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Ch. 6: Evolutionary Processes/Outcomes

Ch. 6: Evolutionary Processes/Outcomes. Plants and Environment. 1) Liebig (1840) Law of the Minimum : Growth/distribution depends on environmental factor most limiting. A Festive MoB CuMnZn Clapping Nicely. Plants and Environment. 2) Shelford (American: early 1900s) Upper limits for factors

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Ch. 6: Evolutionary Processes/Outcomes

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  1. Ch. 6: Evolutionary Processes/Outcomes

  2. Plants and Environment • 1) Liebig (1840) • Law of the Minimum: Growth/distribution depends on environmental factor most limiting A Festive MoB CuMnZn Clapping Nicely

  3. Plants and Environment • 2) Shelford (American: early 1900s) • Upper limits for factors • Proposed “Theory of Tolerance”

  4. Plants and Environment • Phenotype: appearance • Genotype: genetic make-up • Phenotype: determined by genotype & environment

  5. Plants and the Environment • Equation: • Vp = Vg + Ve • Vp = total phenotypic variation • Vg = variation due to genotype • Ve = variation due to environment Focus Vg

  6. Plants and the Environment • Adaptation: What is an adaptation?

  7. Plants and the Environment • Adaptation: • 1) Genetically determined trait • 2) With survival or reproductive benefit • How determine trait adaptation? Hard! Genetic importance

  8. Plants and the Environment • Genetic basis: • Heritability (h2): resemblance b/w relatives (shared genes) • h2 = Vg / Vp • Vg = variation due to genotype • Vp = total phenotypic variation

  9. Plants and the Environment • 1 approach: slope regression line (r2) y = mx + b; m is slope r2=0.52 r2=0 r2=1

  10. Plants and the Environment • Plant height ex. (r2)=0.21 or 21% (h2)=0.21 or 21% Fig. 6.3

  11. Genetic Variation • More better (generally) • Why? • 1) Raw material evolution • 2) Dominant alleles mask “lethal recessives:” Finish this sentence: If you were haploid you’d be __________________

  12. Genetic Variation • Problem: genetic drift! Start: 50% mix 2 alleles Small population (9 inds.) Large population (50 inds.)

  13. Genetic Variation • Ex, Wollemi “pine” (Australia)

  14. Loss of Genetic Variability • Ex, Wollemi “Pine” (Australia) • Extinct 2 mya, 2 groups found 1994. 40 plants! Discoverer David Noble Famous quote……

  15. Loss of Genetic Variability • Ex, Wollemi “Pine” (Australia) • No measurable genetic diversity! Collecting seeds by helicopter

  16. Genetic Variation • Sources new genetic variation? • 1) Mutation: Heritable change • 2)

  17. Plants and the Environment • Recall: • Adaptation: • 1) Genetically determined trait • 2) With survival or reproductive benefit • How show benefit? Hard! Ex

  18. Adaptation Story • Homoblasty = same

  19. Adaptation Story • Homoblasty = • Different • = heteroblasty • Also called “juvenile” foliage • Ex, many Junipers (Juniperus)

  20. Adaptation Story • Field trip: New Zealand! • 20% trees heteroblastic

  21. Adaptation Story • Young plants (0-3 m tall) “divaricate” ( • Older (> 3 m): normal Pennantia corymbosa normal divaricate

  22. Adaptation Story • Adaptation climate? • Adaptation herbivores (moas)? normal divaricate Plagianthus regius Moas?

  23. New Zealand’s Moas • Ratites (Order) • 11 spp. Giant moa leg bones Giant moa replica

  24. New Zealand’s Moas • Hunted extinct by Maori

  25. Adaptation Story • How study defense hypothesis?

  26. Adaptation Story • Divaricate: 30-70%

  27. Adaptation Story • Non-native mammals not affected (shearing teeth) • Heteroblastic spp. declining

  28. Plants and the Environment • Recall: • Adaptation: • 1) Genetically determined trait • 2) With survival or reproductive benefit • How show benefit? Hard!

  29. Variation due to Environment • Vp = Vg + Ve

  30. Variation due to Environment • Phenotypic plasticity: vary form/

  31. Variation due to Environment • Ex, heterophylly: different leaf • (“hetero”=other; “phyll”=leaf) Emergent vs. Submerged leaves Fig. 6.5

  32. Species as ecological tool • Now: sp. as tool • Issues: • Sp. indicators environmental conditions? • Plants adapt at sp. level? • Revegetation/reforestation: does where we obtain plants matter?

  33. Species • Species def’n. • Species: Populations • Biological species • Others: cladistics, etc.

  34. Species as ecological tool • Issues: • Sp. indicators environmental conditions? • Plants adapt at sp. level? • Revegetation/reforestation: does where we obtain plants matter?

  35. Species • Good indicators: Ex, Quercus laevis (turkey oak).

  36. Vp = Vg + Ve Species • Bad indicators: widespread & variable • Differences • How evaluate?

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