1 / 49

Chapter 19: Speciation and Macroevolution

Chapter 19: Speciation and Macroevolution. Biological Species Concept. Species consist of 1+ populations whose members are capable of interbreeding in nature to produce fertile offspring and do not interbreed with members of different species Sexual reproduction Reproductive isolation.

keely
Download Presentation

Chapter 19: Speciation and Macroevolution

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Chapter 19: Speciation and Macroevolution

  2. Biological Species Concept • Species consist of 1+ populations whose members are capable of interbreeding in nature to produce fertile offspring and do not interbreed with members of different species • Sexual reproduction • Reproductive isolation

  3. Fig. 24-2 (a) Similarity between different species (b) Diversity within a species

  4. Reproductive Isolating Mechanisms • Prevent interbreeding between 2 species • Preserve genetic integrity • Gene flow is prevented

  5. Reproductive barriers - prezygotic • Prezygotic – prevent fertilization • Interspecific zygote never made • Types: • Temporal • Habitat • Behavioral • Mechanical • gametic

  6. Temporal • Different times • Day, season, year • Ex: • Fruit flies – afternoon vs. morning • Frogs – late March vs. mid-April

  7. Fig. 24-4e (c) Eastern spotted skunk (Spilogale putorius)

  8. Fig. 24-4f (d) Western spotted skunk (Spilogale gracilis)

  9. Habitat • Same geographical area, different habitat • Ex: • Flycatchers • Open woods/farms • Deciduous forest • Wet thickets • Coniferous forest • Brushy pastures/ willow thickets

  10. Fig. 24-4c (a) Water-dwelling Thamnophis

  11. Fig. 24-4d (b) Terrestrial Thamnophis

  12. Behavioral • Courtship (signals before mating) • Aka “sexual isolation” • Ex: • Nest decoration, dance, song, vocalizations

  13. Fig. 24-4g (e) Courtship ritual of blue- footed boobies

  14. Mechanical • Incompatible structures of genital organs • Ex: • Flowers adapted for different insect pollinators

  15. Fig. 24-4h (f) Bradybaena with shells spiraling in opposite directions

  16. Gametic • Egg and sperm incompatible after mating • Ex: • Aquatic animals – release egg and sperm at once; egg and sperm protein bind to each other

  17. Fig. 24-4k (g) Sea urchins

  18. Reproductive barriers - Postzygotic • Prevent gene flow when fertilization occurs • Hybrid inviability • Hybrid sterility • Hybrid breakdown

  19. Fig. 24-4l (h) Ensatina hybrid

  20. Hybrid inviability • Increased likelihood of reproductive failure after fertilization • Spontaneous abortion – genes do not interact properly

  21. Hybrid sterility • Interspecific hybrid lives but can’t reproduce • Incompatible courtship w/ either parent species • Gametes of hybrid abnormal during meiosis • Different chromosome #’s • Female horse – 64 • Male donkey – 62 • Mule - 63

  22. Fig. 24-4m (i) Donkey

  23. Fig. 24-4n (j) Horse

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

  25. Hybrid breakdown • Inability of a hybrid to reproduce due to some defect • F2’s • Ex: • 2 sunflower species – 80% F2 can’t reproduce

  26. Fig. 24-4p (l) Hybrid cultivated rice plants with stunted offspring (center)

  27. Reproductive isolation is the Key to Speciation • Speciation = evolution of a new species • 2 patterns • 1) Anagenic • 2) Cladogenic

  28. Anagenesis • (phyletic evolution) • Relatively small, progressive evolutionary changes in a single lineage over long periods • Enough time  conversion of 1 species to another • Sequence of species occurs over time without an increase in the number of species

  29. Cladogenesis • (branching evolution) • 2+ populations of an ancestral species split and diverge, eventually forming 2+ new species • Clade = cluster of species derived from a single common ancestor • Over time  increase species richness

  30. When has speciation occurred? • Population is sufficiently different from its ancestral species that no genetic exchange can occur between them • 2 ways: • Allopatric • Sympatric

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

  32. Allopatric Speciation • Occurs when 1 population becomes geographically separated from the rest of the species and then evolves by natural selection and/or genetic drift • Most common • Geographic isolation by: • Changing of Rivers, glaciers, mountains, land bridges, lakes • Birds vs. rats • Small population migrates or is dispersed • Colonize new area • Isolated gene pool  microevolution  new species

  33. Fig. 24-6 A. harrisi A. leucurus

  34. Sympatric Speciation • New species evolves within the same geographical region as the parent species • 2 ways: • Change in • Ploidy • Ecology

  35. Ploidy • Polyploidy - 2+ chromosome sets • Plants – rapid speciation • Autopolyploid – multiple sets chromosomes from a single species • Allopolyploidy – multiple sets of chromosomes from 2+ species • Allopolyploid – diff # chromosomes from parents = new species • 1) extinct • 2)coexist • 3)replace parent species

  36. Fig. 24-10-3 2n 2n = 6 4n = 12 4n Failure of cell division after chromosome duplication gives rise to tetraploid tissue. Gametes produced are diploid.. Offspring with tetraploid karyotypes may be viable and fertile.

  37. Fig. 24-11-4 Species B 2n = 4 Unreduced gamete with 4 chromosomes Unreduced gamete with 7 chromosomes Hybrid with 7 chromosomes Meiotic error Viable fertile hybrid (allopolyploid) 2n = 10 Normal gamete n = 3 Normal gamete n = 3 Species A 2n = 6

  38. Allopatric and Sympatric Speciation: A Review • In allopatric speciation, geographic isolation restricts gene flow between populations • Reproductive isolation may then arise by natural selection, genetic drift, or sexual selection in the isolated populations • Even if contact is restored between populations, interbreeding is prevented

  39. In sympatric speciation, a reproductive barrier isolates a subset of a population without geographic separation from the parent species • Sympatric speciation can result from polyploidy, natural selection, or sexual selection

  40. Ecology • Parasitic insects • Ex: fruit maggot flies • Switched host from hawthorn tree fruits to domestic apples • Mutation  disruptive selection  different ecological opportunity

  41. Evolutionary Change – rapid or gradual?2 models • Punctuated Equilibrium – fossil record accurately reflects evolution as it actually occurs • Long periods of stasis are punctuated by short periods of rapid speciation triggered by changes in the environment • Speciation in “spurts” • Short periods evolution, long periods stability • Accounts for abrupt appearance of new species with few intermediate forms

  42. Fig. 24-17 (a) Punctuated pattern Time (b) Gradual pattern

  43. Gradualism – traditional view of evolution • Evolution proceeds continuously over long periods • Rarely observed, fossil record incomplete • Populations slowly diverge from 1 another by the gradual accumulation of adaptive characteristics within each population

  44. Macroevolution • Dramatic changes that occur over long time spans in evolution • Attempts to explain large phenotypic changes (novelties) • Important aspects • Evolutionary novelties • Adaptive radiation • Mass extinction

  45. Macroevolution

  46. Adaptive radiation • Evolutionary diversification of many related species from 1 or a few ancestors in a short period • Adaptive zones: new ecological opportunities that were not exploited by an ancestor • Islands – common – fewer species there • Ex: Darwin’s finches, honeycreeper birds, silversword plants

  47. Extinction • End of lineage; last member of species dies • Permanent • Makes adaptive zones vacant • Background extinction • Continuous, low-level • Mass extinction • Numerous species die at once • Adaptive radiation follows

  48. Extinction video • Causes of mass extinction • Climate change / Earth’s temp. • Catastrophes • Comet/asteroid  dust (block light)  food chain disrupted, drop in temp. • Competition • Humans  animal / plant habitats

  49. Microevolution vs. Macroevolution Chance events “lucky” to survive Right place, right time • Genetics • Well suited survive

More Related