Question 1

The most plausible hypothesis to explain why species richness is higher in tropical than in temperate regions is that

Accepted Answer

Tropical regions generally have more available water and higher levels of solar radiation, which leads to greater primary productivity and more diverse habitats that can support greater species richness.

Question 2

The principle of competitive exclusion states that

Accepted Answer

The principle of competitive exclusion states that two species that have exactly the same niche cannot coexist in a community. This is because they would be competing for the same resources and one species would eventually outcompete and displace the other. Therefore, only one species can occupy a particular niche in a community.

Question 3

According to the island equilibrium model, species richness would be greatest on an island that is

Accepted Answer

The island equilibrium model states that species richness on an island is determined by the balance between immigration and extinction rates. Large islands have higher immigration rates, while small islands have higher extinction rates. Islands close to a mainland also have higher immigration rates. Therefore, a large island close to a mainland would have the highest species richness according to the island equilibrium model.

Question 4

Predators that are keystone species can maintain species diversity in a community if they

Accepted Answer

Keystone species, such as predators, have a disproportionate impact on their community. By preying on the dominant species, they prevent any one species from gaining too much of an advantage and reduce competition among other species. This helps maintain a diverse community.

Question 5

Based on the intermediate disturbance hypothesis, a community's species diversity is increased by

Accepted Answer

The intermediate disturbance hypothesis states that moderate levels of disturbance can promote species coexistence and increase biodiversity by preventing competitively dominant species from excluding less competitive species. Therefore, choice C, moderate levels of disturbance, best fits the hypothesis. Choices A and D would either result in too much disturbance or elimination of disturbance, both of which would negatively impact species diversity. Choice B, stable conditions with no disturbance, would not allow for any opportunities for new species to establish themselves and colonize the community.

Question 6

The feeding relationships among the species in a community determine the community's

Accepted Answer

The trophic structure refers to the feeding relationships among the species in a community, including the flow of energy and nutrients from one level to the next. Therefore, the feeding relationships determine the trophic structure of the community. Choices A, B, and C are not accurate descriptors of the community based solely on the feeding relationships among its species.

Question 7

Red-cheeked salamanders are partially protected from predators because of cardiac glycosides they produce from glands on their back. When ingested, cardiac glycosides disrupt normal heart rhythms. A different salamander species, the imitator salamander, also has red cheek patches, but does not produce cardiac glycosides. It does gain protection from predators that have learned to avoid red-cheeked salamanders. How does this relationship affect the population dynamics of both species?

Accepted Answer

The answer of Red-cheeked salamanders are partially protected from predators...

Question 8

Which of the following could qualify as a top-down control on a grassland community?

Accepted Answer

Grazing intensity by bison is a top-down control because it involves the influence of a higher trophic level (the grazers) on the abundance and diversity of plant species in the community. The other options are all bottom-up controls because they involve abiotic factors (rainfall, temperature, soil nutrients) that influence the growth and productivity of plants from the bottom of the food chain up.

Question 9

Food chains are sometimes short because

Accepted Answer

The answer of Food chains are sometimes short because
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Question 10

Scientists interested in how populations interact within communities are attempting to determine the species diversity of an island under study. What kind of data would be most helpful to the scientists in determining diversity?

Accepted Answer

The number of different species on the island and the size of the population of each species would be the most helpful data in determining species diversity. This data would allow the scientists to calculate species richness (the number of different species present) and abundance (the number of individuals within each species).

Question 11

The oak tree fungal pathogen, Phytophthora ramorum, has migrated 800 kilometers 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 ________.

Accepted Answer

The difference in the rate of spread is likely related to the mobility of their hosts. Phytophthora ramorum is a fungus that infects oak trees, which are relatively immobile, while West Nile virus is spread by mosquitoes, which are highly mobile. Therefore, the virus is able to spread much more quickly than the fungus.

Quiz 54: Community Ecology