The Carbon Cycle

Study the simplified diagram of the carbon cycle shown. Which processes (shown in red) are carried out within living organisms?

I. photosynthesis

II. decomposition

III. conversion

IV. combustion

V. respiration

• A. II and IV only

• B. I and V only

• C. I, III, and V only

• D. I, II, III, and V only

Models are often used to explain scientific knowledge or experimental results. A model of the carbon cycle is shown below. Which of the following can be determined based on this model?

• Dead organisms and waste products do not play any role within the carbon cycle.

• Both plants and animals release carbon dioxide into the atmosphere during cellular respiration.

• Factories do not emit any amount of carbon dioxide into the atmosphere.

• The atmosphere is the only reservoir on Earth that can store carbon in any form.

Why is it important for water to be recycled in an ecosystem?

• Recycling water allows organisms to create more water.

• Recycling water allows organisms to create less water.

• If water isn't recycled, there will be too much of it on Earth.

• The water cycle is a closed system, and recycling water is the only way to replenish it for an ecosystem.

In the carbon cycle, carbon is taken in by plants

• as ammonia in the process of assimilation.

• as water vapor in the process of photosynthesis.

• as carbon dioxide in the process of decomposition.

• as carbon dioxide in the process of photosynthesis.

The bodies of all living things are based on carbon. Which of the following is the primary source of carbon in living things?

• carbon compounds stored in fossil fuels

• dissolved carbon dioxide in the biosphere

• carbon compounds in the soil

• carbon dioxide in the atmosphere

Which of the following could be a sequence in the carbon cycle?

• animals break down glucose and release carbon dioxide → animals consume plants → plants take in carbon dioxide and produce glucose

• plants take in carbon dioxide and produce glucose → animals consume plants → animals break down glucose and release carbon dioxide

• animals consume plants → plants take in carbon dioxide and produce glucose → animals break down glucose and release carbon dioxide

• plants take in carbon dioxide and produce glucose → animals break down glucose and release carbon dioxide → animals consume plants

During cellular respiration, cells convert oxygen and glucose into carbon dioxide, water, and energy. How is this process related to that of photosynthesis?

• The products of photosynthesis are the reactants of cellular respiration.

• In photosynthesis, oxygen is inhaled, and carbon dioxide and water are exhaled.

• In photosynthesis, cells use ATP to convert insulin into glucose and carbon dioxide.

• Both photosynthesis and cellular respiration occur in a cell's mitochondria

The diagram below represents the carbon cycle. Which of the following best describes the total amount of carbon in the system made up of the Earth and its atmosphere?

• A. It remains constant because carbon cycles through the atmosphere, hydrosphere, biosphere, and geosphere.

• B. It remains constant because oxygen converts to carbon in the geosphere and hydrosphere.

• C. It continually decreases as carbon is used up during photosynthesis and trapped in the biosphere.

• D. It continually increases as carbon is produced during cellular respiration and trapped in the atmosphere.

Which of the following processes describes carbon moving from the atmosphere to the biosphere?

• A. photosynthesis

• B. decomposition

• C. cellular respiration

• D. combustion

In many areas on Earth, the carbon cycle is being influenced by an increase in the amount of fossil fuels being burned by humans. When fossil fuels are combusted, carbon dioxide is released into the atmosphere. Which of the following describes a possible effect that an increase in carbon dioxide in the atmosphere would have on an ecosystem?

• Animal productivity would increase because more carbon dioxide would be available for cellular respiration.

• All of the organisms would immediately die because carbon dioxide is poisonous to both plants and animals.

• Plant productivity would increase because more carbon dioxide would be available for photosynthesis.