a selective pressure
Driving Question 3:
How does the gene pool of an evolving population compare to the gene
pool of a nonevolving population?
Why should you care?
In early 1908, two mathematicians (G.H. Hardy and Wilhelm Weinberg) independently
published their findings that genotype frequencies will not change in large randomly
mating populations in which mutation, migration, and selection are absent. Remember
that when genotype frequencies (and their underlying allele frequencies) don’t change, no
evolution is occurring. The Hardy-Weinberg principle, then, specifies conditions under
which evolution will
take place. It also provides a very useful tool with which to
determine whether or not evolution is taking place in a population and, if so, how
What should you know?
To fully answer this Driving Question, you should be able to
List and describe the five conditions under which a theoretical population will
be in Hardy-Weinberg equilibrium.
Explain the relationship between evolution and Hardy-Weinberg equilibrium.
Discuss whether Hardy-Weinberg conditions are likely to occur in natural
populations, and explain what that means in terms of evolution.
Given the frequency of one allele, calculate the allele and genotype
frequencies of a trait controlled by two alleles in a nonevolving population
using the Hardy-Weinberg equation.
The infographics most pertinent to the Driving Question are 14.5 and Up Close:
Calculating Hardy-Weinberg Equilibrium.
Test Your Vocabulary:
Match the following definitions to the terms they describe:
The principle that, in a nonevolving population,
both allele and genotype frequencies remain constant from one generation to the next.
List and describe the five conditions under which a theoretical population will be in
List and describe the five conditions required for a theoretical population to be in
five conditions necessary for a population to be in Hardy-Weinberg
No mutations occur: new alleles are not introduced into the