1. Origin of Species Chapter 24

2. Darwin Natural selection One species evolves due to adaptation Adaptation does not explain why one species becomes another

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5. Speciation One species gives rise to many descendant species

6. Fig. 25-25 Recent (11,500 ya) Neohipparion Pliocene (5.3 mya) Pleistocene (1.8 mya) Hipparion Nannippus Equus Pliohippus Hippidion and other genera Callippus Merychippus Archaeohippus Megahippus Hypohippus Parahippus Anchitherium Sinohippus Miocene (23 mya) Oligocene (33.9 mya) Eocene (55.8 mya) Miohippus Paleotherium Propalaeotherium Pachynolophus Hyracotherium Orohippus Mesohippus Epihippus Browsers Grazers Key

7. Species Latin meaning “kind” or “appearance.” Morphological differences have been used to distinguish species. Differences in body function, biochemistry, behavior, and genetic makeup

9. Biological species concept Defines species as “groups of actually or potentially interbreeding natural populations which are reproductively isolated from other such groups” Species composed of populations that can mate & produce offspring

10. Species Humans have considerable diversity Belong to the same species because of capacity to interbreed.

11. Species Species are based on inter-fertility, Not physical similarity. Eastern & western meadowlarks Similar shapes & coloration Different song Prevents breeding between species.

12. Reproductively isolated Members of a population Cannot mate or produce fertile offspring Members of different species What causes reproductive isolation? What helps species to retain their identities?

13. Reproductive isolating mechanisms Prevent genetic exchange 1. Prezygotic: “before zygote” preventing formation of zygotes 2. Postzygotic: “after zygote” preventing proper development of zygotes once formed

14. Prezygotic isolating mechanisms 1. Ecological isolation 2. Behavioral isolation 3. Temporal isolation 4. Mechanical isolation 5. Gamete isolation

15. Ecological isolation Species utilize different parts of the environment May not encounter each other Examples: Lions & tigers in India Lions: open fields, in prides Tigers: forests, hunt in isolation

16. Ecological isolation Toad These species can interbreed Use different parts of the woods to breed

17. Behavioral isolation Differ in courtships Mating dances differ Mallard & Pintail ducks

18. Behavioral isolation Blue-footed boobies Courtship dance

21. Behavioral isolation Pheromones: Chemical signals used when mating Songs vary among species Lacewings: Move abdomen to create mating song

22. Temporal isolation Mating or breeding times are different Flowering times are different Wild lettuce Frogs: genus Rana 5 species live close together differ in mating seasons

23. Temporal isolation Western spotted skunk Late summer Eastern spotted skunk Late winter

24. Mechanical isolation Structural differences prevent mating Plant structures & pollen Insects

25. Gamete isolation Sperm from one species unable to fertilize egg of another Plants different shaped pollen tubes Difficult to form a hybrid

26. Postzygotic isolation 1. Hybrid mating may occur Genetic pairings can not function in embryo stage 2. Offspring are inferior Will die in nature 3. Sterile offspring

27. Postzygotic isolation Examples: Leopard frogs problems with developing eggs Mule formed from female horse & male donkey Mule is sterile

28. Fig. 24-4o (k) Mule (sterile hybrid)

29. How does reproductive isolation arise? 1. By chance A population moves to a new habitat Adapt Mate within the new population 2. Natural selection Select individuals that are able to reproduce with greater success

30. Speciation 1. Identical populations must diverge 2. Reproductive isolation must evolve to maintain these differences

31. Mechanisms of sepciation 1. Allopatric speciation (other) 2. Sympatric speciation (together)

32. Fig. 24-5 (a) Allopatric speciation (b) Sympatric speciation

33. Allopatric speciation Populations separated by geographical location More likely to develop into new species Unable to reproduce with parent population

34. Allopatric speciation Geographic barriers Island Mountain Lake Size & mobility of the animal

35. Antelope squirrels

36. Allopatric speciation Ernst Mayr First demonstrated that geographic isolation leads to speciation New Guinea Papuan kingfisher Isolated species are more distinctive

37. Allopatric speciation Hawaiian Islands

38. Adaptive radiation Organisms form new species Fill niches No competition

39. Sympatric species Distinct species live in a single location Use different parts of the habitat Behave separately (mating calls or chemicals)

40. Sympatric speciation 1. Instantaneous speciation 2. Disruptive selection

41. Instantaneous speciation Polyploidy: Individual has more than two copies of chromosomes Autopolyploidy: All chromosomes from one species Allopolyploidy: Two species hybridize

42. Instantaneous Tetraploids (4 sets of chromosomes) Self pollinate or mate with another tetraploid Over time become fertile Established a new species

43. Polyploidy

44. Hugo de Vries---primrose

45. Polyploidy More common in plants Plants such as wheat, cotton, sugarcane Some animals such as insects, fish & salamanders

46. Disruptive selection Two distinct phenotypes evolve into separate species Lake Victoria Cichlid fishes

48. Hybrid zones Region where different species mate Characteristics are a combination of features of both populations Hybrid is formed

49. Fig. 24-13b Fire-bellied toad, Bombina bombina

50. Fig. 24-13a Yellow-bellied toad, Bombina variegata

51. Hybrid zones 1. Increases reproductive barriers Maintains 2 species 2. Two species fuse 3. Occasional hybrid is still formed Sexual preference Environment

52. Pace of evolution 1. Gradualism 2. Punctuated equilibrium

53. Pace of evolution Gradualism Changes occur slowly over time Accumulation of small changes over time

54. Gradualism

55. Pace of evolution Fossil record Many species appear as new forms rather suddenly (in geologic terms) Persist essentially unchanged Then disappear from the fossil record.

56. Punctuated equilibrium

57. Pace of evolution Punctuated equilibrium Species experience long periods of stasis Bursts of evolutionary change

58. Fig. 24-18a (a) The wild sunflower Helianthus anomalus

59. Fig. 24-20 (a) Typical Mimulus lewisii(b) M. lewisii with an M. cardinalis flower-color allele (c) Typical Mimulus cardinalis(d) M. cardinalis with an M. lewisii flower-color allele