1. Evolution

2. Descent With Modification: A Darwinian View of Life Historical-context for evolutionary theory The Darwinian Revolution Evidence of Evolution

4. Historical Context-Why Resisted Resistance in Western culture-Why? Essentialism-influence of Greeks, Plato and Aristotle Role of Linnaeus-order in diversity Cuvier-founded the study of fossils, opponent to evolution Catastrophism-major changes in Earth’s crust the result of local floods, earthquakes, not gradual processes

5. Gradualism-geographic change due to slow, continuous processes Proposed by Hutton Charles Lyell, expanded gradualism to uniformitarianism geological processes are constant from the beginning to present

7. Lamark Placed fossils in context two principles: 1) use and disuse, 2) inheritance of acquired characteristics Important: 1) stated that evolution was the best explanation for fossils and extant life and 2) the earth is ancient

8. Darwin-historical background Studied medicine, prepared for the clergy HMS Beagle-chart South American coastline Darwin collected tropical specimens Role of Galapagos species Read Principles of Geology (Lyell) 1840’s had formed theory of natural selection

9. The Origin of Species Descent with modification Natural selection and adaptation: three inferences and five observations Variations exist, environment changes, selection occurs, adaptations result Malthusian influence

10. Evolutionary history Linnaeus: taxonomy Hutton: gradualism Lamarck: evolution Malthus: populations Cuvier: paleontology Lyell: uniformitarianism Darwin: evolution Mendel: inheritance Wallace: evolution

11. Evidence of Evolution Biogeography-geographical distribution of species Fossil record Comparative anatomy-significance of homologous structures and vestigal organs Comparative embryology-ontogeny recapitulates phylogeny? Molecular biology

12. Evidence of Evolution

13. Homologous structures: the existence of shared ancestry between a pair of structures, or genes, in different species Analogous structures: features of two different species that are similar in how the function, but the structure of the two features is different. Vestigial organs: genetically determined structures or attributes that have apparently lost most or all of their ancestral function in a given species

14. Darwin- “just a theory” Darwin made two claims: 1) modern species evolved from ancestral forms 2) the mechanism for evolution is natural selection Theories: conceptual frameworks with great explanatory power used to interpret facts, do not become dogma theory of evolution and fact of evolution

15. The Evolution of Populations

16. Using the Hardy-Weinberg Theorem

17. Causes of Microevolution Small scale evolution represented by a generational shift in a population’s relative allelic frequencies Genetic drift Gene flow Mutation Nonrandom mating Natural selection

18. Genetic Drift Changes in the gene pool due to chance Bottleneck effect- population drastically reduced by natural disaster Founder effect-when a few individuals colonize a new habitat

21. Gene Flow The migration of fertile individuals, or the transfer of gametes between populations

22. Mutations New mutation that is transmitted in gametes immediately changes the gene pool of a population by substituting one allele with another Very little quantitative effect on large populations in a single generation

23. Nonrandom Mating Increases the number of homozygous loci in a population Inbreeding- individuals usually mate with close neighbors rather than more distant members; reduction of the heterozygotes Assortive mating-individuals mate with partners that are like themselves in certain phenotypic characters

24. Natural Selection Variations always exist, some variants leave more offspring that others, differential success in reproduction Only adaptive form of microevolution

25. Genetic Variations-the Basis of Natural Selection Polymorphism-two or more contrasting forms (morphs) are present in noticeable frequencies Geographical variation-differing allelic frequencies in different populations Cline-a type of geographical variation that is a graded change in some trait along a geographical transect (example: body size of North American mammals increases with increasing latitude)

26. Polymorphism

28. Mutation and Sexual Recombination Mutations-produce new alleles Point mutations-single base in DNA Sexual recombination-produces new combinations with “old” alleles

29. Diploidy and Balanced Polymorphism The diploid condition “hides” most mutations Balanced polymorphism-counteracts the forces of natural selection (?) Preserves variations by heterozygous advantage and frequency-dependent selection Most variations are neutral

30. Fitness Relative contribution a an individual makes to the gene pool of the next generation Relative fitness- the contribution of a genotype compared to the contributions of alternative genotypes for the same locus Selection coefficient-relative measure of selection against an inferior genotype

31. Patterns of Selection Stabilizing selection- favors intermediate variants, selects against extremes, reduced phenotypic variations, stable environments Directional selection- favors variants at one extreme, common to new habitat colonization, changing environment Diversifying selection- opposite phenotypic extremes are favored, variable environmental conditions

32. Modes or patterns of selection

33. Sexual Selection Sexual dimorphism- distinction between secondary sexual characteristics, size, color, antlers, manes Male tends to be “showier”

34. Sexual Selection

35. The Origin of Species What is a Species? Modes of Speciation Origin of Evolutionary Novelty

36. Two Patterns of Speciation The boundary between microevolution and macroevolution Fossil record indicates that two pattern of speciation have occurred Anagenesis-unbranched lineage of organisms (phyletic evolution) Cladognesis-budding of one or more new species from a parent species that continues to exist (branching evolution)

37. Anagenesis vs. Cladogenesis

38. Macroevolution Origin of new taxonomic groups Evolutionary trends Adaptive radiation Mass extinctions

39. What Is a Species? Largest unit of a population in which gene flow is possible Reproductively isolated in natural environments Exceptions: asexual forms, extinct vs. extant forms Biological species concept first defined by Ernst Mayr 1942

40. Population, Species and Isolation Prezygotic barriers- impede mating or hinder fertilization of ova Habitat isolation Behavioral isolation Temporal isolation Mechanical isolation Gametic isolation Postzygotic barriers- hybrid zygote forms but development prevented Reduced viability Reduced fertility Hybrid breakdown

41. The biological species concept emphasizes reproductive isolation Species is a Latin word meaning “kind” or “appearance” Biologists compare morphology, physiology, biochemistry, and DNA sequences when grouping organisms

42. Reproductive Isolation Reproductive isolation is the existence of biological factors (barriers) that impede two species from producing viable, fertile offspring Hybrids are the offspring of crosses between different species Reproductive isolation can be classified by whether factors act before or after fertilization

43. Prezygotic barriers block fertilization from occurring by: – Impeding different species from attempting to mate – Preventing the successful completion of mating – Hindering fertilization if mating is successful

44. Habitat isolation: Two species encounter each other rarely, or not at all, because they occupy different habitats, even though not isolated by physical barriers Temporal isolation: Species that breed at different times of the day, different seasons, or different years cannot mix their gametes Behavioral isolation: Courtship rituals and other behaviors unique to a species are effective barriers

45. Mechanical isolation: Morphological differences can prevent successful mating Gametic isolation: Sperm of one species may not be able to fertilize eggs of another species

46. Fig. 24-4 Prezygotic barriers Habitat Isolation Individuals of different species Temporal Isolation Behavioral Isolation Mating attempt Mechanical Isolation Gametic Isolation Fertilization Reduced Hybrid ViabilityReduced Hybrid Fertility Postzygotic barriers Hybrid Breakdown Viable, fertile offspring (a) (b) (d) (c)(e) (f) (g)(h) (i) (j) (l) (k)

47. Postzygotic barriers prevent the hybrid zygote from developing into a viable, fertile adult: – Reduced hybrid viability – Reduced hybrid fertility – Hybrid breakdown

48. Reduced hybrid viability: Genes of the different parent species may interact and impair the hybrid’s development Reduced hybrid fertility: Even if hybrids are vigorous, they may be sterile Hybrid breakdown: Some first-generation hybrids are fertile, but when they mate with another species or with either parent species, offspring of the next generation are feeble or sterile

49. Speciation can take place with or without geographic separation Speciation can occur in two ways: – Allopatric speciation – Sympatric speciation

50. Types of Isolating Mechanism

51. Modes of Speciation Allopatric speciation-occurs when the initial block to gene flow is a geographical barrier that physically isolates the population Sympatric speciation-formation of a new species within the range of parent populations

52. Modes of Speciation

53. Allopatric Speciation Occurs when isolated gene pool accumulate differences by microevolution that may cause the populations to diverge in phenotype Adaptive radiation-evolution of many diversely adapted species from a common ancestor, common to islands

54. Adaptive Radiation

55. Sympatric Speciation Quick! More common in plants Frequently caused by improper cell division resulting in formation of fertile polyploids Autopolyploidy- an organism that has more than two sets of chromosomes, all derived from a single species, diploid gametes, self-pollination Allopolyploidy-polyploid hybrid created by two different species, fertile forms result of nondisjunction of gametes in one of the species

56. Sympatric Speciation

57. Punctuated Equilibrium and the Tempo of Speciation Proposed by Steven Jay Gould and Niles Eldredge in 1972 Suggests that most allopatric speciation events are the result of crises or major genetic alterations that “punctuate” long periods of stasis Rapid evolution (misleading-actually up to 100,000 years)

58. Two Models of Evolution