lecture13 - BioEE 278 Evolutionary Biology Fall 2007...

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BioEE 278 Fall 2007 Evolutionary Biology Lecture 13 NATURAL SELECTION WHAT IS IT AND WHAT HAPPENS WITHOUT IT? TEXT READING: Ch. 9, pp. 192-197; Ch. 11, pp. 247-252 SECTION – Oct 16-18 Due : Hardy Weinberg problems from lecture (see below) Activity: Artificial selection experiment. Read handout before section! Write-up of exercise will be due in section Oct 25-27. A. Goal of the study of “Micro-Evolution” 1. Understanding the processes of evolutionary change in populations 2. How do these processes account for the amount and distribution of genetic variation within and between populations? 3. How does divergence among populations contribute to the origin of diversity at higher taxonomic level? B. Natural Selection as the Process of Modification of Wild Species 1. Evolution by natural selection results is the following conditions are met: a. Necessary conditions for the evolution by Natural Selection. Individuals vary in survival, mating, and fertility, such that some have more offspring than others. Individuals in a population vary for some character(s). Variation in offspring production is related to variation in characters states (phenotypes). Phenotypes are at least partially heritable – genetically based – such more successful variants pass on more copies of their alleles than less successful ones. The frequencies of these beneficial alleles and genotypes increase over time. b. Example of evolution by natural selection: alpine skypilot 2. How does natural selection differ from artificial selection? a. In artificial selection all of the conditions above must be met, except that it is humans who choose the desirable phenotypes instead of the natural environment being the “filter” on who is successful and who is not. b. Example of evolution by artificial selection c. Evolution by natural selection is a “passive” process— there is no active “force” guiding the course of evolutionary change -- whereas artificial selection is an “active” process, with humans directing the course of evolution. d. Darwin arrived at the theory of natural selection from having seen the results of artificial
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lecture13 - BioEE 278 Evolutionary Biology Fall 2007...

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