Ecology SOL Unit 3.4 - Nitrogen Cycle

What percentage of the atmosphere is nitrogen?

• 50%

• 78%

• 25%

• 90%

Answer explanation

Nitrogen makes up about 78% of the Earth's atmosphere, making it the most abundant gas. The other options are incorrect as they significantly underestimate or overestimate nitrogen's presence.

Which form of nitrogen is found in the atmosphere?

• Nitrates (NO₃)

• Nitrites (NO₂)

• Ammonium (NH₄)

• Nitrogen gas (N₂)

Answer explanation

The atmosphere primarily consists of nitrogen gas (N₂), which makes up about 78% of the air we breathe. Nitrates, nitrites, and ammonium are forms of nitrogen found in soil and water, not in the atmosphere.

What is the first step of the nitrogen cycle?

• Nitrification

• Nitrogen Assimilation

• Nitrogen Fixation

• Denitrification

Answer explanation

The first step of the nitrogen cycle is Nitrogen Fixation, where atmospheric nitrogen is converted into a usable form by bacteria, making it available for plants and initiating the cycle.

During nitrification, ammonium (NH₄) is converted into what?

• Nitrogen gas (N₂)

• Nitrates (NO₃)

• Nitrites (NO₂)

• Ammonia (NH₃)

Answer explanation

During nitrification, ammonium (NH₄) is first converted to nitrites (NO₂) and then to nitrates (NO₃). Therefore, the correct answer is nitrates (NO₃), which are the final products of this process.

Tags

NGSS.MS-LS2-3

Drag and drop the terms to match the steps of the Nitrogen Cycle correctly.

a

b

c

d

e

Ammonification

Nitrogen Assimilation

Nitrogen Fixation

Nitrification

Denitification

Tags

NGSS.MS-LS2-1

NGSS.MS-LS2-3

What do plants absorb from the soil during nitrogen assimilation?

• Nitrogen gas (N₂)

• Nitrates (NO₃)

• Ammonium (NH₄)

• Nitrites (NO₂)

Answer explanation

During nitrogen assimilation, plants primarily absorb nitrates (NO₃) from the soil. Nitrates are a key form of nitrogen that plants can utilize for growth, making this the correct answer.

What process involves decomposers turning nitrogen back into ammonium?

• Nitrogen Fixation

• Nitrogen Ammonification

• Nitrogen Assimilation

• Nitrogen Nitrification

Answer explanation

Nitrogen Ammonification is the process where decomposers break down organic matter, converting nitrogen back into ammonium. This is a key step in the nitrogen cycle, facilitating nutrient recycling in ecosystems.

Tags

NGSS.MS-LS2-3

What happens during nitrogen denitrification?

• Nitrogen is fixed into the soil.

• Nitrites turn back into atmospheric nitrogen.

• Ammonium is converted into nitrites.

• Nitrogen is absorbed by plants.

Answer explanation

During nitrogen denitrification, nitrites are converted back into atmospheric nitrogen, completing the nitrogen cycle. This process helps reduce excess nitrogen in the soil, making 'Nitrites turn back into atmospheric nitrogen' the correct choice.

How does fertilizer affect the nitrogen cycle?

• It reduces nitrogen in the soil.

• It releases more nitrogen into the soil and atmosphere.

• It converts nitrogen into oxygen.

• It has no effect on the nitrogen cycle.

Answer explanation

Fertilizers often contain nitrogen, which can increase nitrogen levels in the soil. Additionally, some fertilizers can lead to nitrogen being released into the atmosphere through processes like volatilization, thus affecting the nitrogen cycle.

Tags

NGSS.HS-ESS3-1