Zoology 10th Edition by Stephen Miller,John Harley

تمرين 1

Consider the age pyramid shown in figure 6.13. Next, think about the discussion of human population growth on page 108. What would the age pyramids of high-fertility, intermediate-fertility, and low-fertility countries look like? What age-structure problems will need to be overcome in societies with low fertility rates?
FIGURE 6.13 Human Age Pyramids from 2010. ( a ) In developed countries, the age structure is parallel-sided because mortality in all age classes is relatively low. In this example, the slight widening of the pyramid in the 45 to 65 age range is because of the "baby boom" that occurred between 1945 and 1965. ( b ) In developing countries, a greater proportion of the population is in the prereproductive age classes. High mortality compensates for high birthrates, and the pyramid is triangular. As technologies reduce infant mortality and prolong the life span of the elderly, populations increase rapidly.