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Chapter 17
The Evolution of Populations and Species
CHAPTER OUTLINE
Genetic variation in a population
The Hardy-Weinberg principle
Microevolution
Mutation increases variation in the gene pool
Genetic drift causes changes in allele frequencies through random events
The founder effect occurs when a few individuals establish a new colony
The migration of pollen or seeds causes gene flow in plants
Plants and the Environment: Extinction Today—Endangered and Threatened Species
CHAPTER OBJECTIVES
1. Distinguish between the gene pool of a population and the genotype of an individual.
2. Discuss the significance of the Hardy-Weinberg principle as it relates to evolution.
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LECTURE OUTLINE
I. Some definitions
A. What is the difference between a population and a species?
B. What does “microevolution” mean?
C. What is a gene pool (allele pool might be a better term)?
II. The Hardy-Weinberg law: A yardstick by which to measure evolution.
B. What is genetic drift?
1. What condition is present in a population subject to drift?
2. How does drift affect variability in a population?
3. On what basis is an allele eliminated?
C. What is gene flow?
1. How does it affect variation within a population?
3. How does natural selection function to change allele frequencies?
IV. What is the biological species concept, and what are some problems associated with it?
A. Why is reproductive isolation important in the concept of a species?
1. What isolating mechanisms operate to prevent pollination and fertilization?
a. Differences in flowering time.
b. Different structures for different pollinators.
2. What mechanisms operate postfertilization?
a. Failure of embryonic or juvenile development.
b. How common is polyploidy in plants compared to animals?
c. What is allopolyploidy, and how is reproductive isolation achieved?
V. What is “adaptive radiation” and when is it most likely to occur?
VI. What is extinction?
KEY TERMS
adaptation, p. 332
adaptive radiation, p. 341
gene flow, p. 334
gene pool, p. 330
natural selection, p. 334
population, p. 328
TEACHING TIPS
1. Ask students to consider the question, “Why does natural selection favor the
development of prefertilization isolating mechanisms?” The reason is in the extreme
2. With a little research, you can prepare a time line that follows the geological and
biological history of your part of the continent. Many areas have remnant populations
3. It is difficult to avoid using the names of geological periods and eras. It helps
students to know that the geologic timescale was developed based on changes in
4. Bring in examples of polyploid plants, such as daylily, tobacco, chrysanthemum,