Food chains are sometimes short becausea. only a single species of herbivore feeds on each plant species.b. local extinction of a species causes extinction of the other species in its food chain.c. most of the energy in a trophic level is lost as energy passes to the next higher level.d. most producers are inedible.

Pioneer species tend to have high and lower survivorship.

According to the generalized species-area curve, when habitat is reduced to 50% of its original size, approximately of the species once present there will be lost.a. 10%;b. 25%;c. 50%;d. 90%;e. it is impossible to estimate the percentage

Predators that are keystone species can maintain species diversity in a community if theya. competitively exclude other predators.b. prey on the community's dominant species.c. reduce the number of disruptions in the community.d. prey only on the least abundant species in the community.

Which of the following organisms is mismatched with its trophic level?a. algae—producerb. phytoplankton—primary consumerc. carnivorous fish larvae—secondary consumerd. eagle—tertiary or quaternary consumer

Which of the following best illustrates ecological succession?a. A mouse eats seeds, and an owl eats the mouse.b. Decomposition in soil releases nitrogen that plants can use.c. Grasses grow in a deserted field, followed by shrubs and then trees.d. Imported pheasants increase in numbers, while local quail disappear.

Which of the following could qualify as a top-down control on a grassland community?a. limitation of plant biomass by rainfall amountb. influence of temperature on competition among plantsc. influence of soil nutrients on the abundance of grasses versus wildflowersd. effect of grazing intensity by bison on plant species diversity

What is a disturbance? Consider the role of fire in a forest. Compare the consequences of high-frequency versus low-frequency fire, and high severity versus low severity of fire.

The most plausible hypothesis to explain why species richness is higher in tropical than in temperate regions is thata. tropical communities are younger.b. tropical regions generally have more available water and higher levels of solar radiation.c. higher temperatures cause more rapid speciation.d. diversity increases as evapotranspiration decreases.