Answers to Figure Legend Questions

FIGURE 11.11 Since there were about 35 breeding females in 1975, results from previous years suggest that roughly 4 young per female should have been reared to independence. In fact, fewer than 1.5 young per female were reared to independence, suggesting that conditions on the island were different in 1975 than in other years (there could have been a drought or a disease outbreak, among many other possibilities).

FIGURE 11.12 High-density populations are increasing in density in (A) because λ is greater than 1 in those populations. In contrast, in (B) the high- density populations are decreasing in size because r is less than zero in those populations.

FIGURE 11.14 As N becomes close to K, the term (1 - N/K) becomes increasingly close to zero; this causes the population growth rate, dN/dt, to become close to zero. A population with a growth rate of zero does not increase in size; hence, as N approaches K, the population stops increasing in size.

FIGURE 11.17 100 sheep survive to age 11; thus, 10% (100/1,000) of sheep survive from birth to age 11.

FIGURE 11.18 About 47% of Gambians born in the hungry season live to age 45; a similar percentage (48.5%) of U.S. females live to be 85 years old.

FIGURE 11.20 The graph shows that the human population is projected to have an annual growth rate of 0.5% in 2050. This rate is greater than zero, so the human population will still be increasing in size in 2050.

FIGURE 11.21 The best-estimate curve indicates there will be 9.6 billion people in 2050, and Figure 11.20 indicates that our annual growth rate will be 0.5% at that time. Hence, from 2050 to 2051, we would expect to add about 48 million (9,600,000,000 ? 0.005) to our population. Thus, the human population size in 2051 would be about 9,048,000,000.