Chapter 20 Outline

Process of Evolution

The gene pool concept and the Hardy-Weinberg law serve as background to considering the agents of evolutionary change, including adaptation by natural selection. Allopatric and sympatric speciation are also included in this chapter.

Chapter Outline

In this chapter outline, the learning objectives and the selected key terms are given for each major head in the chapter.

What Causes Variations? (p. 312)

1. State the sources of variation in a population of sexually reproducing diploid

organisms.

Selected Key Terms: population

How to Detect Evolution (p. 314)

2. Explain the Hardy-Weinberg law, along with its conditions.

gene pool, Hardy-Weinberg law

What Causes Evolution? (p. 315)

3. List and discuss the agents of evolutionary change.

4. Contrast the effects of gene flow and genetic drift on the gene pool of a

population.

gene flow, genetic drift

Adaptation Occurs Naturally (p. 318)

5. State the steps required for adaptation by natural selection in modern terms.

6. Distinguish among directional, stabilizing, and disruptive selection by giving

examples.

7. Tell how variation is maintained in a population.

fitness, directional selection, stabilizing selection, disruptive selection

Considering Speciation (p. 322)

8. Explain the biological definition of a species.

9. Discuss the importance of reproductive isolating mechanisms, and give examples of

both premating and postmating isolating mechanisms.

10. Explain and contrast allopatric and sympatric speciation.

speciation, species, premating isolating mechanism, postmating isolating mechanism,

allopatric speciation, sympatric speciation, adaptive radiation

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