Answers to Figure Legend Questions
FIGURE 13.4 Averaging across the six groups, there are about 21 parasite species per host. This average would probably not be close to the number of parasite species found in a previously unstudied host from one of the six groups of organisms.
A reason for this is that in five of the groups (all but the trees, which had an average of 95), the average number of parasites per host is fewer than 12. Thus, we might expect that 95 parasite species would be found in another tree, 7 parasite species would be found in another wasp, etc. —but we would not expect to find 21 parasite species in a host from any of the six groups.FIGURE 13.9 The gamete-producing cells enable the parasite to disperse from a human host to a mosquito.
FIGURE 13.11 No. For example, with an infection rate of 70%, the Lake Wahapo snails are very poorly defended against parasites from their own lake, but they are reasonably well defended against parasites from both other lakes. Similarly, Lake Paringa snails are poorly defended against parasites from their own lake (infection rate = 51%), but they are well defended against parasites from Lake Mapourika (infection rate = 11%).
FIGURE 13.15 If the cycles stopped completely, we would not expect the numbers in both of the treated populations to drop in 1989 and again in 1993 —the same years that the control populations were predicted to drop based
on long-term data on population cycles in red grouse.
FIGURE 13.22 The WT and EGT+ treatments represent two types of controls. The WT treatments are unmanipulated controls; results from these controls can be compared with results from the EGT-experimental treatments. The EGT+ controls can be used to check whether the procedures used to remove (and insert) the egt gene have inadvertent effects. Hence, in the EGT+ controls, the gene is removed and then reinserted—if these experimental procedures do not have inadvertent effects, results from these controls should be similar to results from the WT controls. In fact, this is what was found.