Biology 2581B Lecture Notes - Lecture 9: Accelerated Evolution, Sex-Determination System, Sexual Reproduction
2 Feb 2018
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Document Summary
Mitosis only creates clones unless random mutation happens. (slow evolution) When earth rst existed (2 bya), organisms only reproduced by mitosis, and some still do today. About 1. 5 bya something evolved & cells were able to reproduce genetically variable o spring sexually leading to drastic evolution. Pace of evolution depends on amount of genetic variation. Sexual reproduction shu es genes & increases amt. of genetic variation > accelerated evolution. Sexual reproduction lead to the diversity we see today: consists of 2 parts: meiosis (1n) and fertilization (2n) In humans sex is determined by chromosomes (xx vs. xy) In some reptiles, sex is also chromosomal, but females have zw while males have. Sex can also be determined by the environment (ex: the temperature determines if a turtle egg hatches male/ female) Sex is either determined genetically or by environmental factors however, sex in bearded dragons is determined by both sex chromosomes and the temperature at which their eggs are incubated.
