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Published byGwendoline Dorsey Modified over 9 years ago
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Ch. 6: Evolutionary Processes/Outcomes
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Plants and Environment 1) Liebig (1840) –Law of the Minimum: Growth/distribution depends on environmental factor most limiting A Festive MoB CuMnZn Clapping Nicely
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Plants and Environment 2) Shelford (American: early 1900s) –Upper limits for factors –Proposed “Theory of Tolerance”
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Plants and Environment Phenotype: appearance Genotype: genetic make-up Phenotype: determined by genotype & environment
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Plants and the Environment Equation: V p = V g + V e V p = total phenotypic V g = variation due V e = variation due Focus V g
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Plants and the Environment Adaptation: –1) Genetically –2) With How determine trait adaptation? Hard! Genetic importance
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Plants and the Environment Genetic basis: Heritability (h 2 ): resemblance between relatives due h 2 = V g / V p –V g = variation due to –V p = total
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Plants and the Environment 1 approach: slope regression line (r 2 ) y = mx + b; m is slope r 2 =0 r 2 =0.52 r 2 =1
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Plants and the Environment Plant height ex. Fig. 6.3 (r 2 )=0.21 or 21% (h 2 )=0.21 or 21%
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Genetic Variation More better (generally) Why? –1) Raw material evolution (change genetic makeup) –2) Dominant alleles mask “lethal recessives:” fatal if Finish this sentence: If you were haploid you’d be __________________
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Genetic Variation Problem: genetic drift! Loss Small pop’ns Small population (9 inds.)Large population (50 inds.) Start: 50% mix 2 alleles
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Genetic Variation Ex, Wollemi “pine” (Australia)
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Loss of Genetic Variability Ex, Wollemi “Pine” (Australia) Extinct 2 mya, 2 groups found 1994. Discoverer David Noble Famous quote……
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Loss of Genetic Variability Ex, Wollemi “Pine” (Australia) No measurable genetic diversity! Collecting seeds by helicopter
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Genetic Variation Sources new genetic variation? –1) Mutation: Heritable. Rare: 10% of pop’n. each generation (new mutation) –2) Immigration.
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Plants and the Environment Recall: Adaptation: –1) Genetically determined trait –2) With survival or reproductive benefit How show benefit? Hard! Ex
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Adaptation Story Homoblasty = same twig/leaf forms
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Adaptation Story Homoblasty = same Different twig/leaf forms (plant age) = heteroblasty –Also called “juvenile” Ex, many Junipers (Juniperus)
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Adaptation Story Young plants (0-3 m tall) “divaricate” (wide-angled) Older (> 3 m): normal Pennantia corymbosa normaldivaricate
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Adaptation Story –Adaptation climate? –Adaptation herbivores (moas)? Plagianthus regius normal divaricate Moas?
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New Zealand’s Moas Ratites (Order) 11 species Giant moa leg bones Giant moa replica
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New Zealand’s Moas Hunted extinct by Maori
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Adaptation Story How study defense hypothesis? Other
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Adaptation Story Divaricate: 30-70% less loss Branches resist Divaricate
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Adaptation Story Non-native mammals not affected (shearing teeth) –Heteroblastic species declining
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Plants and the Environment Recall: Adaptation: –1) Genetically determined trait –2) With survival or reproductive benefit How show benefit? Hard!
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Variation due to Environment V p = V g + V e
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Variation due to Environment Phenotypic plasticity: vary form/physiology
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Variation due to Environment Ex, heterophylly: different –(“hetero”=other; “phyll”=leaf) Fig. 6.5 Emergent vs. Submerged leaves
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Species as ecological tool Now: species as tool Issues: –Species indicators –Plants adapt at –Revegetation/reforestation: does where
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Species Species def’n. –Species: Populations morphologically similar & –Biological species approach –Others: cladistics, etc.
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Species Good indicators: Ex, Quercus laevis (turkey oak). Dry sandy soils (sandhills)
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Species Bad indicators: widespread Differences genetic ( ?) or environmental ( ?) How evaluate? V p = V g + V e
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