BI111 Chapter Notes - Chapter 16: Microevolution
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16. 1a evolutionary biologists describe and quantify phenotypic variation: quantitative variation: individuals differ in small, incremental ways, often use the mean and variability to describe populations, natural selection changes the mean value of a character or its variability within populations, qualitative variation: exist in 2 or more discrete states, and intermediate forms are often absent, polymorphism: existence of discrete variants of a character (polymorphic traits, describe phenotypic polymorphisms quantitatively by calculating the percentage or frequency of each trait. 16. 1b phenotypic variation can have genetic and environmental causes: under some circumstances, individuals with different genotypes exhibit the same phenotype, organisms with the same genotype sometimes exhibit different phenotypes, only genetically based variation is subject to evolutionary change, mendel inferred the genetic basis of qualitative traits, such as flower colour in peas by crossing plants with different phenotypes, a population expressing quantitative traits that have genetic basis can be selectively bred to change the average value of the trait.
