Chapter 53

According to optimal foraging theory, predators: a. always feed on the largest prey possible. b. always feed on the prey that are easiest to catch. c. choose prey based on the costs of capturing and consuming it compared to the energy it provides. d. feed on plants when animal prey are scarce. e. have coevolved mechanisms to overcome prey defenses.

The use of the same limiting resource by two species is called: a. brood parasitism. b. interference competition. c. exploitative competition. d. mutualism. e. optimal foraging

The range of resources that a population can possibly use is called: a. its fundamental niche. b. its realized niche. c. character displacement. d. resource partitioning. e. its relative abundance.

Differences in the bill sizes of finch species living on the same island in the Galápagos may be caused by: a. predation. b. character displacement. c. mimicry. d. interference competition. e. cryptic coloration.

A keystone species: a. is usually a primary producer. b. has a critically important role in determining the species composition of its community. c. is always a predator. d. usually reduces the species diversity in a community. e. usually exhibits aposematic coloration.

Species richness is often highest in communities where disturbances are: a. very frequent and severe. b. very frequent and of moderate intensity. c. very rare and severe. d. of intermediate frequency and moderate intensity. e. very rare and mild.

The change in the species composition of a terrestrial community from bare and lifeless rock to climax vegetation is called: a. disturbance. b. competition. c. secondary succession. d. primary succession. e. facilitation.

Bacteria that live in the human intestine assist digestion and feed on nutrients the human consumed. This relationship might best be described as: a. commensalism. b. mutualism. c. endoparasitism. d. ectoparasitism. e. predation

The equilibrium theory of island biogeography predicts that the number of species found on an island: a. increases steadily until it equals the number in the mainland species pool. b. is greater on large islands than on small ones. c. is smaller on islands near the mainland than on distant islands. d. can never reach an equilibrium number. e. is greater for islands near the equator than for islands near the poles

Five processes can foster microevolutionary change: gene flow, genetic drift, mutation, natural selection, and nonrandom mating (see Section 21.3 ). Which of those processes might contribute to the evolution of Batesian mimicry in two butterfly species? Would the same processes affect both the mimic and the model similarly? Which processes might have contributed to the evolution of the mutualistic relationship between ants and acacia trees, and how would their action on the two mutualists differ?

The table below shows how many individuals were recorded for each of five species in five separate communities (a-e). Which community has the highest species diversity? $$ \begin{array}{|cccccc|} \hline & & & & & & \\ & & \text { Species } & \text { Species } & \text { Species } & \text { Species } & \text { Species } \\ \text { Community } & 1 & 2 & 3 & 4 & 5 \\ \hline a & 90 & 10 & 0 & 0 & 0 \\ \hline b & 80 & 10 & 10 & 0 & 0 \\ \hline c & 25 & 25 & 25 & 25 & 0 \\ \hline d & 2 & 4 & 6 & 8 & 80 \\ \hline e & 20 & 20 & 20 & 20 & 20 \\ \hline \end{array} $$

After reading about the two potential biases in the scientific literature on competition, describe how future studies of competition might avoid such biases.

How do human activities disrupt the process of succession in terrestrial communities? Would you describe most of our activities as mild disturbances, moderate disturbances, or severe disturbances?

Humans are destroying natural communities at an ever-increasing pace. Using the predictions of the theory of island biogeography, develop hypotheses about what might happen as patches of natural habitats get smaller and smaller. How would you test these hypotheses?

Chaparral, a community of woody shrubs that is fairly common in California, often grows adjacent to grassland. The two communities are consistently separated by a "bare zone," usually less than 1 m wide, where no vegetation of either type grows. Ecologists have proposed two possible explanations for this strip of bare soil: (1) that the leaves of chaparral shrubs release harmful, water-soluble chemicals that keep the grass seeds from germinating in the adjacent soil; and ( 2 ) that small mammals living in the dense cover provided by chaparral consume the grass seeds before they germinate; the animals do not venture very far from the shrubs because they would be easy targets for predatory hawks. Design a set of field experiments to test the two hypotheses.