Chapter 36

After seeds have sprouted, gardeners often pull up some of the seedlings so that only a few grow to maturity. How does this practice help produce the best yield? a. by increasing \(K\) b. by decreasing \(r\) c. by reducing intraspecific competition d. by adding a density-independent factor to the environment

To figure out the human population density of your community, you would need to know the number of people living there and a. the land area in which they live. b. the birth rate of the population. c. the dispersion pattern of the population. d. the carrying capacity.

The term \((K-N) / K\) a. is the carrying capacity for a population. b. is greatest when \(K\) is very large. c. is zero when population size equals carrying capacity. d. increases in value as \(N\) approaches \(K\).

With regard to its rate of growth, a population that is growing logistically a. grows fastest when density is lowest. b. has a high intrinsic rate of increase. c. grows fastest at an intermediate population density. d. grows fastest as it approaches carrying capacity.

Which of the following represents a demographic transition? a. A population switches from exponential to logistic growth. b. A population reaches a fertility rate of zero. c. There are equal numbers of individuals in all age-groups. d. A population switches from high birth and death rates to low birth and death rates.

Skyrocketing growth of the human population appears to be mainly a result of a. a drop in death rate due to sanitation and health care. b. better nutrition boosting the birth rate. c. the concentration of humans in cities. d. social changes that make it desirable to have more children.

The mountain gorilla, spotted owl, giant panda, snow leopard, and grizzly bear are all endangered by human encroachment on their environments. Another thing these animals have in common is their \(K\) -selected life history traits. Why might they be more easily endangered than animals with \(r\) -selected life history traits? What general type of survivorship curve would you expect these species to exhibit? Explain your answer.

Another hypothesis for snowshoe hare population cycles proposes that they are caused by sunspot activity. According to this hypothesis, sunspot activity affects the chemicals present in the plants eaten by hares, which in turn affects the quality of the food. What testable predictions are generated by this hypothesis?

Many people regard the rapid population growth of developing countries as our most serious environmental problem. Others think that the growth of developed countries, though slower, is actually a greater threat to the environment. What kinds of environmental problems result from population growth in (a) developing countries and (b) developed countries? Which do you think is the greater threat? Why?