Look again at Figure, which illustrates fertility and survival as a function of age in thr...

Look again at Figure, which illustrates fertility and survival as a function of age in three different species.

Figure Aging in three animals (a) For female collared flycatchers, the number of young fledged each year declines after age 3 (p < 0.001).The probability of survival from year to year declines slightly, but not significantly, after age 2. Sample sizes in parentheses. From Gustafsson and Pärt (1990). (b) For malered deer, the number of calves fathered each year declines after age 9; for females, the number of calves produced declines after age 13. For both sexes, the probability of surviving from year to year plummets after age 9. FromClutton-Brock et al. (1988). (c) For female fruit flies (Drosophila melanogaster), the average number of eggs laid per day declines after 12 days. In three lab populations, the probability of surviving from day to day falls at about 20 days. Modified from Rose (1984).

a. What similarities are there across all three species? What is the general trend in fertility and in annual

probability of survival? Why are these trends considered to be an evolutionary puzzle?

b. Which species has the best probability of survival even in old age? This is a characteristic of this taxon. Do you remember another animal (a mammal, discussed later in this chapter) that has a similarly high probability of survival in old age? What trait do these long-lived animals have in common?

c. In red deer, how do patterns of survival and reproduction vary with the two sexes? Why do you think these differences occur between males and females?