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Development of New Species by Evolution
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What is Speciation? It can occur when members of a population become isolated from each other. Once two populations are reproductively isolated, they are considered separate species. Speciation is the evolution of 1+ species from a single ancestor species.
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Allopatric Speciation (Geographic Isolation)
A physical barrier (continental split, rise in sea level, formation of mountain range, advance of glacier, change in habitat) prevents gene flow between populations of a species
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Sympatric Speciation A process through which new species evolve from a single ancestral species while inhabiting the same geographic region.
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Behavioral Isolation Two populations are capable of interbreeding, but have differences in courtship rituals or other reproductive strategies.
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Temporal Isolation Species reproduce at different times.
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Speciation in Darwin’s Finches
Speciation in the Galapagos finches occurred by: Founding of a new population Geographic isolation Changes in new population’s gene pool Reproductive isolation Ecological competition
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Evolution does not occur in a set direction
Evolution builds on what already exists, so the more variety there is, the more there can be in the future. However, evolution does not necessitate long-term progress in a set direction.
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Rate of Evolution Gradualism - theory that new species evolve as the genomes of two populations differentiate over time. Punctuated equilibrium - theory that populations remain genetically stable for long period of time, interrupted by brief periods of genetic change.
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Mechanisms of Evolution
Divergent Evolution - when isolated populations of a species evolve independently. Convergent Evolution -occurs when Natural Selection has produced similar adaptations in response to similar environment between different species.
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Coevolution Species that interact closely often adapt to one another in a process called coevolution.
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Adaptive Radiation Adaptive Radiation is the evolution of many diversely adapted species from one common ancestor. It usually occurs on an isolated island. Ex. Darwin’s finches
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Patterns of Evolution
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