Biology Unit 1
Part 3 – Population Genetics
Name: ___________________________
Date ______________Pd: 1 2 6 7 8
Disruption of Genetic Equilibrium (pages 321-325)
One of the fundamental concepts for population genetics is stated
as follows:
For a very large, randomly mating population, the proportion
of dominant to recessive alleles remains constant from one
generation to the next – meaning the population is in genetic
In practical terms this means that, if a gene pool is to remain
unchanged, it must satisfy all of the criteria that favor gene pool
stability – no mutations, random mating, no gene flow, no natural selection and be a LARGE
population. The fact that FEW populations can be identified as meeting all (or any) of these criteria
means that they must be undergoing continual change in their genetic makeup.
For each of the five conditions shown below, define the terms. Then, state briefly HOW each would
affect the allele frequency in a gene pool. State whether the condition will increase or decrease
variation as well as which ones are ruled by chance.
1. Mutations:
2. Gene flow between populations:
Immigration –
Emigration -
3. Genetic Drift (Population size):
4. Sexual Selection:
5. Natural Selection:
Draw a graphical representation for each type of natural selection and explain the graph. Define
each type of natural selection and state its impact on variation.
Stabilizing selection:
Disruptive selection:
Directional selection:

Disruptions to Genetic Equilibrium 2013