Chapter 10: Population Genetics Biology Waggy
LEARNING OBJECTIVES 1. Define Population & gene pool 2. Discuss Relative Frequency & it’s role in Evolution 3. Differentiate between different types of Natural Selection & how they impact Evolution 4. Define Genetic Drift and how it can change a small population’s gene frequency 5. Explain how Genetic Equilibrium can block evolution and the required factors to do this 6. The Hardy-Weinberg Principle
LEARNING OBJECTIVE 1. Define population & gene pools
A population is a group of individuals of the same species that can interbreed and produce viable offspring.
Because members of a population interbreed, they share a common group of genes called a Gene pool A gene pool consists of all the genes present in a population, including all the different alleles (different versions of genes)
LEARNING OBJECTIVE 2. Discuss Relative Frequency & it’s role in Evolution
Relative Frequency The relative frequency is the number of times that an allele occurs in the gene pool compared to the occurrence of other alleles in the gene pool. Relative Frequency has nothing to do with whether an allele is dominant or recessive for example: In this population, the recessive allele is more frequent. Sample Population 48% heterozygous black 36% homozygous brown 16% homozygous black bb allele for black fur bb BB
in Genetic terms, Evolution is any change in the relative frequency of alleles in a population due to Natural Selection. If the relative frequency of the B allele in this mouse population changed over time to 30%, the population is evolving.
In real populations, phenotypic ratios are determined not only by which allele is dominant, but by frequency of the allele in the population When graphed, a bell shaped curve is typical of traits (& grades!)
So, the center of the bell curve is where fitness is stable, but on the outside edges, fitness varies, & this is where Natural Selection can act! Fitness is the ability of an organism to reproduce and for that offspring to make to reproductive age