Biology 100/101
Lecture 23:
Microevolution: Allele Frequencies

Text Readings
in Lewis		 Review questions
Chapter 18
Chapter 20		 Pg. 388: To Review;
1, 2, 3, 5, 6, 7, 9, and 10
To Think About; 4 and 7
Pg. 420-1: To Review;
1, 3, 5, 6, and 7
To Think About; 3, 6 and 7

For feedback, post questions and ideas in the folder "Text 'Review' and 'To Think About' Questions" in the Biology Chat Section of Web Crossing.

Objectives
 After studying this material you should be able to:

  1. describe evolution in terms of change in allele frequency in a population.

  2. list and explain the factors that must be in play for a population to exprience NO change in allele frequencies over several generations (Hardy-Weinberg equilibrium).

  3. list and explain factors that increase genetic variation in a population.

  4. list and explain factors that decrease genetic variation in a population.

  5. describe the conditions necessary for two populations of one type of organism to evolve into two separate species.

Key Terms:
Understand the relationships among these terms:

Terms from lecture #22
biological evolutionselectionnatural selection
microevolutionmutationallele frequencies
directional selectionstabilizing selectiondisruptive selection
genetic variationscientific theoryscientific fact
differential reproductionsexual selection"fitness"
macroevolutionbalanced polymorphism

New Terms
genetic driftHardy-Weinberg
equilibrium		bottle neck
founder effectgene flow adding alleles
removing alleles chance events species
speciation reproductive isolation random mating
sexual reproduction

Web Resources for Evolution

  • The Talk.Origins Archive - a compilation of information and conversations about evolution. Includes a search option.

  • Biology and Evolutionary Theory This is a menu page from Talk.Origins with links to essays about evolution including some of those below and others you might find interesting.

  • Introduction to Evolutionary Biology Version 2 (from Talk.Origins)
    This is rather lengthy, but scan through it to help with the terms in the table above.

  • What is Evolution?

  • Evolution is a Fact and a Theory

  • The basics of sexual selection

  • Sexual selection 2

  • Discovery Chanel Online: Beyound Darwin, by Bill Belleville

  • Creationism - (with an obvious Evolutionist spin from Talk.Origins)

  • Charles Darwin Research Station Galapagos Islands

  • Other Links from Talk.Origins
    This includes links to creationist pages as well as others.

    Web Crossing Resources

    Extra Credit Discussion - Book Reviews of The Beak of the Finch
    Some of your classmates are reading, reviewing, and discussing this book dealing with natural selection and evolution.

    Backyard Evolution: The Case of the Escaped Escargots

    Genetic Variation in a Population

    Speciation, Genetic Drift, Gene Flow, and Reproductive Isolation:
    Or what does it take to get a new snail?