Lecture 27 Flashcards
Define fitness
Relative reproductive success of a genotype compared to other genotypes in the population; fitness ranges from 0-1
How do you calculate fitness?
Take the average number of offspring produced by a genotype and divide it by the mean number of offspring produced by the most prolific genotype
Define the selection coefficient and how to calculate it
Relative intensity of selection against a genotype; selection coefficient = 1-fitness for a particular genotype
Define directional selection
Selection in which one allele or trait is favored over another
Define overdominance (heterozygote advantage)
Heterozygotes are favored over homozygotes and have a reproductive advantage which maintains both alleles in the population
Define underdominance (heterozygote disadvantage)
Heterozygotes have a lower fitness than both homozygotes, which leads to an unstable equilibrium
What effect does mutations have on allelic frequencies in the short and long-term?
Short: change in allelic frequencies
Long: equilibrium reached between forward and reverse mutations
What effect does migration have on allelic frequencies in the short and long-term?
Short: change in allelic frequencies
Long: equilibrium reached when allelic frequencies of source and recipient population are equal
What effect does genetic drift have on allelic frequencies in the short and long-term?
Short: change in allelic frequencies
Long: fixation of one allele
What effect does natural selection have on allelic frequencies in the short and long-term?
Short: change in allelic frequencies
Long: directional selection; fixation of one allele; overdominant selection = equilibrium reached
underdominant selection = unstable equilibrium
Define evolution
Genetic change in a group of organisms (change in gene frequency in a population over time)
What is the concept of a phylogenetic tree?
Graphical representation of the evolutionary relationships among a group of organisms
Describe the molecular clock and rates of evolution
Molecular clock: rate at which a protein evolves is roughly constant over time; therefore, the amount of change that a protein has undergone can be used as a clock
What is the biological species concept?
Group of organisms whose members are capable of interbreeding with one another but are reproductively isolated from the members of other species; Ernst Mayr, 1942
Define anagenesis and cladogenesis evolution
Anagenesis: evolution taking place in a single group (lineage) with the passage of time
Cladogenesis: splitting of one lineage into two; new species arise