Organismal Ecology

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GRE Subject Test: Biology › Organismal Ecology

Questions 1 - 10
1

Hummingbirds use their long beaks to drink nectar from flowers. In turn, they carry the pollen from flower to flower, assisting the reproduction of the flowers.

What relationship does this describe?

Mutualism

Co-evolution

Parasitism

Resource Partitioning

Competitive Exclusion

Explanation

Coevolution is a process by which two or more species evolve in response to one another, and generally describes competing species. While the hummingbird and the flower may evolve due to this relationship, coevolution more freqeucntly describes the evolution of defense mechanisms in response to a predator-prey relationship. Parasitism is the relationship in which one species benefits at the expense of the host. This can sometimes lead to coevolution, depending on how the host reacts. Neither species is being harmed in the given scenario, so this is incorrect. Commensalism is when one species benefits, but the other species is not impacted. In this case, both the hummingbird and the flower are benefiting, so this is not our answer. Resource partitioning is when species evolve together to share resources in a sustainable way. The hummingbird is using a resource that the flower provides, but they are not "sharing" in the sense of the definition of resource partitioning. Competitive exclusion describes the phenomenon when two species share the same niche, and the stronger one forces out the weaker competitor.

Mutualism, the correct answer, describes a relationship wherein species exploit each other mutually. In this case, the hummingbird gains nutrition from the flower, and the flower gains a reproductive advantage from the hummingbird.

2

Hummingbirds use their long beaks to drink nectar from flowers. In turn, they carry the pollen from flower to flower, assisting the reproduction of the flowers.

What relationship does this describe?

Mutualism

Co-evolution

Parasitism

Resource Partitioning

Competitive Exclusion

Explanation

Coevolution is a process by which two or more species evolve in response to one another, and generally describes competing species. While the hummingbird and the flower may evolve due to this relationship, coevolution more freqeucntly describes the evolution of defense mechanisms in response to a predator-prey relationship. Parasitism is the relationship in which one species benefits at the expense of the host. This can sometimes lead to coevolution, depending on how the host reacts. Neither species is being harmed in the given scenario, so this is incorrect. Commensalism is when one species benefits, but the other species is not impacted. In this case, both the hummingbird and the flower are benefiting, so this is not our answer. Resource partitioning is when species evolve together to share resources in a sustainable way. The hummingbird is using a resource that the flower provides, but they are not "sharing" in the sense of the definition of resource partitioning. Competitive exclusion describes the phenomenon when two species share the same niche, and the stronger one forces out the weaker competitor.

Mutualism, the correct answer, describes a relationship wherein species exploit each other mutually. In this case, the hummingbird gains nutrition from the flower, and the flower gains a reproductive advantage from the hummingbird.

3

Eusocial insects, like many species of ants, are some of the most well known and successful social animals in the world. What factors are necessary for an insect species to be eusocial?

I. Cooperative brood care between different individuals

II. Division of labor by reproductive capability

III. Overlap of generations

IV. Adults care for their own offspring for some time

I, II, and III

I, II, III, and IV

I and II

III and IV

II only

Explanation

Eusociality is defined by options I, II, and III. A species must cooperate on brood care (think ants bringing food back to the colony), labor is divided by reproductive ability (think sterile worker bees and queens) and the generations must overlap so that the colony is maintained properly.

4

K-strategist populations are more commonly regulated by ____________ limiting factors, and r-strategist populations are regulated by ___________ limiting factors.

density-dependent, density-independent

density-independent, density-independent

density-independent, density-dependent

density-dependent, density-dependent

none of these

Explanation

K-strategist populations are more commonly regulated by density-dependent limiting factors. Their population sizes hover around a carrying capacity that is dependent on factors that increase in severity with the density of the population. On the other hand, r-strategist populations are regulated by density-independent limiting factors. They reproduce rapidly until a density-independent factor causes many of them to die.

5

K-strategist populations are more commonly regulated by ____________ limiting factors, and r-strategist populations are regulated by ___________ limiting factors.

density-dependent, density-independent

density-independent, density-independent

density-independent, density-dependent

density-dependent, density-dependent

none of these

Explanation

K-strategist populations are more commonly regulated by density-dependent limiting factors. Their population sizes hover around a carrying capacity that is dependent on factors that increase in severity with the density of the population. On the other hand, r-strategist populations are regulated by density-independent limiting factors. They reproduce rapidly until a density-independent factor causes many of them to die.

6

Eusocial insects, like many species of ants, are some of the most well known and successful social animals in the world. What factors are necessary for an insect species to be eusocial?

I. Cooperative brood care between different individuals

II. Division of labor by reproductive capability

III. Overlap of generations

IV. Adults care for their own offspring for some time

I, II, and III

I, II, III, and IV

I and II

III and IV

II only

Explanation

Eusociality is defined by options I, II, and III. A species must cooperate on brood care (think ants bringing food back to the colony), labor is divided by reproductive ability (think sterile worker bees and queens) and the generations must overlap so that the colony is maintained properly.

7

Detritivores employ an evolutionarily successful feeding strategy of animals, in which they feed primarily on other animals' waste. Why is this an efficient approach?

Dung is much easier to digest because its already been digested by another animal

Nutrient content is much richer in detritus

There is less competition for detritus than other resources

There are no special adaptations required to be a detritivore

There is more detritus than live biomass

Explanation

Detritivores are successful because it is much more efficient to digest dung because it doesn't require much extra digesting, as another animal has already done it. Detritivores can generally have a much less complicated digestive system and save themselves the energetically expensive process of digesting new plants or animals. Detritivores are also important to the ecosystem because they cycle the nutrients in dung back into the food chain. There is no evidence that detritivores experience less competition, nor that detritus is in excess to live organisms.

8

Which of the following most accurately describes a deme?

A group of individuals more genetically similar to each other than to other individuals, even if spatially isolated

A group of conspecific individuals separated demographically, genetically, or spatially from other groups

A set of individuals geographically isolated from other groups

A set of spatially disjunct populations in which some immigration still occurs

A collection of populations of organisms isolated genetically but still living in the same area and sharing many characteristics

Explanation

A deme is defined as a group of individuals more genetically similar to each other than to other individuals, even if spatially isolated. A group of conspecific individuals separated demographically, genetically, or spatially from other groups is a population**.** A set of spatially disjunct populations in which some immigration still occurs is a metapopulation**.** The other options are not well-defined in population ecology.

9

Which of the following most accurately describes a deme?

A group of individuals more genetically similar to each other than to other individuals, even if spatially isolated

A group of conspecific individuals separated demographically, genetically, or spatially from other groups

A set of individuals geographically isolated from other groups

A set of spatially disjunct populations in which some immigration still occurs

A collection of populations of organisms isolated genetically but still living in the same area and sharing many characteristics

Explanation

A deme is defined as a group of individuals more genetically similar to each other than to other individuals, even if spatially isolated. A group of conspecific individuals separated demographically, genetically, or spatially from other groups is a population**.** A set of spatially disjunct populations in which some immigration still occurs is a metapopulation**.** The other options are not well-defined in population ecology.

10

Detritivores employ an evolutionarily successful feeding strategy of animals, in which they feed primarily on other animals' waste. Why is this an efficient approach?

Dung is much easier to digest because its already been digested by another animal

Nutrient content is much richer in detritus

There is less competition for detritus than other resources

There are no special adaptations required to be a detritivore

There is more detritus than live biomass

Explanation

Detritivores are successful because it is much more efficient to digest dung because it doesn't require much extra digesting, as another animal has already done it. Detritivores can generally have a much less complicated digestive system and save themselves the energetically expensive process of digesting new plants or animals. Detritivores are also important to the ecosystem because they cycle the nutrients in dung back into the food chain. There is no evidence that detritivores experience less competition, nor that detritus is in excess to live organisms.

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