AP Environmental Science : Ecosystems and Biology

Study concepts, example questions & explanations for AP Environmental Science

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Example Questions

Example Question #1 : Nitrogen Cycle

Which of the following is the major reservoir of nitrogen in the nitrogen cycle?

Possible Answers:

Bacteria

Soil

Plants

Atmoshpere

Animals

Correct answer:

Atmoshpere

Explanation:

Although all of the above are part of the nitrogen cycle, the major reservoir for nitrogen is the atmosphere. The atmosphere contains nitrogen gas which cannot be extracted by plants or animals from the atmosphere. From its reservoir in the atmosphere, nitrogen gas is combined with oxygen to  form nitrate and carried to Earth dissolved in rain. Nitrogen-fixing bacteria produce ammonia. This is absorbed by plants and other producers and incorporated into biological molecules that are passed through the trophic levels. Nitrate and ammonia are released by excretion or by decomposer bacteria. Other bacteria convert these molecules back to atmoshperic nitrogen, completing the cycle.

Example Question #1 : Nitrogen Cycle

With reference to the biogeochemical cycles, how do elements and matter flow in the environment? 

Possible Answers:

From a source to a sink

From a sink to a sink

From a source to a source

From a sink to a source

Correct answer:

From a source to a sink

Explanation:

A source is an organism or physical body that releases a certain compound or element. Through energy dynamics or physical manipulations of the environment, it reaches the sink. The sink is the receiver of the element and can act as another source for a different organisms or physical body. This is how matter travels in the environment, from pairs of source to sink dynamics. 

Example Question #1 : Nitrogen Cycle

Why can't plants utilize atmospheric nitrogen for their metabolic processes? 

Possible Answers:

Atmospheric nitrogen is poisonous to plants 

Plants cannot absorb nitrogen unless it is in the form of nitrates

Plants do not need nitrogen for their metabolic processes

It must first be fixed by cyanobacteria into ammonia 

Correct answer:

It must first be fixed by cyanobacteria into ammonia 

Explanation:

According to the principles of the Nitrogen cycle, plants can only absorb nitrogen in the form of ammonia. This is achieved by nitrogen-fixing bacteria that convert atmospheric nitrogen into a form usable by plants. Plants excrete nitrogen in the form of waste as nitrates which are absorbed by animals. 

Example Question #1 : Biochemical Cycles

The phosphorus cycle is fundamentally different from the nitrogen and sulfur cycles. How so?

Possible Answers:

Phosphorus is not fixed in the atmosphere by lightning.

Phosphorus is cycled back into the soil through precipitation.

The phosphorus cycle does not include a gaseous phase, resulting in no significant quantities of atmospheric phosphorus.

Phosphorus is not taken up by plants and is a strictly inorganic cycle.

Phosphorus does not enter the cycle from weathering of sediments and parent material.

Correct answer:

The phosphorus cycle does not include a gaseous phase, resulting in no significant quantities of atmospheric phosphorus.

Explanation:

The phosphorus cycle does not contain an atmospheric phase, while both the sulfur and nitrogen cycles do.

Example Question #1 : Phosphorus Cycle

Which of the following is the major reservoir for phosphorus in the phosphorus cycle?

Possible Answers:

Soil

Rainwater

Animals

Plants

Rock

Correct answer:

Rock

Explanation:

The reservoir of phosphorus in ecosystems is rock, where it is bound to oxygen in the form of phosphate. As phosphate-rich rocks are exposed and eroded, rainwater dissolves the phosphate. Dissolved phosphate is abosrbed through the roots of plants. Animals eat the plants and after they die decomposers return the phosphorus that remains in the dead bodies back to the soil and water. It may then be reincorporated into rock. 

Example Question #2 : Phosphorus Cycle

Which biogeochemical cycle is the only one without an atmospheric component? 

Possible Answers:

The sulfur cycle 

The phosphorus cycle

The nitrogen cycle

The carbon cycle

Correct answer:

The phosphorus cycle

Explanation:

All of the other cycles have at least one atmospheric component in their systems. The carbon cycle incorporates carbon dioxide in the photosynthesis portion of its cycle. The sulfur cycle incorporates gaseous sulfur dioxide when it is released by volcanic eruptions. The water cycle has the condensation of clouds in the atmosphere and the precipitation of those clouds as well. The nitrogen cycle incorporates atmospheric nitrogen gas before it is fixed by cyanobacteria. Only the phosphorus cycle does not have a phosphorus containing compound in the atmosphere that is essential for life on Earth. 

Example Question #1 : Biochemical Cycles

 

The hydrolytic cycle is driven by which of the following?

Possible Answers:

Oceans

Rivers

Rain

Solar energy

Atmosphere

Correct answer:

Solar energy

Explanation:

The water cycle remains in the form of water throughout the cycle. The major reservoir of water is the ocean. The water cycle is driven by solar energy which evaporates water, and by gravity, which draws water back to Earth in the form of precipitation from water vapor in the atmosphere.

Example Question #1 : Water Cycle

Which answer choice a pair of terms that are the most similar in reference to the water cycle? 

Possible Answers:

Precipitation and runoff

Condensation and percolation

Precipitation and percolation

Transpiration and evaporation

Correct answer:

Transpiration and evaporation

Explanation:

Transpiration is the evaporation of water from plants. Both terms can be defined as the conversion of liquid water on Earth into atmospheric water vapor. Condensation is the formation of clouds from water vapor. Precipitation is the release of water from clouds down towards the earth in the form of rain, hail, sleet or snow. Percolation is the seeping of water through the ground into groundwater sources like aquifers. Runoff is excess water on the superficial soil layers that cannot percolate into the ground. 

Example Question #1 : Carrying Capacity

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

Possible Answers:

density-dependent, density-independent

none of these

density-independent, density-independent

density-independent, density-dependent

density-dependent, density-dependent

Correct answer:

density-dependent, density-independent

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.

Example Question #2 : Carrying Capacity

How is "cultural carrying capacity" different from "biological carrying capacity?"

Possible Answers:

Cultural carrying capacity predicts which human populations (depending on factors such as location, weather, and level of city planning) are most likely to develop a set of customs and laws. Biological carrying capacity describes the carrying capacity of each household in the community. 

Cultural carrying capacity describes the number of individuals that can exist alongside one another at a reasonable standard of living. Biological carrying capacity describes which species are able to coexist in a niche.

Cultural carrying capacity predicts the amount of "melting pot influence" that a society can withstand while still holding on to cultural beliefs and traditions. Biological carrying capacity describes how many individuals can survive. 

Cultural carrying capacity describes the number of individuals that can exist alongside one another at a reasonable standard of living. Biological carrying capacity describes how many individuals can survive.

Cultural carrying capacity describes the ability of a human population to thrive and create culture in meager circumstances. Biological carrying capacity describes how many individuals can survive. 

Correct answer:

Cultural carrying capacity describes the number of individuals that can exist alongside one another at a reasonable standard of living. Biological carrying capacity describes how many individuals can survive.

Explanation:

Cultural carrying capacity suggests that humans have secondary needs, such as entertainment, palatable food, and mental/spiritual development. These non-vital resources can only be spread equally among a population of a limited size. Cultural carrying capacity describes the limitation on population size after taking into account these factors. 

A frequent questions asked by sustainability scientists is: Should the optimum sustainable population be based on cultural carrying capacity? Many would agree yes, for the reason that when cultural capacity is transgressed, living conditions spiral downwards and life is reduced to the struggle for mere survival. In such conditions, human inventiveness and creativity become obsolete.

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