AP Environmental Science : Phosphorus Cycle

Study concepts, example questions & explanations for AP Environmental Science

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Example Questions

Example Question #1 : Phosphorus Cycle

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

Possible Answers:

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

Phosphorus is cycled back into the soil through precipitation.

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

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

Phosphorus is not fixed in the atmosphere by lightning.

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

Rock

Animals

Rainwater

Plants

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 phosphorus cycle

The carbon cycle

The nitrogen cycle

The sulfur 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. 

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