The symbols +, -, and o are to be used to show the results of interactions between individuals and groups of individuals in the examples that follow. The symbol + denotes a positive interaction, - denotes a negative interaction, and o denotes where individuals are not affected by interacting. The first symbol refers to the first organism mentioned.

What interactions exist between cellulose-digesting organisms in the gut of a termite and the termite?

+/+

The symbols +, -, and o are to be used to show the results of interactions between individuals and groups of individuals in the examples that follow. The symbol + denotes a positive interaction, - denotes a negative interaction, and o denotes where individuals are not affected by interacting. The first symbol refers to the first organism mentioned.

What interactions exist between mycorrhizae and evergreen tree roots?

+/+

Which of the following statements is consistent with the principle of competitive exclusion?

Even a slight reproductive advantage will eventually lead to the elimination of the less well adapted of two competing species.

According to the competitive exclusion principle, two species cannot continue to occupy the same

niche

Which of the following best describes resource partitioning?

slight variations in a species niche that allow similar species to coexist

As you study two closely related predatory insect species, the two-spot and the three-spot avenger beetles, you notice that each species seeks prey at dawn in areas without the other species. However, where their ranges overlap, the two-spot avenger beetle hunts at night and the three-spot hunts in the morning. When you bring them into the laboratory and isolate the two different species, you discover that the offspring of both species are found to be nocturnal. You have discovered an example of

resource partitioning.

Resource partitioning would be most likely to occur between

sympatric populations of species with similar ecological niches.

Which of the following is an example of cryptic coloration?

a "walking stick" insect that resembles a twig

Which of the following is an example of Müllerian mimicry?

two species of unpalatable butterfly that have the same color pattern

Which of the following is an example of Batesian mimicry?

a nonvenomous snake that looks like a venomous snake

Which of the following is an example of aposematic coloration?

the brightly colored patterns of poison dart frogs

Dwarf mistletoes are flowering plants that grow on certain forest trees. They obtain nutrients and water from the vascular tissues of the trees. The trees derive no known benefits from the dwarf mistletoes. Which of the following best describes the interactions between dwarf mistletoes and trees?

parasitism

Evidence shows that some grasses benefit from being grazed. Which of the following terms would best describe this plant-herbivore interaction?

mutualism

Which of the following would be most significant in understanding the structure of an ecological community?

determining which particular species are present

determining the kinds of interactions that occur among organisms of different species

determining how many species are present overall

determining the relative abundance of species

all of the above

Which of the following studies would a community ecologist undertake to learn about competitive interactions?

nitrate and phosphate uptake by various hardwood forest tree species

stomach analysis of brown trout and brook trout in streams where they coexist

selectivity of nest sites among cavity-nesting songbirds

the grass species preferred by grazing pronghorn antelope and bison

all of the above

White-breasted nuthatches and Downy woodpeckers both eat insects that hide in the furrows of bark in hardwood trees. The Downy woodpecker searches for insects by hunting from the bottom of the tree trunk toward the top, whereas the white-breasted nuthatch searches from the top of the trunk down. These hunting behaviors best illustrate which of the following ecological concepts?

resource partitioning

Which statement best describes the evolutionary significance of mutualism?

Interaction increases the survival and reproductive rates of mutualistic species.

How might an ecologist test whether a species is occupying all of its fundamental niche or only a portion of it?

Observe if the species expands its range after the removal of a competitor.

Which of the following terms is used by ecologists to describe the community interaction where one organism makes the environment more suitable for another organism?

facilitation

How did Eugene Odum describe an ecological niche?

an organism's "profession" in the community

In a tide pool, 15 species of invertebrates were reduced to 8 after one species was removed. The species removed was likely a(n)

keystone species.

Elephants are not the most dominant species in African grasslands, yet they influence community structure. The grasslands contain scattered woody plants, but they are kept in check by the uprooting activities of the elephants. Take away the elephants, and the grasslands convert to forests or to shrublands. The newly growing forests support fewer species than the previous grasslands. Which of the following describes why elephants are the keystone species in this scenario?

Elephants exhibit a disproportionate influence on the structure of the community relative to their abundance.

According to bottom-up and top-down control models of community organization, which of the following expressions would imply that an increase in the size of a carnivore (C) population would negatively impact on its prey (P) population, but not vice versa?

P ← C

Which of the following is a likely explanation for why invasive species take over communities into which they have been introduced?

Invasive species are not held in check by the predators and agents of disease that have always been in place for native species.

Biomanipulation can best be described as

removing many of the organisms at the next higher trophic level so that the struggling trophic level below can recover.

Imagine five forest communities, each with 100 individuals distributed among four different tree species (W, X, Y, and Z). Which forest community would be most diverse?

25W, 25X, 25Y, 25Z

Why are food chains relatively short?

Longer chains are less stable and energy transfer between trophic levels is inefficient.

According to the nonequilibrium model,

communities are constantly changing after being influenced by disturbances.

In a particular case of secondary succession, three species of wild grass all invaded a field. By the second season, a single species dominated the field. A possible factor in this secondary succession was

inhibition

The 1988 Yellowstone National Park lodgepole pine forest fires were likely the result of

years of fire suppression by humans.

Why do moderate levels of disturbance result in an increase in community diversity?

Habitats are opened up for less competitive species.

Species richness increases

as we travel southward from the North Pole to the equator.

There are more species in tropical areas than in places more distant from the equator. This is probably a result of

more intense annual solar radiation.

Why do tropical communities tend to have greater species diversity than temperate or polar communities?

Tropical communities are generally older than temperate and polar communities.

Which of the following is a correct statement about the McArthur/Wilson Island Equilibrium Model?

Small islands receive few new immigrant species.

Which of the following best describes the consequences of white-band disease in Caribbean coral reefs?

Algal species take the place of the dead coral, and the fish community is dominated by herbivores.

Zoonotic disease

is caused by pathogens that are transferred from other animals to humans by direct contact or by means of a vector.

Which of the following studies would shed light on the mechanism of spread of H5N1 from Asia?

Perform cloacal or saliva smears of migrating waterfowl to monitor whether any infected birds show up in Alaska.

Why is a pathogen generally more virulent in a new habitat?

Hosts in new environments have not had a chance to become resistant to the pathogen through natural selection.

In terms of community ecology, why are pathogens often more virulent now than before?

Human activities are transporting pathogens into new habitats (or communities) at an unprecedented rate.

The oak tree pathogen Phytophthora ramorum has migrated 800 km in 15 years. West Nile virus spread from New York State to 46 other states in 5 years. The difference in the rate of spread is probably related to

the mobility of their hosts.