Ecology Community Species Interactions Questions and Answers — Questions and Answers
Question 1: In a classic experiment, G.F. Gause cultured two species of Paramecium, P. aurelia and P. caudatum, in the same environment with a fixed amount of daily food. When grown together, P. aurelia thrived, while the P. caudatum population declined and eventually went extinct. This outcome is a direct example of which ecological principle?
- Resource partitioning
- Character displacement
- Competitive exclusion (Correct answer)
- Trophic cascade
Correct answer: Competitive exclusion
The competitive exclusion principle, also known as Gause's Law, states that two species competing for the same limited resources cannot coexist indefinitely in the same niche; one will eventually outcompete and eliminate the other. In this experiment, both Paramecium species competed for the same food source, and P. aurelia was the superior competitor, leading to the extinction of P. caudatum.
Question 2: Which of the following scenarios best illustrates the concept of resource partitioning?
- A lion pride successfully driving a clan of hyenas away from a recent kill.
- The reintroduction of wolves to an ecosystem leading to an increase in aspen trees due to reduced elk populations.
- Five species of coexisting warblers feeding on insects in different zones of the same spruce trees. (Correct answer)
- A harmless hoverfly evolving to have the same black and yellow coloration as a stinging wasp.
Correct answer: Five species of coexisting warblers feeding on insects in different zones of the same spruce trees.
Resource partitioning is the division of limited resources by species to help avoid competition in an ecological niche. The classic example of this is Robert MacArthur's study of warblers, where different species utilized different parts of the same tree (e.g., top branches, lower trunk) to forage for insects, thus minimizing direct competition and allowing coexistence.
Question 3: In a Pacific kelp forest ecosystem, sea otters prey on sea urchins. The sea urchins, in turn, graze on kelp. The presence of sea otters maintains a healthy kelp forest, which supports a wide variety of other species. Based on this role, the sea otter is best described as a(n):
- Apex predator
- Keystone species (Correct answer)
- Indicator species
- Foundation species
Correct answer: Keystone species
A keystone species is a species that has a disproportionately large effect on its environment relative to its abundance. The sea otter is a classic example; by controlling the sea urchin population, it prevents the overgrazing of kelp, thereby maintaining the entire kelp forest structure and the diverse community it supports.
Question 4: A non-venomous kingsnake has coloration and banding patterns very similar to the highly venomous coral snake. Predators that have learned to avoid the dangerous coral snake will also avoid the harmless kingsnake. This type of defensive adaptation is known as:
- Commensalism
- Müllerian mimicry
- Aposematism
- Batesian mimicry (Correct answer)
Correct answer: Batesian mimicry
Batesian mimicry is a form of mimicry where a harmless species has evolved to imitate the warning signals of a harmful species directed at a common predator. The kingsnake (the mimic) benefits from looking like the venomous coral snake (the model) because predators avoid it.
Question 5: The removal of a top predator, such as the grey wolf, from an ecosystem results in a dramatic increase in the elk population. This leads to the overgrazing of willow and aspen trees, which in turn negatively affects beaver populations that rely on these trees for food and dam construction. This chain of indirect effects across multiple trophic levels is called a:
- Competitive exclusion event
- Symbiotic shift
- Trophic cascade (Correct answer)
- Niche displacement
Correct answer: Trophic cascade
A trophic cascade describes the indirect effects that a predator can have on the rest of its ecosystem by controlling its prey population. The removal or addition of a top predator triggers reciprocal changes down the food chain, affecting herbivores and the primary producers they consume.
Question 6: Cattle egrets are birds that are often found foraging in fields among cattle. The cattle's movements stir up insects from the ground, which the egrets then eat. The cattle are unaffected by the presence of the egrets. What type of symbiotic relationship does this represent?
- Mutualism
- Parasitism
- Competition
- Commensalism (Correct answer)
Correct answer: Commensalism
Commensalism is a symbiotic relationship where one organism benefits and the other is neither harmed nor helped. In this scenario, the cattle egrets benefit by getting an easy source of food, while the cattle are not significantly affected by their presence.
Ecology Community Species Interactions Questions and Answers
In a classic experiment, G.F.
Gause cultured two species of Paramecium, P. aurelia and P. caudatum, in the same environment with a fixed amount of daily food.
When grown together, P. aurelia thrived, while the P. caudatum population declined and eventually went extinct.
This outcome is a direct example of which ecological principle?