Terms to know:  temporal variation, coadapted gene complex, correlated character, adaptive landscape, negative frequency dependent selection, positive frequency dependent selection, linkage disequilibrium

Questions:

1. Explain what each of the following is, and then explain why they complicate our ability to model natural selection using the "simple" mathematical model of natural selection we have used in class:  (a) temporal variation in the environment (b) frequency dependent selection (c) coadapted gene complexes (d) correlated characters (e) the existence of quantitative traits (f) linkage disequilibrium
2. What are three causes of linkage disequilibrium?  Why is understanding linkage disequilibrium important if we are to understand the evolution of traits?
3. Compare and contrast negative frequency dependent selection and selection in a changing environment.  Which do you think is more likely to maintain genetic variation over a long period of time? Why?
4. What aspects of disease organisms make them likely to cause  frequency dependent selection in their hosts?  Do they cause positive or negative frequency dependent selection?
5. Give examples of situations in which you would expect to see negative frequency dependent selection and examples of situations in which you would expect to see positive frequency dependent selection.  What is the effect of each kind of frequency dependent selection on the expected amount of genetic variation in a characteristic?
6. What is meant by correlated characters?  Use this concept to explain how a trait that in itself does not affect survival or reproduction of an organism could show directional change in trait value over evolutionary time.
7. In a species of salamander you find that individuals vary in both the size of their toes and in how much webbing there is between the toes.  You discover that the two characters are correlated in that the more webbing there is between toes the shorter the toes are.  Suppose that the environment of these salamanders becomes more aquatic and that individuals with webbing between the toes can swim better and therefore survive better in an aquatic environment.  Toe length has no direct effect on survival or reproduction.  How would you expect the amount of toe webbing to change in the population over time?  How would you expect toe length to change in the population over time?  Explain why.
8. How have Darwin's Finches been used to study evolution of correlated characters?  Which characters in Darwin's Finches are directly subject to selection (because they result in differences in survival / reproduction)?  Which characters have evolved as correlated characters?
9. Explain how the concept of coadapted gene complexes is related to the concept of an adaptive landscape.
10. In an adaptive landscape, will populations always evolve to have the traits that confer the highest fitness?  Why or why not?
11. What is meant by an adaptive landscape?  What do the peaks and valleys in an adaptive landscape represent?
12. Suppose you find that in a snake species, the fitness of the following three traits depend on each other:  length of fangs, presence of venom, and coloration.  Snakes with venom, long fangs, and bright coloration have high fitness, but snakes with venom, long fangs, and dull coloration have lower fitness since they are not recognized as toxic and are frequently attacked by potential predators.  Snakes with venom and short fangs also have lower fitness, regardless of their coloration, because they cannot effectively deliver their venom with the short fangs so that producing venom is a waste of energy.  Snakes with short fangs, no venom, and dull coloration have higher fitness than those with short fangs and venom because they are not wasting energy producing venom.  What concepts are being illustrated here?
13. Distinguish between coadapted gene complexes and correlated characters.
14. Try to think of your own examples (not from lecture, reading, etc.) of traits that would be likely to occur in coadapted gene complexes.  Try to think of examples of traits that would probably be correlated characters.