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

• 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

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

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

Answer explanation

The correct sequence in the carbon cycle is plants take in carbon dioxide and produce glucose → animals consume plants → animals break down glucose and release carbon dioxide.

Tags

NGSS.MS-LS1-6

NGSS.MS-LS2-3

In the respiration-photosynthesis cycle shown above, what are the reactants of photosynthesis that belong in box 2?

• glucose and oxygen

• protein and nucleic acids

• carbon dioxide and water

• ATP and methane

Answer explanation

The reactants of photosynthesis that belong in box 2 are carbon dioxide and water, as they are used in the process to produce glucose and oxygen.

Tags

NGSS.MS-LS1-6

When glucose molecules are broken down, energy is released, and carbon dioxide and water are produced. What is this process called?

• glycolysis

• nitrogen fixation

• cellular respiration

• photosynthesis

Answer explanation

When glucose molecules are broken down, energy is released, and carbon dioxide and water are produced, which is known as cellular respiration.

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NGSS.MS-LS1-7

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

• carbon dioxide in the atmosphere

• carbon compounds stored in fossil fuels

• carbon compounds in the soil

• dissolved carbon dioxide in the biosphere

Answer explanation

The primary source of carbon in living things is carbon dioxide in the atmosphere.

Tags

NGSS.HS-LS2-5

Which substance is removed from the atmosphere so that plants can carry out photosynthesis?

• carbon dioxide

• nitrogen

• water vapor

• oxygen

Answer explanation

Plants remove carbon dioxide from the atmosphere to carry out photosynthesis, converting it into oxygen and glucose.

Tags

NGSS.MS-LS1-6

Using another simulation, the researchers estimated that the changes in the area burned by wildfires have increased the amount of carbon stored in the biosphere by approximately 1.3×10^8 metric tons of carbon per year between 1960 and 2009. Which of the following argument and evidence pairs best explains this finding?

• The decrease in combustion has reduced wildfire-related CO2 output to the atmosphere and increased the vegetation available to uptake atmospheric CO2. Evidence: The PD + LUC model suggests a decrease in area burned by wildfires since 1960, relative to that in 1850.

• The increase in wildfires has decreased the output of CO2 to the atmosphere by decreasing the amount of vegetation available for respiration and decomposition. Evidence: The model that only includes PD suggests an increase in the area burned by wildfires since the 1850s.

• The increase in combustion has increased the CO2 available for photosynthesis by increasing wildfire-related CO2 output to the atmosphere. Evidence: The PD + LUC model suggests an increase in area burned by wildfires since 1960, relative to that in 1850.

• The decrease in wildfires has increased the rate at which carbon on land is transferred to atmospheric CO2 by increasing the amount of vegetation available for respiration and decomposition. Evidence: The model that only includes LUC suggests a decrease in the area burned by wildfires since the 1850s.

Answer explanation

The decrease in combustion has reduced wildfire-related CO2 output to the atmosphere and increased the vegetation available to uptake atmospheric CO2. Evidence: The PD + LUC model suggests a decrease in area burned by wildfires since 1960, relative to that in 1850.

Tags

NGSS.MS-ESS2-1

NGSS.MS-ESS2-2

NGSS.MS-LS2-3

NGSS.MS-LS2-4

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?

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

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

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

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

Answer explanation

The total amount of carbon in the system remains constant because carbon cycles through the atmosphere, hydrosphere, biosphere, and geosphere.

Tags

NGSS.MS-ESS2-1

NGSS.MS-LS2-3

Which statement best describes why the carbon cycle is important to life?

• Without carbon being cycled, there would soon be no carbon left on Earth, so organisms would not be able to get nutrients.

• Without a way to remove carbon from the atmosphere, plants would be harmed by the accumulation of atmospheric carbon dioxide.

• Without carbon being returned to the atmosphere, plants eventually would not have the carbon dioxide they need.

• Without a way to create more carbon, plants and animals would soon have to survive only on nutrients that do not contain carbon.

Answer explanation

Without carbon being returned to the atmosphere, plants eventually would not have the carbon dioxide they need.

Tags

NGSS.MS-ESS2-1

NGSS.MS-LS2-3

An algal bloom is a rapid increase in the population of algae in an aquatic system. These blooms, which may be prompted by increases in water temperature or an excess of nutrients, can have a variety of effects on an ecosystem.

Scientists examined how an algal bloom affects a lake ecosystem. The scientists recorded the algae population density in the lake over a 29-day period in the summer. Algae population density was estimated from the concentration of chlorophyll in the lake water. The scientists also recorded the dissolved carbon dioxide concentration and the dissolved oxygen concentration in the water during each sampling event. These results are shown in the table below.

Which of the following statements provides the best explanation for the scientists' findings?

• During the first 17 days, the CO2 concentration in the lake increased as algae converted inorganic carbon to CO2 through photosynthesis.

• After day 17, the CO2 concentration in the lake increased as carbon stored in algae was returned to the water through decomposition.

• During the first 17 days, the CO2 concentration in the lake decreased as the growing algae population consumed CO2 through respiration.

• After day 17, the CO2 concentration in the lake increased as the algae population produced CO2 through photosynthesis.

Answer explanation

After day 17, the CO2 concentration in the lake increased as carbon stored in algae was returned to the water through decomposition.

Tags

NGSS.MS-LS1-6

NGSS.MS-LS2-3

NGSS.MS-LS2-4

Which of the following can be determined based on this model?

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

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

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

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

Answer explanation

Both plants and animals release carbon dioxide into the atmosphere during cellular respiration, as shown in the model.

Tags

NGSS.MS-ESS2-1

NGSS.MS-LS2-3