Answers to Figure Legend Questions

FIGURE 7.2 Starting with the fish on the top left and proceeding clockwise, the genders are male, smallest nonbreeder, female, and largest nonbreeder. We can be confident of these predictions because the largest fish is female, the next largest a male, and the rest are sexually immature nonbreeders.

FIGURE 7.4 A 5-m-tall tree growing in a cool, moist climate is estimated to have a trunk diameter between 10 and 20 cm (the log scale makes it difficult to provide a precise estimate, but it is probably close to 15 cm), while a 5-m- tall tree growing in a desert climate is estimated to have a trunk diameter between 20 and 30 cm (probably close to 22 cm). To illustrate how these estimates are obtained: if you follow the line that moves horizontally to the right from the 5-m mark on the y axis, that line intersects the blue curve (the regression line for a cool, moist climate) at a point whose trunk diameter is about 15 cm.

FIGURE 7.7 The larva would be genetically identical to the polyp because both result from the same zygote (which in turn was produced when a sperm cell fertilized an egg cell). Two different larvae, however, would not be genetically identical because each resulted from a different fertilization event.

FIGURE 7.9 In generation 3 there are 8 sexual and 16 asexual individuals, while in generation 4 there will be 16 sexual and 64 asexual individuals.

Note that the number of sexual individuals is increasing half as rapidly as the number of asexual individuals. This occurs because half of the offspring produced by sexual females are males (and males do not give birth to offspring). As a result, from one generation to the next, the number of sexual individuals doubles whereas the number of asexual individuals quadruples.

FIGURE 7.10 The blue line shows the results for the control populations. In this study, the experimental populations were exposed to a bacterial pathogen while the control populations were not. The results show that the outcrossing rate remained roughly constant in the control populations whereas it increased dramatically in the experimental populations, indicating that increased levels of outcrossing are favored by selection in populations exposed to pathogens.

FIGURE 7.15 For males with a thorax length of 0.8 mm, those kept with virgin females had an average life span of about 40 days while those kept with previously mated females had an average life span of about 63 days.

FIGURE 7.23 No. When c > 1, the average age of sexual maturity is greater than the average life span. For this to occur, the majority of individuals must die before they are old enough to reproduce.