AP Environmental Science : Biochemical Cycles

Study concepts, example questions & explanations for AP Environmental Science

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Example Questions

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Example Question #1 : Biochemical Cycles

Which of the following steps is not part of the carbon cycle?

Possible Answers:

Photosynthesis

Extraction

Combustion

Respiration

Transpiration

Correct answer:

Transpiration

Explanation:

Transpiration concerns the process through which water is carried through plants from roots to small pores in leaves, where it evaporates into the atmosphere. Thus transpiration is not a part of the carbon cycle, which concerns the biochemical exchange of carbon. 

Example Question #125 : Ecosystems And Biology

All of the following are Carbon sinks in the Carbon Cycle except...? 

Possible Answers:

The Ocean

The Atmosphere

Animals

Plants

Correct answer:

The Atmosphere

Explanation:

The Atmosphere is largely the source of Carbon in the Carbon cycle. Plants utilize photosynthesis to convert atmospheric Carbon Dioxide into Glucose. Animals consume this Glucose and store it in their bodies until they die. the Ocean hosts a large amount of dissolved Carbon Dioxide gas and has Calcium Carbonate as a storage place in oceanic organisms like coral. 

Example Question #1 : Carbon Cycle

Which of these is a type of biogeochemical cycles?

Possible Answers:

Carbon cycle

Phosphorous cycle

Hydraulic cycle

All of these

Nitrogen cycle

Correct answer:

All of these

Explanation:

All of these are biogeochemical cycles:

Carbon cycle - plants and animals consume carbon dioxide and release carbon dioxide during decomposition or respiration, then the carbon dioxide returns to the atmosphere.

Phosphorus cycle - similar to the carbon cycle, plants and animals consume phosphorous and release it during decomposition. Then the phosphorous returns to the ground and waterways by way of bacteria and processes such as mineralization. 

Nitrogen cycle - this is the most complicated biogeochemical cycles. This is because it takes place in multiple situations, including: nitrogen fixation, nitrification, denitrification, and ammonification.

Hydraulic cycle - the water cycle. Water evaporates, wind moves air (and water), precipitation occurs.

Example Question #1 : Biochemical Cycles

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

Possible Answers:

Atmoshpere

Plants

Bacteria

Animals

Soil

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 source

From a source to a source

From a sink to a sink

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 do not need nitrogen for their metabolic processes

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

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 #2 : Biochemical Cycles

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

Possible Answers:

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

Phosphorus is cycled back into the soil through precipitation.

Phosphorus is not fixed in the atmosphere by lightning.

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

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

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:

Animals

Plants

Soil

Rock

Rainwater

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 carbon cycle

The phosphorus cycle

The nitrogen 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 #2 : Biochemical Cycles

 

The hydrolytic cycle is driven by which of the following?

Possible Answers:

Atmosphere

Oceans

Rain

Rivers

Solar energy

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.

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