Biol. 101 Notes

Biol. 101 Notes - ii. Ecological isolation – the whole...

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Genetic drift is a change in the gene pool based on chance not selection. Affects what type of population most severely? Small Two effects leading to genetic drift: both lead to a reduction in the variety of genes. 1. Bottleneck affect: a reduction in population size when individuals are randomly chosen. (ex. Flood or fire). 2. Founder effect: colonization of a new location by only a few individuals (chance as to who colonizes) Gene flow is when individuals or gametes are transferred between populations. Mutation is random change to a A. Ernst Mayr’s biological species concept: a group of population whose individuals have the potential to interbreed and produce fertile offspring. Species. B. Asexual and extinct organisms don’t fit in this concept: a. Morphological b. Genealogical c. Ecological C. Reproductive barriers – why can’t related species mate? a. Five pre-zygotic barriers and examples i. Temporal isolation – whole organism or gametes are not present at the same time.
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Unformatted text preview: ii. Ecological isolation – the whole organism or the gametes are not located in the same place. iii. Behavioral isolation – no sexual attraction iv. Mechanical isolation – unique reproductive parts v. Gamete mortality – copulation but no fertilization b. Post zygotic barriers i. Hybrid in-viability – no development of the embryo or you might develop offspring that are frail/weak ii. Hybrid sterility D. How do reproductive barriers form? Stop gene flow between 2 populations but mutation, natural selection, genetic drift act independently in each population. a. Allopatric speciation – “other homeland” physical or geographical barrier. i. Two species from one ancestral species = divergence ii. A burst of divergences from a single ancestor that least to many new species each adapted...
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This note was uploaded on 05/18/2011 for the course BIOL 101 taught by Professor Hogan during the Spring '08 term at UNC.

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Biol. 101 Notes - ii. Ecological isolation – the whole...

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