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Adaptation
-heritable trait taht increases the fitness of an individual in a particular environment relative to those lacking the trait
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Natural Selection
- -ends with adaptation
- -NOT physiological (ex. warm weather, different genes turned on)
- Precondition:
- 1. must be a heritable variation in a population
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Modern Synthesis
- -1930-1940
- -argued that population processes (mutation, recombination, natural selection) account for the orgin of species
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Darwinian Evolution
- -change in genetic makeup of a poptulation over time
- -driven by natural selection
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Mutation
- -Incorrect replication: spontaneous
- -Chemical/radiation mutations: induced
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Mutation on DNA
-why?
-types
-nonsynonymous
-synonymous
- -mismatching DNA pairs.
- -proof reading andr repair enzymes help
- -not mutation until its stuck forever
- ex. substitution (transition-similar, transverson)
- -frameshift (deletion, insertion)
- -inversion (flipping 180)
- -reciprocal translocatoin (break DNA and reinsert somewhere else)
- nonsynonymous: change
- synonymous: no change
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mutation rate and natural selection
- -mutation in repair enzymes cause 100-1000x higer mutation rate
- -high mutation rate under changed conditions can be an advantage
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mutations on fitness
- -most lead to death
- -deleterious- incorrect protein, no protein, homeotic mutations
- -reduce by 2%
- -neurtral mutations- no effect on fitness, silent
- -positive
- -rare (ex. mutate to grow better at different conditions)
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obtaining new genes
-unequal crossing over
-transposable elements
-gene duplications
-chromosome mutations
-genome duplication
- -unequal crossing over: prophase, meiosis 1- lose gene
- -transposable elements: jumping genes
- -gene duplications: only need 1 to do function, other can mutate
- -chromosome mutations: inversion (ABCDE to ABEDC)
- -good evidence for natrual selection
- -genome duplication: may create new species, masive gene duplication
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mutation random
-respect to selective advantage
-respect to postion in genome
- selective advantage
- -yes, mutations do NOT occur due to need
- postion
- -no, mutational hot spots (due to unusual character)
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gene pool
- -total of all the alleles of a gene that occur in a population
- -same species = same genes
- -the alleles of these genes may vary
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phenotypic variation
- environment causes change in phenotype
- -ex coloring
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Hardy Weinberg
-equations
-circumstances
-conditions on which a population will NOT evolve
-within popluations (group of interbreeding individuals and thier offspring)
- -large populations with random mating, allele frequences remain constant
- -allele: p +q = 1
- -genotype: p2 +2pq + q2 = 1
- Population NOT to evolve:
- -no mutation
- -no migration
- -no natural selection
- -large population size
- -random mating
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Population genetic structure can change by
- -mutation
- -migration
- -natural selection: certain genotypes produce more offspring, causes divergence, leads to adaptation
- -genetic drift: due to chance alone
- -non random mating: interbreeding cause heterozygous to disapper and homo to appear
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genetic drift
-founder effect
- -isolated colonies are founded by a small number of individuals
- -allele frequences may be different than large group
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variation amount popluations of same species
- sympatric: populations overlap in distribution
- parapatric: adjacent populations
- allopatric: populations w/ isolated distributions
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clinal variation
change in character or allele frequencies over geographic distance
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fixed difference
on population having an allele and not the other popluation
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