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ANTA01 - Day 2.docx

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University of Toronto Scarborough
Mary Silcox

September 16, 2013 ANTA01 – Day 2 Evolution  “Descent with modification” (Darwin, 1859) – change between generations, through time  “A change in genetic structure of a population from one generation to the next.” (Lewis et al., p. 2)  Three different processes:  Processes of evolution  Timescale of evolution  Genetics Adaption: a feature of an organism that increases the likelihood of its survival and reproduction in a particular environment Adaptive radiation: the evolution of multiple divergent species from a single less specialized ancestral species Niche: the role of a species in its environment, everything it does, interacts with Basic Tenets of natural selection a) Variation exists – not everybody is the same b) That variation is heritable – tall people tend to have tall babies. Things that are distinctable are often passed on c) Some variants are better adapted to deal with their environment than others – some polar bears may have thicker coats than other polar bears may be due to climate d) If left unchecked, every organism will produce more offspring than can survive – every organism has more potential to reproduce that the environment can sustain e) More offspring of the better adapted variants will survive – polar bears with thick fur coats will more likely to survive f) These offspring will have the adaptions of their parents – the whole population will change after enough years g) Over time, this will lead to a change in the population resemble the better adapted vairants h) Over a long enough time frame, this will produce large scale changes, including speciation Evolutionary Processes Selection:  Natural selection  There is no selecting agent  Purely up to survival  Artificial selection  Selected by particular variants September 16, 2013  Sexual selection  Non-random mating, inbreeding  Selection on features or behaviours associated with mating  Generally takes two forms 1. Male-male competition: bighorn sheep head butting for a mate 2. Female choice: female bower bird inspecting a bower  Sperm is cheap: females are the selective factor  Humans use variables to choose mating partner like: religion  Charles II of Spain (the Bewitched)  Exhibits a feature called the Hapsburg Jaw  An outslung lower jaw  Had difficulty choosing his food, and mentally retarded  An instance of cultural differences Mutation  “a change in DNA… can refer to changes in DNA bases as well as changes in chromosome number or structure” Lewis et., . 42  Only important to evolution if they occur in sexcells  The ultimate source of all variation  Sickle-cell anemia: point mutation Genetic Drift  Gamete sampling: changes in the genetic material passed on to the next generation just as a result of random chance in which variants get passed on*  Fission/Fission effect: changes in the frequency of variants in a population as a result of subdivision – lead to speciation  Founder effect: differences in the frequency of variants in a population as a result of random chance in which members start a new population  One outcome of founder effect can be an increase in the relative frequency of a rare type ( a gene for a disease such as porphyria)  Outbreak srat in 1680s  Jansz, one or both, carried the gene for porphyria  There is more a significant amount of white people in South Africa that have this disease  Those who do have it, can be traced back to the Jansz  Evolutionary bottlenecks: a restriction in genetic variability with a decrease in population size  Random chance  cheetas Gene flow  exchange of genes between populations … 62 September 16, 2013  has the effect of making populations more s
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