LIFESCI 1 Lecture Notes - Lecture 9: Noncoding Dna, Genome Size, Phylogenetic Tree
21 Jan 2015
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Genetic drift and selection: in small populations, genetic drift can overpower selection, so counterintuitively: deleterious variants can be fixed, figure: small mutation, slightly deleterious, negative selection coefficient (-0. 01) means it is harming fitness, allele frequency over time. Larger population (500) within about 400 generations, the deleterious allele is lost. Smaller population (50) one of the allele is fixed, others are on their way to becoming fixed: so in small populations, deleterious mutations are more likely to become fixed. Demonstrating adaptation: a major focus of evolutionary biology: to prove adaptation: requires careful development of a hypotheses and careful testing. Show that individuals possessing the trait leave more offspring than those that do not: 3. ) Show that trait was shaped by natural selection to serve the same primary function that makes it beneficial today. In the first treatment, no significant difference. In the second treatment, tick load decreased without oxpeckers.
