NATS 1940 Lecture Notes - Lecture 1: Frequency-Dependent Selection, Natural Selection 2, Genotype Frequency
14 Nov 2018
School
Department
Course
Professor
Document Summary
From question frequency of recessive allele is 0. 3 =q. Asked to find frequency of recessive trait = q2. = 0. 6 we need to find heterozygous frequency which is found by 2pq. Causes of evolution: natural selection, genetic drift. Discrete characters: either/or characters with distinct phenotype categories, variation of this type = qualitative variation, polymorphism = existence of qualitative variation (i. e. , different morphs) in a population. Eliminates individuals in one tail of the distribution. E. g. black bears: size increased during last ice age (larger body better heat retention); decreased again afterwards: stabilizing selection. Eliminates individuals in both tails of the distribution --> narrow. E. g. human infants with intermediate birth weight have highest survival rate: diversifying selection aka disruptive selection. Eliminates individuals in the middle of the distribution --> 2 peaks. Some individuals feed on large tough seeds --> thick beaks. Other individuals feed on small fiddly seeds --> thin beaks. Individuals with intermediate beaks poor at either strategy.
