on evolution The evidence for evolution

1. Evolutionary theory Definitions Thoughts on evolution The evidence for evolution

2. What is evolution? the process by which characteristics of organisms change over time “Macroevolution”-studying the changes that take place over long periods of time formation of new species appearance of novel structures episodes of extinction

3. “Microevolution”- changes that occur within populations genetic variation due to natural selection adaptation- changes that increase likelihood of survival and reproduc- tion of that organism in that environment

4. Why is it called evolutionary theory? A scientific theory is an explanation of natural events based on a large number of observations and consistent with scientific principles Evidence for evolution: the fossil record comparative anatomy/embryology molecular (biochemical and DNA)

5. History of evolutionary thought I. Each organism was created at the same time and remains exactly as it was created. Also, Earth is approx.4000 years ancient Greeks (Plato, Aristotle) Judeo-Christian theology II. Age of exploration many new species discovered similarities and differences noted Discovery of fossils

6. Allosaurus (65 mya) Seed ferns (150 mya) trilobites (230 mya)

7. Smith (1700s) certain fossils are always found in the same layers; “younger” fossils are in higher layers that older ones older fossils very different from modern organisms many organisms were extinct How did different organisms appear at different times?

8. Comte de Buffon (1700s) a few founding species changed over time Cuvier (early 1800s)- catastrophism catastrophies killed off many of the founding species Hutton (1700s) and Lyell (1800s)-geologists among the first to realize that the earth is very old “Uniformitarianism”- forces of wind, water, earthquakes, volcanic eruptions etc.-lead to formation of many layers of rock, repeatedly Potassium-40 dating shows that earth is approximately 4.5 billion years old K-40 is found in volcanic rocks Half-life of K-40 is 1.25 billion years (compare to C-14, with half-life of 5730 years)

9. Biological mechanisms for evolution Lamarck- inheritance of acquired characteristics (Giraffes acquired long necks because they needed them) Darwin (and Wallace) and natural selection (Trait was already there; selection acted on it.)

10. Some types of finches observed in the Galapagos Islands

11. Gradualism or punctuated equilibrium? Eldredge and Gould, 1970s Not all species evolve at the same rate The fossil record is not complete

12. Formation of evolutionary theory

13. Evidence for evolution Fossil record: change over time

14. Anatomical record: evidence of a common ancestor

15. Homologous structures

16. “Vestigial structures”: signs of common ancestry

17. Embryology: embryos of vertebrates have many features in common (gill slits, tail)

18. Biochemical and genetic evidence All living organisms have DNA and RNA the nucleotides are biochemically identical Many essential molecules are so similar they have been compared to deduce divergence hemoglobin cytochrome c

19. macaque human lamprey bird dog frog Time # differences between human andother vertebrates (amino acids in hemoglobin)

20. “Molecular clocks,” p. 239 Why do pseudogenes evolve more rapidly than genes like histone or cytochrome C? Histone: a protein that helps stabilize the structure of DNA in a chromosome Cytochrome c: plays a role in aerobic Respiration Pseudogene: a DNA sequence that resembles a gene but does not function

21. Darwin (and others) observed artificial selection Breeding “superior” livestock and crops; Dogs (some dog species are so different from each other they can’t mate without assistance)

22. Natural selection and adaptive evolution Darwin: adaptation to environment closely related to species formation Example of natural selection: antibiotic-resistant bacteria

24. Darwin didn’t know about genetics. Evolutionary biology and genetics came together many years later: Population genetics Population: group of individuals of the same species living in the same area at the same time (and tending to breed with each other)

25. Sources of genetic variation Random processes mutation sexual recombination Natural selection is nonrandom

27. Gene pool All alleles in all individuals making up a population. Say you have two alleles for a trait, p and q. p+q=1 (why?) Hardy-Weinberg equilibrium applies if gene pool is unchanged: p2+2pq+q2=1 If p=0.8, what is q? (1-p) p2= homozygous dominants 2pq= heterozygotes q2= homozygous recessives

28. Hardy-Weinberg applies if: • Population is very large • Random mating • No mutation • No new genetic input • No natural selection

29. If p=0.8, what is q? 0.2 (1-p) p2= homozygous dominants = (0.8)(0.8)=0.64 2pq= heterozygotes 2(0.8)(0.2)=0.32 q2= homozygous recessives =(0.2)(0.2)=0.04 0.64+0.32+0.04=1 But the gene pool is not unchanging. What can change a gene pool?

30. I. Genetic drift- change of allele frequency in a small population Bottleneck effect Founder effect

33. Founder effect Tendency for hereditary disorders In isolated human populations

34. II. Gene flow- exchange of genes between populations III. Nonrandom mating IV. Mutation V. Natural selection (adaptation)

35. Directional stabilizing diversifying

36. Examples of natural selection Antibiotic-resistant bacteria Starvation gene hypothesis Microevolution is not the whole story Macroevolution- diversity of species formation of new species extinctions