AP Biology : Understanding Eco-Chemical Cycles

Study concepts, example questions & explanations for AP Biology

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Example Questions

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Example Question #1 : Understanding Eco Chemical Cycles

Respiration and photosynthetic processes are ecologically linked to one another in which of the following processes?

Possible Answers:

Phosphorous cycle

Nitrogen cycle

Carbon cycle

Carbon cycle and oxygen cycle

Water cycle

Correct answer:

Carbon cycle and oxygen cycle

Explanation:

Both cellular respiration and photosynthesis are involved in the carbon cycle and the oxygen cycle. They both require carbon and oxygen in order to complete their mechanisms of action.

During photosynthesis, carbon is taken by the plant and converted into energy. As a result, oxygen is released. This oxygen can be used by cellular respiration to generate energy, which produces a carbon dioxide product. This carbon dioxide product can be recycled and eventually used for photosynthesis.

Example Question #81 : Ecology

Of the following components, which cannot be recycled in a stable ecosystem?

Possible Answers:

Oxygen

Nitrogen

Energy

Water

Hydrogen

Correct answer:

Energy

Explanation:

Energy, in an ecological context, refers to its flow in an ecosystem. Energy is passed from trophic level to trophic level; however, each time this occurs about ten percent of this energy is lost to the environment or as digested food. Energy is thus not recycled in this context.

In contrast, water, carbon, oxygen, nitrogen, and hydrogen are passed from one organism to another as organic material. This material is digested and incorporated into the organism's own biology, or released back into the ecosystem for continued use by other organisms in the environment. Energy can be passed from one organism to another in the form of chemical bonds and is released in the form of heat, but cannot be used by other organisms once it is returned to the environment and does not follow an ecological cycle.

Example Question #82 : Ecology

Which of the following is not involved in an eco-chemical cycle?

Possible Answers:

Nitrogen

Water

Iron

Carbon

Phosphorus

Correct answer:

Iron

Explanation:

Water, carbon, nitrogen, sulfur, and phosphorus have cyclic pathways that allowing them to flow within an ecosystem. Iron is not involved in very many ecological processes, and does not follow a defined chemical cycle.

Example Question #83 : Ecology

Which of the following is true regarding nitrogen in the atmosphere?

Possible Answers:

Nitrogen makes up most of the Earth's atmosphere

All of the atmospheric nitrogen can be used biologically 

There is no nitrogen in the atmosphere

There is unlimited nitrogen for use by ecosystems

Correct answer:

Nitrogen makes up most of the Earth's atmosphere

Explanation:

Nitrogen makes up most of the Earth’s atmosphere; however, this reserve of nitrogen is limited for biological use. Nitrogen exists in diatomic forms in the atmosphere and the process of nitrogen fixation frees atoms for biological use. As a result, nitrogen is a limiting resource in many ecosystems.

Example Question #84 : Ecology

What is the state of carbon in the atmosphere?

Possible Answers:

Carbon dioxide only

Neither carbon dioxide nor methane

Methane only

Both carbon dioxide and methane

Correct answer:

Both carbon dioxide and methane

Explanation:

In Earth’s atmosphere, carbon can be found in two forms: carbon dioxide and methane. Both are responsible for the greenhouse effect as they absorb and retain heat.

Example Question #2 : Understanding Eco Chemical Cycles

What happens to carbon in the atmosphere?

Possible Answers:

It remains unchanged in the atmosphere

It changes forms within the atmosphere

It leaves the atmosphere and enters the terrestrial biosphere

It rises in the atmosphere into the extraterrestrial biosphere

Correct answer:

It leaves the atmosphere and enters the terrestrial biosphere

Explanation:

Carbon leaves the atmosphere and enters the terrestrial biosphere through photosynthesis and dissolution. Thus, carbon enters bodies of water and plants, where it is incorporated into organisms as organic molecules. Then the different trophic levels will consume these organic molecules. Upon their death, the carbon will be recycled within the terrestrial biosphere.

Example Question #86 : Ecology

Carbon leaves the atmosphere through what processes?

Possible Answers:

Both photosynthesis and dissolution

Photosynthesis only

Dissolution only

Neither photosynthesis nor dissolution

Correct answer:

Both photosynthesis and dissolution

Explanation:

Carbon leaves the atmospheric biosphere and enters the terrestrial biosphere through photosynthesis and dissolution into bodies of water. Recall that carbon dioxide is a reactant of photosynthesis, and it gets converted into glucose. 

Example Question #87 : Ecology

What happens to carbon when it enters bodies of water?

Possible Answers:

It forms carbonic acid

It adds volume to a body of water

It forms carbonate

It forms water molecules

Correct answer:

It forms carbonic acid

Explanation:

When carbon enters into bodies of water through precipitation, it reacts with water to form carbonic acid. Carbonic acid then is absorbed into rocks in the sedimentary biosphere. Carbonic acid is very soluble in water, and is the form that most of carbon is in when dissolved in water.

Example Question #88 : Ecology

Recently, the amount of carbon in the atmosphere has increased. What human activity has directly caused this?

Possible Answers:

Technology advancements

Genetic engineering

An increase in the average lifespan

Burning of fossil fuels

Correct answer:

Burning of fossil fuels

Explanation:

The burning of fossil fuels has increased the amount of carbon in the atmosphere, contributing to the greenhouse effect and global warming. Burning fossil fuels mainly involves combustion reactions in which the fuel is oxidized, producing carbon dioxide and water. While the other answer choices may add to the carbon dioxide levels of the atmosphere, the question asks for a direct cause.

Example Question #89 : Ecology

In the terrestrial biosphere, where can carbon be found?

Possible Answers:

In all living organisms

In the soil

All of these

In inorganic forms

Correct answer:

All of these

Explanation:

In the terrestrial biosphere, carbon can be found in all living and dead organisms, stored in the soil, and in inorganic forms. Inorganic carbon refers to carbon in minerals and ores. It is often said that life on earth is carbon-based due to its versatility and ubiquity.

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