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Lecture

Biol 121- 2010.03.12- Evolution- Natural Selection (Ch. 24)..
Biol 121- 2010.03.12- Evolution- Natural Selection (Ch. 24).docx

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School
University of British Columbia
Department
Biology
Course
BIOL 121
Professor
Carol Pollock
Semester
Winter

Description
Biol 121 225 Freeman 491500Mar 12 10Natural Selection Ch 24 Natural selection credit for natural selection is given to Darwin first proposed by Lamarck and others had already proposed evolution as a pattern in nature used to explain before Darwin began his work but Darwin had the crucial insight of seeingnatural selection that could be used to explain pattern of descent withmodification four simple postulatessteps 1 Variation in a pop Individual organisms that make up a pop vary in traits they possess like size or shape 2 Heritable traits involvedSome trait differences are heritable so passed on to offspring genetically 3 Variable fitnessIn each generation many more offspring are produced than can possibly survive therefore only some individuals in the pop survive long enough to produce offspring and among individuals that produce offspring some produce more than others 4 Fitness due to heritable traitsSubset of individuals that survive best and produce the most offspring is not a random sample of the pop individuals with certain heritable traits are more likely to survivereprod natural selection occurs when indiv with certain char produce more offspring than do indiv wo those characteristics The outcome of these four steps Evolutionchange in genetic char of a pop over time is the outcome of these four steps variation among individuals is necessary for evolution populations must change over time for evolution to occur Summing up the 4 steps in only 2 Evolution by natural selection occurs when 1 heritable variation leads to 2 differential success in survival and reproduction Allele frequencies WRT evolution evolution can be d
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