mechanisms for evolution
DESCRIPTION
MECHANISMS FOR EVOLUTION. Honors Biology. REVIEW. Evidence for Evolution and Examples What is Natural Selection? How did Darwin develop theory of Natural Selection?. PATTERNS OF EVOLUTION. Coevolution: 2 or more species evolve in association with one another - PowerPoint PPT PresentationTRANSCRIPT
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MECHANISMS FOR EVOLUTION
Honors Biology
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REVIEW
• Evidence for Evolution and Examples• What is Natural Selection?• How did Darwin develop theory of Natural Selection?
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PATTERNS OF EVOLUTION
• Coevolution:– 2 or more species evolve in association with one
another– Predators and Prey– Plants and Pollinators– Bats and Flowers
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PATTERNS OF EVOLUTION
• Convergent Evolution:– Organisms that look similar but are not related– Analogous features– Similar environments– Sharks and Dolphins
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PATTERNS OF EVOLUTION
• Divergent Evolution– 2 or more related populations or species become
more and more dissimilar – Usually a response to new habitat– Can result in new species– Adaptive radiation– Artificial Breeding– Humans and Chimps
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POPULATION GENETICS AND EVOLUTION
• What did Darwin know?– Environment is important– Competition for Resources– Natural Selection: Individuals with traits more
suitable for a particular environment are more likely to survive AND reproduce
• What did Darwin not know?– Where does variation come from
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POPULATION GENETICS
• We now know that variation comes from genetics; no variation extinction
• Population genetics: study of evolution from genetic point of view
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WHAT CAUSES VARIATION
• Need to think about variation in GENOTYPE– Mutation: change in DNA/chromosomes– Recombination: during meiosis– Random fusion of gametes
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OTHER MECHANISMS FOR EVOLUTION
• Things that upset genetic equilibrium• Using Hardy Weinberg you can predict
genotypes; Only in hypothetical populations
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MUTATION
• Change in DNA or chromosomes• Make new alleles for a trait• Many are harmful• Can be neutral (code for same amino acid)• Some are beneficial
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MIGRATION/GENE FLOW
• Call it gene flow• Populations exchange genes• Increases within group variation• Decreases between group variation• DOESN’T HAVE TO BE MIGRATION
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GENETIC DRIFT
• Occurs in small populations• Allele frequencies shift as a result of RANDOM
events• Coin Toss• Founders Effect; Bottleneck
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NONRANDOM MATING
• Sexual Selection• Positive assortative mating – mate with
someone similar• Negative assortative mating: redheads!
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NATURAL SELECTION
• Darwin and neoDarwinians believe is the most important way evolution occurs
• Types of Selection
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STABILIZING SELECTION
• Average form are selected for• Lizards:– Predators caught slow small and large visible– Select for medium size
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DIRECTIONAL SELECTION
• Individuals with an extreme trait are selected for
• Anteaters with long tongues
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DISRUPTIVE SELECTION
• Individuals with either extreme are selected for
• Limpet shell color; light and dark on different surfaces
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SEXUAL SELECTION
• Choosing mates based on traits• Intersexual Selection• Intrasexual Selection• Bird Color
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SPECIATION
• If enough changes accumulate new species• Biological concept of species: organisms can
mate and produce fertile offspring; not just morphological (what they look like)
• Isolating mechanisms speciation– Geographic isolation– Reproductive isolation
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SPECIATION
• Rates of speciation– Gradualism: species evolve gradually over time– Punctuated equilibrium: species go through times of fast change and slow or no change