Biology 1201A Lecture Notes - Lecture 16: Snow Goose, Genotype Frequency, Allele Frequency
4 Jan 2018
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Phenotypic variation- differences in appearance or function that- if based on heritable information-are passed from generation to generation (ex. differences in mass, length, diameter in a population that look pretty much alike) 16. 1a evolutionary biologists describe and quantify phenotypic variation. Most characters exhibit quantitative variation- individuals differ in small, incremental ways (ex. weight in a class) Display data on bar graph or curve (width of curve is proportional to the variability, mean describes average value of the character) Natural selection often changes the mean value of a character or its variability within populations. Other characters exhibit qualitative variation- they exist in two or more discrete states, and intermediate forms are often absent. The existence of discreet variants of a character is called a polymorphism. We describe phenotypic polymorphisms quantitatively by calculating the percentage or frequency of each trait. 16. 1b phenotypic variation can have genetic and environmental causes.
