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Evolution (The Origin of Species (Hybrid: Offspring from 2 dif. species…
Evolution
The Origin of Species
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Models of Speciation
Punctuated Equilibria: Dramatic change to environment + ones that survive have weird characteristics that allows them to survive
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Fossils are evidence (little change, little change, then huge change)
Junk DNA contributes to speciation b/c we all have DNA we don't express but if an event occurs and only those with the rare DNA expressed survive they create speciation.
Darwinism
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Proof of Evolution
Direct Observations
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When species are introduced to a new environment, natural selection would favor those with traits suited to the environment
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Homology
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Convergent Evolution Distantly related organisms resemble one another b/c of the environment they share
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All life forms have almost the same genetic code suggesting that all species descended from a common ancestor (LUCA)
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Evolution of Populations
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Allele Frequencies
Natural Selection
Organisms in a population show variations in their trains that are better suited for the environment produce more offspring than those that don't
Adaptive Evolution: Traits that enhance survival or reproduction tend to increase in frequency over time
Selection results in alleles being passed to the next gen. in proportions that differ from those in present gen.
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Adaptive Evolution
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Selection
Directional Selection: Populations shift and favor one extreme (shifts pop. frequency curve) common when pop. migrates
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Sexual Selection
Sexual Selection: Ind. w/ certain inherited characteristics that are. desirable are more likely to reproduce
Sexual Dimorphism: Result of sexual selection w/ difference in secondary sexual characteristics between males/females
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Selection can only act on: existing variations, evolution is limited by historical constraints, adaptations are compromises