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The Evolution of Populations Resources


People did not understand the mechanisms of inheritance, or genetics, at the time Charles Darwin and Alfred Russel Wallace were developing their idea of natural selection. Scholars rediscovered Mendel’s work in the early twentieth century, and over the next few decades scientists integrated genetics and evolution in what became known as the modern synthesis—the coherent understanding of the relationship between natural selection and genetics that took shape by the 1940s. Natural selection can affect a population’s genetic makeup, and, in turn, this can result in the gradual evolution of populations. In the early twentieth century, biologists in the area of population genetics began to study how selective forces change a population through changes in allele and genotypic frequencies.  Adaptive evolution is the process by which natural selection increases the frequency of beneficial alleles in the population, while decreasing the frequency of deleterious alleles.

Learning Objectives

  • Define population genetics and describe how scientists use population genetics in studying population evolution

  • Define the Hardy-Weinberg principle and discuss its importance

  • Use Hardy-Weinberg Equilibrium to solve population genetics problems

  • Describe the different types of variation in a population.

  • Explain why only natural selection can act upon heritable variation.

  • Explain how each evolutionary force can influence a population's allele frequencies.

  • Describe the founder effect and the bottleneck effect.

  • Explain the different ways natural selection can shape populations.

  • Explain the difference between natural selection and sexual selection.

  • Explain why evolution does not produce perfect organism

Recommended Textbook Resources

Chapter 19: The Evolution of Populations Biology 2e

OpenStax: Biology 2e

This chapter discusses how populations change over time.  It includes a brief introduction to Hardy-Weinberg Equilibrium, a discussion of the evolutionary forces that cause population to change, and a review of the different mechanisms of adaptive evolution. 

Student Assessment Activities

Student Assessment Activities are below; instructors can also Download the Evolution of Populations Student Activities Word File or View the Evolution of Populations Student Activity Google Doc.

Project 1:

Instructors should print the student handout for the Allele and Phenotype Frequencies in Rock Pocket Mouse Populations Lab from and distribute to the students.  Before students begin the lab, show the video entitled “Natural Selection and the Rock Pocket Mouse” found at 

Students then complete Parts 1 and 2 of the lab.  

Optional: If students have access to Microsoft Excel, they can complete Part 3. The Excel spreadsheet can be downloaded at  The Excel spreadsheet should be downloaded by the instructor and then electronically distributed to the students.  In addition to the lab handout and spreadsheet, this web link contains the teacher’s manual for the lab, so students should not access the activity online on their own

Project 2:

Find the correct answers to the end of the chapter “Review Questions.” Note the page number on which you found the answer. Be prepared to share and explain your answers in a group setting. 

Project 3:

Answer the end of the chapter “Critical Thinking Questions.” Note the page number on which you found the answer. Be prepared to share and explain your answers in a group setting.