Lecture #11 Date ________

1. Lecture #11 Date ________ • Chapter 24 ~ The Origin of Species

2. Today • Look at the definition of species • How do new species arise • What are ways organisms can be reproductively isolated • Allopatric vs sympatric speciation • Gradualism vs punctuated equilibrium

3. Reminder • Ch. 23 and 24 Quiz – tomorrow • Test – Tuesday • Labs due on Tuesday

4. Macroevolution: the origin of new taxonomic groups • Speciation: the origin of new species • Microevolution – a change in allelic frequencies (p and q) within a population over time • Macroevolution – broad pattern of evolution over long periods of time (involves speciation)

5. What is a species? • Biological species concept (Mayr):a population or group of populations whose members have the potential to interbreed and produce viable, fertile offspring (genetic exchange is possible and that is genetically isolated from other populations)

6. Other definitions of species • Morphological – can include asexual organisms • Ecological • Phylogenetic

8. When 2 organisms from different species interbreed, hybrids are created.

13. Reproductive Isolation (isolation of gene pools), I • Prezygotic barriers:impede mating between species or hinder the fertilization of the ova • Habitat (snakes; water/terrestrial) • Behavioral (fireflies; mate signaling) • Temporal (salmon; seasonal mating) • Mechanical (flowers; pollination anatomy) • Gametic (frogs; egg coat receptors)

14. Videos

16. Reproductive Isolation, II • Postzygotic barriers: fertilization occurs, but the hybrid zygote does not develop into a viable, fertile adult • Reduced hybrid viability (frogs; zygotes fail to develop or reach sexual maturity) • Reduced hybrid fertility (mule; horse x donkey; cannot backbreed) • Hybrid breakdown (cotton; 2nd generation hybrids are sterile)

17. Liger

18. Zebroid

19. Zonkey

20. Zetland

21. Beefalo

22. Geep

23. Leopon

24. Cama

25. Pumapard

26. Ocelot/Puma

27. Jaglion

28. How do new species arise?

29. Modes of speciation (based on how gene flow is interrupted) • Allopatric:populations segregated by a geographical barrier; can result in adaptive radiation (island species) • Sympatric:reproductively isolated subpopulation in the midst of its parent population (change in genome); polyploidy in plants; cichlid fishes

32. Speciation • Allopatric speciation – geographic isolation

35. Cline – a graded change in a character along a geographic axis • Along a mountainside (changing temperature, elevation, precipitation) • In aquatic environments (changing temps., pressure, O2 concentration)

36. Allopatric speciation • http://wps.prenhall.com/esm_freeman_biosci_1/7/1951/499633.cw/index.html

37. Sympatric speciation – polyploidy in plants, habitat differentiation (clines), sexual selection

39. Autopolyploidy

40. Allopolyploidy

41. Sympatric Speciation • http://bcs.whfreeman.com/thelifewire/content/chp24/2402001.html

42. Hybrid Zones • Reinforcement – hybrids are less fit • Fusion – gene pools become similar (cichlids) • Stability – continued production of hybrid individuals

44. Patterns of evolution

45. Punctuated equilibria • Tempo of speciation: gradual vs. divergence in rapid bursts; Niles Eldredge and Stephen Jay Gould (1972); helped explain the non-gradual appearance of species in the fossil record

46. Adaptive Radiation/Mass extinctions

47. Divergent evolution / homologous structures

48. Convergent evolution /Analogous Structures

49. Review • Definition of species/speciation • Isolating mechanisms • Allopatric vs sympatric speciation • Convergent vs divergent evolution • Gradualism vs punctuated equilibrium

50. Review Topics • 6 Groups • Ch. 22, 23, and 25 – 2 groups per chapter • Important vocabulary • Possible essay topics