Module 8 Population Genetics

4.8.3 page 4

Reflect and Connect

In this lesson you have learned how to calculate changing frequencies of alleles. These changes can illustrate that a population is evolving. These changes can be in response to a changing environment. For example, the increase in the allele for light brown hair in many species of gopher is increasing as these individuals survive in a habitat that is becoming increasingly arid.

Why do ecologists study population changes? By using past studies what can they predict. Scientists are learning about the affects of climatic changes on species and their characteristics. They can use these studies to explain changes in populations due to weather conditions, disease, change in prey-predator relationships, and many other factors that you have read about in your text. Humans are realizing the effect of our practices on the environment and the impact to other species and their populations. By understanding the causes of allele frequency changes, we may better understand the impact that man has on the ecosystem.

Lesson Summary

• The Hardy Weinberg equation is a tool used to determine if genetic change (evolution) is actually occurring in a population.
   
• In terms of the allele frequencies, p represents the frequency (#/total) of the dominant allele in the gene pool. q represents the frequency of the recessive allele in the gene pool. p + q = 1 because the dominant alleles plus the recessive alleles make up the whole gene pool.
• p2 represents the frequency of the homozygous dominant genotype in the population = f(AA)
• 2pq represents the frequency of the heterozygous genotype = f(Aa)
• q2 represents the frequency of the homozygous recessive genotype = f(aa)
• p2 + 2pq + q2 = 1 because f(AA) + f(Aa) + f(aa) = all individuals of the population.