BIOLOGY 1M03 Lecture Notes - Lecture 1: Genetic Drift, Stabilizing Selection, Directional Selection
24 Nov 2017
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Document Summary
Dirrectional selection tends to move a population in a particular dirrection, giraffe necks, human brains, multi directional selection can change through time with the environment. Some individuals reproduce more than others due to chance events: offspring receive certain parental allels and not others. Factors lead to accumalation of random changes in allel frequencies: example(blood types, drift is stronger in small populations than in large ones (law of averages, even if big now, may have been small in past. Large-scale evolution takes a long time: central question of biology, beneficial changes accumulatee gradually, much evidence of intermediate forms, what about sex, as an evolutionary process is very complicated. Still active debate on the advantages and disadvantages of sex: brings alleles together (and to split them apart, does not provide a source of new alleles, mating systems. Since relatives will tend to share similar alleles, inbred populations will tend to differ from hardy-weinberg equillibrium in what way: more homozygous loci.
