Version 8 Punctuated equilibrium in statistical models of ...
Punctuated Equilibrium
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Transcript of Punctuated Equilibrium
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Punctuated Equilibrium
Verses Gradualism
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What Drives Evolution
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1-Isolation
TemporalGeographicBehavioral
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2-Artificial Selection
Did not drive evolution!!!
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2-Natural Selection
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2-Natural Selection
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3-Variation & Heritability
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Sources of Genetic Variation
Mutations – 300 mutations in our DNA that are different from our parents mutations• Only matter if they can be passed to next generation – skin cancer
Sexual Reproduction – remixes the genes your parents provide into new combinations of paired alleles
Lateral Gene Transfer – only in single celled creatures but significant to all evolution and current resistance to drugs.
Single Gene (allele selection) Vs Polygenic Traits (phenotype selection) & how natural selection works on them.
Type of Selection for Polygenic Traits: Directional / Stabilizing / Disruptive
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Founder Population
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Bottleneck
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Genetic Drift
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Evolution Vs Genetic Equilibrium
Genetic Equilibrium = allele frequency in a gene pool does not change – sexual reproduction does not change change frequency.
Hardy Weinberg principle = predicts allele frequency for a population and if it is wrong than it is likely that evolution is taking place.
Disturbances to Equilibrium:1. Nonrandom mating – mate selection2. Small Population Size3. Immigration & Emigration4. Mutations5. Natural Selection6. Look at Darwin’s Finches pages 496-497
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Molecular Evolution
Molecular Clocks• Uses rates of neutral mutations in stretches of DNA to estimate the time that
two species have evolved independently of each other – page 499
Gene Duplication• Gene Families such as Hox genes• New copy genes evolve without changing the original
Hox Genes: Mutations to this gene is significant to the body plan
Dark Matter: Switches
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Microevolution & Macroevolution
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Mass Extinctions5 recorded mass extinctions1. Ordovician (440mya) - 50% of animal families2. Devonian (360mya) - 30% of animal families3. Permian (250mya) - 50% of animal families, including 95% of
marine species4. Triassic (210mya) - 35% of animal families5. Cretaceous (65mya) - 60% of animal species
Recovery Time6. Ordovician - 25 million years7. Devonian - 30 million years8. Permian/Triassic - 100 million years9. Cretaceous - 20 million years
Many other minor extinctionsBackground Extinction
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Mass Extinctions
Current - Holocene Extinction