Biology 1001A Lecture Notes - Lecture 11: Disruptive Selection, Genetic Variation, Qualitative Variation
25 Aug 2016
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In some populations, individuals vary in appearance, but members of most populations look alike. However, no one is identical i. e. differences in weight and height, anatomical features etc: phenotypic variation: differences in appearance or function among individuals of a population. If a difference is heritable, it is passed on through generations. Most characters i. e. colour exhibit quantitative variation: variation that is measured on a continuum (such as height in human beings) rather than in discrete units or categories. Quantitative variation is usually displayed in a bar graph: the width of the curve is proportional to the amount of variation, the mean describes the average value of a character. Qualitative variation: variation that exists in 2 or more discrete states, with intermediate forms often being absent: e. g. only blue or white feathers in snow geese. It is the phenotype, not genotype, that is successful or not.
