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Evolutionary Thought Timeline + Chap 9 and 10

Evolutionary Thought Timeline + Chap 9 and 10

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Evolutionary Thought Timeline + Chap 9 and 10

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  1. Evolutionary Thought Timeline+ Chap 9 and 10 Organisms Life Histories and Evolutionary Fitness

  2. Bit of review • Convergent Evolution -

  3. Convergence

  4. Convergence Theria Eutheria Metatheria ancestor

  5. Cactacea • Euphorbacea

  6. Adaptation • Pre-Darwinian idea • Old School Adaptation:

  7. a detour… Very brief history of evolutionary thought

  8. Evolutionary Thought Timeline • Wallace • Darwin Mid-late 1800s Process but not mechanism of inheritance “Evolution via natural selection” “Descent with modification” New Ideas?

  9. Some problems constraining the development of the theory • Lack of knowledge on age of Earth • “Species are fixed” constraint • Lack of scientific methodology • “Separate creation” constraint

  10. extant fossil fossil Time “specialization” ancestor Major Tenets of Darwin and Wallace • Evolution does occur • Change is gradual • Millions of species (fossil and extant) descended from a single ancestor • Primary process called Natural Selection

  11. Features of Evolution via Natural Selection • Population produces far more individuals than can survive. • Population has variability in most features • Features are heritable • Certain variants incur relative reproductive advantage

  12. Variation in heritable traits Elimination of certain variants Reproduction of survivors Result: increases the frequency of certain variants

  13. Gregor Mendel (1822-1884) • Monk / Gardener • Geneticist • Experiments with Plant Hybrids (- peas) • Provided mechanism of inheritance

  14. Theodosius Dobzhansky (1900-1975) • Russian geneticist • Lab evidence for natural selection (Drosophila) • (previous research was field observation based) • Architect of “Modern Synthesis” • Integration of genetics and evolutionary theory • Mutation – raw material for natural selection • Concerned with misuse of theory in society

  15. Ernst Mayr (1904-2005) • German training medical student – natural historian • Architect of “Modern Synthesis” • Integration of genetics and evolutionary theory • Isolating mechanisms and population level evolution (Biological species concept)

  16. George Gaylord Simpson (1902-1984) • Paleontologist • Architect of “Modern Synthesis” • Fossil record lends evidence to theory of Darwin and Wallace. • Evolution is not on a predetermined, directed path.

  17. Adaptation • Old School – evolutionary process by which organisms become better suited to environment • New School – genetically determined characteristic that enhances the ability of an individual to cope with its environment.

  18. Velvet mite

  19. Life History Notes • Mojave Desert • Burrow in sand • Main food source: • Grounded termites • Termite “fall-out” • Moderate temperatures • 1st sunny day after a rain (>8mm)

  20. Daily Migration

  21. yes Breed Find Mate? ♀ yes Emerge from burrow ♂ yes Termite fall-out? no Favorable Conditions? Lay eggs Stay in burrow no no Burrow

  22. The cost of making a wrong decision. • Emerge at wrong time: • No food – can lead to death • No mate – can lead to reduced RO • No herd effect – can lead to death via predation Those variations of the population become rare IOW – Big cost to making wrong decision.

  23. Migrant birds • Migration is energy demanding: • Staging areas to fatten up. • If no, then fail. • The “bad weather versus predator avoidance” trade-off • Bad weather: • Fatten-up to survive until better conditions • Predator avoidance • Requires maneuverability – proportional to lean body mass. • The choice: • Fatten up? Payoff prior to bad weather or season. • Remain lean? Payoff during times of high predation risk.

  24. Features of Evolution via Natural Selection • Population produces far more individuals than can survive. • Population has variability in most features • Features are heritable • Certain variants incur relative reproductive advantage • Fitness is one component of big picture

  25. Fitness • Fitness: • Generic: • Genetic: • Genotype: • Phenotype: VP = VG + VE + VGxE Variation in population

  26. G Natural Selection acts here – random? Tall gene Short gene int. tallest Good nutrition E int. shortest Poor nutrition Loci for different genes VP = VG + VE + VGxE Alleles – different genetic information for same gene A type – produces Enzyme “A” B type – produces Enzyme “B” O type – produces no enzyme

  27. B A Alleles – genetic variability in the population Allelic variation arises from MUTATION Central Dogma: DNA  RNA  Protein m

  28. Mutation • Stochastic changes in genetic material • Caused by: • Internal • Misrepair of DNA • Misreading of DNA by RNA • External (Environmental) • http://www.evol.nw.ru/labs/lab38/spirov/hazard/mutagen_lst.html • Radiation (UV) • Most are harmful or “neutral” • Provides palette for Natural Selection Not-random

  29. Select

  30. 1 example of selection leading to evolution Citrus Scale in California

  31. Evolution of sexual preference in Drosophila

  32. …Back to VP • Even though there is variability in the phenotype, there is still only a particular range of environmental conditions that any given organism (or population) can occupy • Organism – unit of natural selection • “Activity Performance Space” • Population – unit of evolution • “Distribution”

  33. Thermo-tolerance graph (warm-blooded orgs) • “Activity Performance Space” (Resource utilization curve) – the “optimum” environmental conditions…

  34. Desert Iguana Regulation of temp Time spent at each location varies throughout year

  35. Microhabitat selection favors “optimum” conditions -

  36. Cactus Wren

  37. Figure 9.8

  38. Figure 9.7