Biology 156
Evolutionary Ecology
31 Jan 2001
Bob Podolsky
Weeks 3-4. Evolutionary ecology of sexual reproduction
Study guide
After the module on the evolution of sex you should be able to:
Lecture 3.1
1) Define the major differences between sexual and asexual reproduction
2) Explain why asexual reproduction and self-fertilization have different evolutionary
consequences
3) Describe the general pattern of how asexual and sexual reproduction are distributed among
major groups within the animal kingdom
4) Explain why, for humans, the prevalence of sexual reproduction is not necessarily evidence
that sexual reproduction is a more adaptive mode than asexual reproduction
5) Give a brief mathematical argument for why, all else being equal, a single mutant that
reproduces asexually should quickly take over a population of sexuals
6) Give a sense of the time scale over which this process would happen for different population
sizes of sexuals
7) Describe why the output of Maynard Smith’s model presents a paradox for evolutionary
biology, and explain how falsifying each assumption would help to explain the paradox
8) Explain how, in their experiments, Dunbrack et al. simulated asexual reproduction while
using a species that only reproduces sexually
9) Explain the reasoning of Dunbrack et al. in giving asexual populations a three-fold advantage
in reproduction
10) Design an experiment that could test Maynard Smith’s first assumption concerned with
differences in fecundity between the two modes of reproduction
Lecture 3.2
11) Describe the major distinction between ecological and genetic hypotheses for the
maintenance of sexual reproduction
12) Name and distinguish among three different hypotheses for the ecological benefits of sexual
reproduction
13) Describe the methodology used by Lively in his research
14) Describe what assumptions Lively made about lakes and streams in trying to distinguish
between two hypotheses for the maintenance of sex
15) Describe the predictions Lively made from these assumptions, and whether his data
supported either of these two hypotheses
16) Explain the evidence that Lively used to conclude that the "Red Queen" model was the best
supported of the three hypotheses
17) Explain why Lively's correlation between infection rate and male frequency could have been
an artifact of the correlation of these variables with population density
18) Explain the calculation of why each human gamete is likely to carry on average one mutation
in a functional gene, and explain why this probability is significant to genetic hypotheses for
the mainenance of sex
19) Briefly explain the basis of "Muller's ratchet", and why sexual but not asexual reproduction
can eliminate the effect
20) Explain why the elimination of deleterious mutations may be more important than the
accumulation of beneficial ones as an evolutionary explanation for the maintenance of sex
21) Explain how Muller's argument differs from one based on the accumulation of beneficial
mutations
22) Design an experiment to test the hypothesis that sex is important for increasing the union of
synergistically beneficial mutations
Lecture 4.1
23) Explain the distinction between sex and sexes, and which kinds of organisms tend to show
the former but not the latter
24) Explain what is meant by the terms isogamy and anisogamy
25) Describe in words and graphs the two basic assumptions that Parker et al. used in their
argument for the evolution of anisogamy, and why these assumptions suggest that different
selection pressures may be acting on different members of a population
26) Give the relative sizes of a typical egg and a typical sperm in a free-spawning marine
invertebrate, and explain why the two general sizes could both be favored by selection
27) Explain why dissortative mating is likely to evolve once anisogamy has evolved
28) Explain the rationale behind the hypotheses tested by Knowlton and by Madsen and Waller
in their studies of protists, and the conclusions they drew from their data
29) Give a potential problem with these data that could weaken support for their conclusions
30) Explain one challenge to Parker et al.'s model based on their assumption concerning the
relationship between zygote size and survival
31) In mathematical terms, give a brief argument for the likelihood that a genotype producing
macrogametes can become established in a population of microgamete producers
32) Describe the main challenge posed by Levitan to the traditional model for the evolution of
anisogamy