BILD 3 Lecture Notes - Lecture 15: Adaptive Radiation, Allele Frequency, Species Ii
30 May 2016
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1. how do species arise: evolutionary processes and speciation a. i. a. ii. a. iii. a. iv. If the environments differ, natural selection will change allele frequencies differently in each population (adaptation) a. v. Genetic drift will result in the fixation and loss of different alleles in the population: allopatric speciation (much more common) a. i. a. ii. a. iii. 2. allopatric speciation: reproductive isolation occurs because populations are geographically separated either by vicariance or dispersal, vicariance a. i. a. ii. a. ii. Closed 3 million years ago when a land bridge formed between n and s. Divergence of two populations due to a physical barrier. Marine organisms separated when the land bridge formed. Species occur on both sides of the isthmus a. i. 2. If the land bridge isolated populations of an ancestral species, then for that species their closes relative should be on the other side of barrier a. ii. Phylogeny of snapping shrimp based on dna data a. i. 1.
