1. Origin of Species Chapter 24

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

5. Speciation One species gives rise to many descendant species

6. Galápagos giant tortoise, another species unique to the islands

7. 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

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

10. 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

11. Species Homo sapiens Diversity Belong to same species Capacity to interbreed.

12. Species Species are based on inter-fertility, Not physical similarity. Eastern & western meadowlarks Have similar shapes & coloration Differences in song prevent interbreeding between species.

13. Reproductive isolation Members of a population Cannot mate Or produce fertile offspring What causes reproductive isolation? What helps species to retain their identities?

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

15. Prezygotic barriersPostzygotic barriers Habitat isolation Temporal isolation Behavioral isolation Mechanical isolation Gametic isolation Reduced hybrid viability Reduced hybrid fertility Hybrid breakdown Indivi- duals of differen t species MATING ATTEMP T FERTILI - ZATION VIABLE, FERTILE OFF- SPRING (l)(i) (j) (h)(g)(f)(e)(c) (a) (b) (d) (k)

16. Prezygotic isolating mechanisms 1. Ecological (Habitat) isolation 2. Behavioral isolation 3. Temporal isolation 4. Mechanical isolation 5. Gamete isolation

17. 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

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

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

20. Behavioral isolation Blue-footed boobies Courtship dance

22. Behavioral isolation Pheromones: Chemical signals used when mating Lacewings: Move their abdomen to create a mating song Varies among species

23. 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

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

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

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

27. 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

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

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

30. 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

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

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

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

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

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

36. Antelope squirrels

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

38. Allopatric speciation Hawaiian Islands

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

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

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

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

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

44. Polyploidy

45. Hugo de Vries---primrose

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

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

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

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

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

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

53. Gene flow Population Barrier to gene flow Isolated population diverges. Hybrid zone Hybrid individual Possible outcomes: Stability Fusion Reinforcement

54. Grizzly bear (U. arctos) ▶ ▶ Polar bear (U. maritimus) Hybrid “grolar bear” ▶

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

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

57. Gradualism

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

59. Punctuated equilibrium

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