Biogeochemical Cycles Review

What is the only process that removes carbon from the atmosphere?

• combustion

• cellular respiration

• photosynthesis

• decomposition

Answer explanation

Photosynthesis is the only process that removes carbon dioxide from the atmosphere, as plants convert CO2 into oxygen and glucose using sunlight. The other processes listed either release carbon or do not remove it.

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SB5b

A particular golf course is using large amounts of nitrogen fertilizer. What process could move this nitrogen into a local stream?

• volatilization

• nitrogen fixation

• runoff

• ammonification

Answer explanation

Runoff is the process where excess water, often from rainfall or irrigation, carries nitrogen fertilizer from the golf course into local streams. This movement of water can lead to nutrient pollution in aquatic ecosystems.

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SB5b

What converts nitrogen into a useable form for plants and animals?

• bacteria

• fungi

• rain

Answer explanation

Bacteria play a crucial role in converting nitrogen from the atmosphere into a usable form for plants and animals through processes like nitrogen fixation. This makes them essential for the nitrogen cycle.

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SB5b

Fossil fuels emissions from vehicles and factories play a major role in which cycle?

• carbon

• water

• nitrogen

• phosphorus

Answer explanation

Fossil fuel emissions primarily release carbon dioxide (CO2), which is a key greenhouse gas. This process significantly impacts the carbon cycle, making 'carbon' the correct answer.

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SB5b

Carbon dioxide is added to the atmosphere by...

• Burning fossil fuels 

• Cellular respiration

• Decomposing organic matter

• All answers are correct

Answer explanation

Carbon dioxide is released into the atmosphere through various processes: burning fossil fuels, cellular respiration, and decomposing organic matter. Therefore, the correct answer is 'All answers are correct'.

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SB5b

In an ecosystem, what happens to the atoms of certain chemical elements, such as carbon, oxygen, and nitrogen?

• They move into and out of living systems.

• They are only found in abiotic factors.

• They move out of living systems and do not return.

• They move into living systems and remain there.

Answer explanation

In an ecosystem, atoms of elements like carbon, oxygen, and nitrogen cycle through living and non-living systems. They are constantly moving into and out of organisms, supporting life processes and returning to the environment.

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SB5b

The carbon in coal, oil, and natural gas came from

• the combustion of fossil fuels

• the remains of dead organisms

• carbon-fixing bacteria in swamp soil

• carbon dioxide dissolved in ocean water

Answer explanation

The carbon in coal, oil, and natural gas originates from the remains of dead organisms, primarily plants and animals, that have been subjected to heat and pressure over millions of years, forming fossil fuels.

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SB5b

Law of conservation of mass states that

• matter is neither created nor destroyed

• matter is destroyed

• matter is created

• matter does not change

Answer explanation

The law of conservation of mass states that in a closed system, matter is neither created nor destroyed during a chemical reaction. This means the total mass remains constant, making 'matter is neither created nor destroyed' the correct choice.

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SB5b

Which is the most abundant gas in the atmosphere?

• hydrogen

• oxygen

• helium

• nitrogen

Answer explanation

Nitrogen is the most abundant gas in the atmosphere, making up about 78% of it. In contrast, oxygen is around 21%, while hydrogen and helium are present in much smaller amounts.

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SB5b

Identify the cycle pictured.

• The Water cycle

• The Carbon cycle

• The Nitrogen cycle

• The Phosphorus cycle

Answer explanation

The Nitrogen cycle describes the process of nitrogen's movement through the atmosphere, soil, and living organisms. It includes nitrogen fixation, nitrification, and denitrification, making it essential for life.

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SB5b