Class Notes and Handouts for
Plant Biology 102

Plants, People and the Environment

Links of the Day:

Lecture 22. Genes by the bunch: Populations.

Some new concepts were introduced today that build on what I've already presented about simple Mendelian genetics. The main point made is that evolution will not occur without a change in gene frequencies in a population. To explore how gene frequencies change in the population, an overview was presented of the Hardy-Weinberg Law about genetic equilibrium and the conditions that must be met in order to have equilibrium. The four major conditions that cause gene frequencies to change in populations include: 1. Natural Selection; 2. Mutation Pressure; 3. Gene Flow; and 4. Genetic Drift. The links provided for today's lecture have well-written explanations of the major points made in class: Theories in Evolution and Population Genetics and the related link for Population Genetics of Monarch Butterflies; Random Genetic Drift (from Talk Origins Website); and Observed Instances of Speciation (also from Talk Origins; provides good explanations on species concepts and examples of speciation).

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Last updated February 17, 1999.