Biology 156
Evolutionary Ecology
9 Feb 2001
Bob Podolsky
Week 5. Evolution of life-histories
Study guide
After the module on the evolution of life-histories you should be able to:
Lecture 4.2: tradeoffs involving egg size and number
1. Give a simple definition of an organism's "life-history"
2. Give examples of life-history traits, and describe how these differ from other kinds of traits
on which selection could act
3. Describe an "ideal" organism (from the perspective of fitness), and explain why trade-offs
are essential to understanding why such organisms do not exist
4. Graphically describe Lack's model for the evolution of clutch size, including assumptions
made by the model and a description of why such assumptions were made
5. Describe features of the study that Boyce and Perrins used to test one assumption and one
prediction of Lack's model
6. From the data presented in class, explain whether B&P's data supported the assumption that
survivorship would decline as a function of clutch size
7. Provide an explanation for your answer to #6, and by doing so point out an implicit
assumption of Lack's model not mentioned previously
8. From the data presented in class, explain whether B&P's data supported the prediction that
birds would on average produce clutches that maximized the number of surviving offspring
9. Give two alternative hypotheses to explain your answer to #8
10. Given data presented in class, explain why the parasitoid wasps studied by Charnov and
Skinner would be selected to adjust the number of eggs laid depending on the species of host
11. Give a graphical/mathematical argument for what conditions would lead a parasitoid wasp to
lay fewer eggs than the "Lack clutch" size in a given host
12. Graphically describe the Smith-Fretwell model for the evolution of offspring size, including
assumptions made and a description of why these assumptions are justified
13. Explain the fitness costs of high between-generation variance in reproductive success
14. Explain two methods that Sinervo used to manipulate offspring size in populations of lizards
15. Explain the reasons why Sinervo made these manipulations, and two reasons why such
methods are more informative than relying simply on natural variation in offspring size
16. Describe differences in results between years of his study, including the potential for conflict
between the evolutionary interests of the mother and of her individual offspring
17. Explain the predictions that Fox et al. made regarding the size of eggs that beetles would lay
on different seeds
18. Explain how Fox et al. demonstrated that egg size was an adaptive response to seed quality
Lecture 5.1-2. The evolution of life-history traits and senescence
19. Define senescence, and describe Bell's observations of mortality rates in 6 asexual freshwater
species
20. Explain the function of a life table, recognizing its components, the life-history traits that it
includes, and two measures that can be used to summarize a genotypes fitness
21. Give examples of tradeoffs between life history traits that can be illustrated in a life table
22. Making reference to a hypothetical life table, describe two general evolutionary benefits of
early reproduction
23. Despite the benefits you listed in 22, explain circumstances that may favor delayed maturity
and reproduction
24. Explain work that Reznick et al. did in both the field and laboratory to demonstrate that sizerelated predation can have an effect on life-history evolution
25. Describe typical measurements that have been used to identify senescence in populations,
both in terms of life-history traits and measures of performance
26. Distinguish between two hypotheses for processes that could underlie patterns of senescence,
including their testable assumptions
27. Describe an important assumption of physiological hypotheses for the evolution of
senescence, and explain why the hypothesis predicts that lifespan and metabolic rate should
be functionally related
28. Explain how Luckinbill et al.'s data were used to test an assumption of the physiological
hypothesis for the evolution of senescence
29. Explain how the degree of ecological mortality can affect the costs and benefits of putting
energy into growth, maintenance, and reproduction
30. Describe Austad's study and explain what his comparisons demonstrated about the evolution
of senescence in opossum populations
31. Name and distinguish between two hypotheses for mechanisms that could underlie
evolutionary processes responsible for senescence, including their assumptions about the
nature of mutations that would underlie senescence
32. Explain whether and why Rose's results supported one or the other of these hypotheses