BIO120H1 Lecture Notes - Allele Frequency, Chromosome

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11 Dec 2010
School
Department
Course
Lecture 6
Natural Selection
Key Concepts/ Terms:
Artificial selection
Heavy-metal tolerance
Stabilizing
Crop mimicry
Directional and disruptive selection
Herbicide resistant weeds
Industrial melanism
Heterostyly
1)Types of Selection: Artificial vs. natural, Modes of selection
2)Examples of selection: Evolution by pollution, Evolution in agriculture
Number One:
Natural selection can be defined as the differential survival and reproduction of genotypes in
response to factors in the environment. It can only occur when genotypes differ in fitness. Fitness is
measured by genotypes rate of increase relative to other genotypes in a population.
Artificial selection is sometimes used as a model for natural selection but there is a big difference,
natural selection has no purpose. For any given generation it results because of difference between
individuals with respect to their capacity to produce progeny. Natural selection is a self-generated
outcome of interactions between organisms and their environment. In contrast, artificial
selection is a purposeful process. It has a goal that can be visualized (eg. increase in yield) and a
selector humans. Both processes depend on heritable genetic variation.
Three basic modes of natural selection on quantitative traits are generally recognized. These are
stabilizing selection, directional selection, and disruptive selection.
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Document Summary

Key concepts/ terms: artificial selection, heavy-metal tolerance, stabilizing, crop mimicry, directional and disruptive selection, herbicide resistant weeds, heterostyly. Industrial melanism: types of selection: artificial vs. natural, modes of selection, examples of selection: evolution by pollution, evolution in agriculture. Natural selection can be defined as the differential survival and reproduction of genotypes in response to factors in the environment. It can only occur when genotypes differ in fitness. Fitness is measured by genotype"s rate of increase relative to other genotypes in a population. Artificial selection is sometimes used as a model for natural selection but there is a big difference, natural selection has no purpose. For any given generation it results because of difference between individuals with respect to their capacity to produce progeny. Natural selection is a self-generated outcome of interactions between organisms and their environment. In contrast, artificial selection is a purposeful process. It has a goal that can be visualized (eg. increase in yield) and a selector humans.

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