vocabulary:  Hardy-Weinberg Principal, mutation, migration, genetic drift, natural selection, sexual selection
 

1. Randomization in experimental design
   
   1. used when a variable cannot be controlled for
      1. example: genotype in sexually-reproducing organisms
   2. evenly distributes variation among treatment groups
2. Evolutionary change = change in phenotype due to underlying change in allele frequencies
1. detecting evolutionary change: the null model
1. definition of "null model"
2. Hardy-Weinberg principle: constant allelic frequencies in the absence of evolution
3. Natural selection is only one possible source of evolutionary change
1. we will only discuss genetic drift and sexual selection in class;  students from 1B should review the entire chapter.
2. genetic drift: sampling error in action
1. class exercise in sampling. Everyone should bring a coin.
2. sampling error is random with respect to phenotype
3. bottlenecks:  a special case
4. inbreeding
   
3. Natural selection
1. the only evolutionary process that is non-random
2. "flavors"
1. directional, stabilizing, disruptive
3. sexual selection: a special case

1.  Why is it important for the Hardy-Weinberg Principle to hold, that all individuals in the population contribute to the "gene pool" and that all pairings of gametes (matings) occur randomly?

2.  Which processes of evolution discussed in lecture and in the text book are random, and which are non-random?

 
1. mutation
2. drift
3. inbreeding
4. migration
5. natural selection
6. sexual selection

1. mutation
2. drift
3. inbreeding
4. migration
5. natural selection
6. sexual selection

5. Will an expanded diet lead to evolution of food choice under the following circumstances? Why or why not?

A farmer plows up a piece of prairie and plants potatoes (a plant in the family Solinacae from South America). In the prairie, there is a plant in the family Solinacae that is the primary food source of a beetle. Some females in the prairie population encounter the potato field, and some of them lay their eggs on the potato plants. The propensity to accept the new plant is genetically determined. Larvae on the potatoes actually grow faster than on the native plant because the potatoes have fewer chemical defenses against herbivory (humans have selected for low phytochemical content in their crop plants). Thus the potato-fed larvae mature earlier, and the beetles in the potato field have more generations during the summer.
 

6. Under which of the following scenarios could new mating signals evolve through sexual selection? For each, explain why or why not evolution by sexual selection will not occur. Note: evolution by sexual selection requires the same three components as evolution by natural selection.

(A) Females in a population of moths vary in the ratio of different chemicals found in their pheromone signal. Daughters produce the same mixture of chemicals as their mothers regardless of the environmental conditions. Most males in the population prefer one particular chemical ratio of pheromones; females producing different combinations are less likely to mate. Sons tend to prefer the chemical ratio most similar to that of their mother.

(B) Males crickets respond to temperature: at warmer temperatures, the trill production is more frequent. Females must be at the same temperature in order to recognize the song of the males of their species.

7.  In crickets, females of a given species recognize potential mates primarily by the frequency of the chirps (number of chirps/second).  Wasps that parasitize a particular species of cricket also recognize potential hosts by the frequency of the chirps.  Can this be considered an example of convergent evolution of sound perception (hearing) in these two groups?

8.  If different environmental factors vary in their importance over time, and they favor different phenotypes, such as in the presentation of body size in swifts (pg. 440-441), will directional selection necessarily reduce phenotypic variation within a population?

9.  How might medical advances in neonatal care alter the stabilizing selection for infant weight at birth (pg. 441, figure 22.8)?

10.  Imagine that a mutation occurs in a gene that codes both for a male's ability to detect a female's scent, and the chemical composition of the scent produced by the female. Heterozygous females produce two chemical compounds, heterozygous males can detect both.  The mutation happens in a male, making the male heterozygous at that gene.  He mates with a homozygous female.  What proportion of his offspring will be sensitive to (if male) or capable of producing (if female) both compounds?
 (A) none  (B) 1/4  (C) 1/2  (D) 3/4  (E) all
 

Answers