AP Biology : Understanding Ecosystems

Study concepts, example questions & explanations for AP Biology

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Example Questions

Example Question #2111 : Ap Biology

The sea otter plays an important role in controlling the sea urchin population in the Pacific Ocean. While they are not abundant in numbers, they play a vital role. The sea otter is an example of which of the following concepts?

Possible Answers:

Dominant species

Ecosystem engineers 

Commensalism 

Resource partitioning 

Keystone species

Correct answer:

Keystone species

Explanation:

The sea otter is an example of a keystone species. Keystone species are not abundant in the community, however they have a strong control on community structure because their ecological roles are so important. On the other hand, dominant species are those that are most abundant in their communities and have the highest biomass. The dominant species competitively exploits resources and avoid predation, giving them an advantage and allows them to grow large in number. Ecosystem engineers are species that dramatically alter their environment by changing its physical characteristics. 

Example Question #22 : Ecology

Two types of mosses grow separately. However, when they are put in the same environment and forced to live together, one of the mosses goes extinct. This is an example of which of the following?

Possible Answers:

Resource partitioning 

Character displacement

Adaptation

Ecological niche

Competitive exclusion

Correct answer:

Competitive exclusion

Explanation:

Competitive exclusion is when an inferior competitor is eliminated. In the moss example, the moss that is able to use resources more efficiently and reproduce quicker will beat out the less competitive moss. An ecological niche is the sum of a species’ use of the biotic and abiotic resources in its environment. Resource partitioning is the differentiation of niches that allows similar species to coexist in a community. If one of the mosses could adapt to use different resources, the two species could coexist together. Character displacement has to do with speciation. It refers to the tendency for character traits to diverge more in sympatric populations rather than allopatric populations.  

Example Question #21 : Understanding Ecosystems

Forest 1 has A, B, C, and D trees. There are five A trees, nine B trees, ten C tree, and six D trees. Forest 2 has A, C, and D trees. There are ten A trees, fourteen C trees, and seven D trees. Forest 1 demonstrates __________ over forest 2.  

Possible Answers:

greater biomass only

species diversity only

species richness only

species diversity and species richness

species diversity, species richness, and greater biomass

Correct answer:

species diversity and species richness

Explanation:

Species diversity is the variety of organisms that make up a community. There are two parts of species diversity: species richness and relative abundance. Species richness refers to the number of different species in the community. In this example, forest 1 has greater species richness and diversity over forest 2.  

Example Question #21 : Ecology

A seed that normally plants itself in the countryside is carried by the wind and plants itself in a forest. There, the seed grows and multiplies, competitively excluding many other native plant species. In the forest, this seed is an example of which of the following?

Possible Answers:

Homologous structures

Species diversity 

Invasive species

Parasitism

Herbivory 

Correct answer:

Invasive species

Explanation:

Invasive species are organisms that become established outside their native range. In this example, the seed’s native range is the countryside. However, when it is carried by the wind to the forest (an environment outside its native range), it plants itself and establishes a population there. The seed is an example of an invasive species. 

Example Question #2113 : Ap Biology

Where does primary succession occur?

Possible Answers:

A currently inhabited environment

A previously inhabited environment 

None of these

An environment lacking plant and animal life

Correct answer:

An environment lacking plant and animal life

Explanation:

Primary succession is the colonizing of a new environment that lacks organisms and plant life. Primary succession is different from secondary succession; secondary succession is the colonizing of an environment that once supported life but was abandoned due to an ecological disturbance. An example of this is the colonizing of new land formed by lava flow.

Example Question #2112 : Ap Biology

Which of the following is not considered to be a component of an ecosystem?

Possible Answers:

Biotic organisms

Abiotic components

Interactions between organisms and the environment

Limited to one species

Correct answer:

Limited to one species

Explanation:

Ecosystems are described as a community of organisms and their interactions between themselves and the environment. Ecosystems include abiotic and biotic components of the environment and are not limited to one species.

Example Question #21 : Ecology

Which of the following choices would most likely be characterized as abiotic?

Possible Answers:

Bird

Bacteria cell

Rock 

Leaf on a plant

Correct answer:

Rock 

Explanation:

The term “abiotic” refers to the nonliving components of the environment; therefore, a rock would be characterized as an abiotic part of the environment.

Example Question #21 : Ecology

Which of the following is an internal factor that impacts ecosystems?

Possible Answers:

Availability of resources

Presence of species

Frequency of disturbances

All of these

Correct answer:

All of these

Explanation:

Ecosystems are communities of abiotic and biotic components that interact together in the same environment. Ecosystems are controlled by both internal and external factors. Internal factors that control ecosystems include the availability of limiting resources, species presence, and disturbance.

Example Question #22 : Ecology

Which of the following is an external factor that controls ecosystems?

Possible Answers:

Frequency of disturbances

Climate

Availability of resources

None of these

Correct answer:

Climate

Explanation:

Ecosystems are communities of abiotic and biotic components that interact together in the same environment. Ecosystems are controlled by both internal and external factors. External factors that impact ecosystems include but are not limited to the invasion of non-native species, climate, and time.

Example Question #23 : Ecology

Which of the following is true regarding keystone species?

Possible Answers:

There will be no effect if a keystone species is removed from an ecosystem

The presence of a keystone species collapses the ecosystem

They are always the most abundant species in an ecosystem

Keystone species have a large effect on the ecosystem

Correct answer:

Keystone species have a large effect on the ecosystem

Explanation:

Despite their relatively small abundance, keystone species have a large impact on the environment in which they inhabit. If a keystone species is removed from an ecosystem, then there may be a large change in ecosystem’s stability.

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