Community Ecology Practice Questions

Correct answer: Commensalism

Commensalism is a +/0 interaction. A classic example is cattle egrets feeding on insects stirred up by grazing livestock; the birds get food while the cattle are unaffected.

Correct answer: Primary succession

Primary succession starts on bare rock or newly formed land where there is no pre-existing soil or organic matter. Pioneer species like lichens and mosses are typically the first to colonize these harsh environments.

Correct answer: Share the same limiting resource

Gause's Law states that two species with identical niches cannot coexist. The more efficient competitor will eventually eliminate the other unless one species evolves to use different resources.

Correct answer: A species with an outsized ecological impact relative to its abundance

Keystone species, like sea otters or wolves, maintain the structure and biodiversity of an ecosystem. Their removal often leads to a dramatic shift or collapse of the entire community structure.

Correct answer: Resource partitioning

Resource partitioning allows similar species to coexist by using different parts of a resource or operating at different times. By dividing the niche, they reduce direct competition for the same food source.

Correct answer: Batesian mimicry

In Batesian mimicry, a 'cheat' species evolves to look like a dangerous one. An example is the non-venomous king snake mimicking the color patterns of the highly venomous coral snake.

Correct answer: Secondary succession

Secondary succession occurs in areas where a community previously existed but was disturbed. Because soil and seeds often remain, this process is much faster than primary succession.

Correct answer: Mutualism

Mutualism is an interaction that increases the fitness of both participants. Examples include pollinators getting nectar while plants achieve fertilization, or gut bacteria aiding digestion in mammals.

Correct answer: Climax community

The climax community is the terminal stage of succession for a specific climate and geography. It is characterized by species that are highly efficient competitors and can tolerate the conditions they themselves have helped create.

Correct answer: Reducing the population of a dominant competitor

Predators often prey on the most abundant species. By keeping the population of a dominant competitor in check, they prevent that species from monopolizing resources, allowing weaker competitors to survive.

Correct answer: Competition

Competition is considered -/- because both parties expend energy and face increased risk or reduced resource access. Even the 'winner' of a competitive interaction is worse off than if the resource were uncontested.

Correct answer: Aposematic coloration

Aposematic coloration involves bright, high-contrast patterns (like the yellow and black of a wasp). It serves as a visual signal to predators that the organism is dangerous, toxic, or distasteful.

Correct answer: Two or more harmful species resemble each other

Mullerian mimicry occurs when multiple unpalatable species share a similar warning pattern. This reinforces the predator's learning process, as any encounter with any of the species teaches the predator to avoid all of them.

Correct answer: Species richness

Species richness is a simple count of the total number of distinct species. It does not take into account how many individuals of each species are present, which is known as species evenness.

Correct answer: Inside the body of their host

Endoparasites, such as tapeworms or malaria-causing Plasmodium, inhabit the internal organs or bloodstream of the host. Ectoparasites, like ticks or lice, live on the external surface.

Correct answer: Ecosystem engineer

Ecosystem engineers, such as beavers building dams or corals building reefs, physically modify the landscape. These changes create new niches and habitats that support a wider variety of other organisms.

Correct answer: Individuals of different species

Interspecific competition involves members of different species vying for the same limited resource. Intraspecific competition occurs between members of the same species.

Correct answer: Rapid growth and high dispersal rates

Pioneer species are adapted for quick colonization of disturbed areas. They typically produce many small, easily dispersed seeds or spores and grow rapidly to establish themselves before more competitive species arrive.

Correct answer: Character displacement

Character displacement is the evolutionary divergence of traits that reduces competition. When two species live together, natural selection favors individuals that are different from the competitor, leading to distinct physical differences.

Correct answer: Parasitism

This is a +/- interaction where the tick (parasite) gains nutrients at the expense of the dog (host). Unlike predators, parasites typically do not kill their host immediately, as they rely on the host for long-term survival.