Understanding the Nitrogen Cycle

Why can't plants and animals directly use nitrogen gas from the atmosphere?

• Because nitrogen gas is too heavy to be absorbed.

• Because nitrogen gas is only available in the ocean.

• Because nitrogen gas is inert due to its triple bond.

• Because nitrogen gas is toxic to plants and animals.

Which of the following biological molecules contain nitrogen?

• Proteins

• Lipids

• Water

• Carbohydrates

What is the role of nitrogen-fixing bacteria in the nitrogen cycle?

• They oxidize ammonia into nitrites.

• They decompose dead plants and animals.

• They convert nitrates into nitrogen gas.

• They convert nitrogen gas into ammonium or nitrates.

What is the process of converting ammonium into nitrites and then nitrates called?

• Ammonification

• Denitrification

• Nitrification

• Nitrogen fixation

Which type of plants have root nodules that help in nitrogen fixation?

• Non-leguminous plants

• Leguminous plants

• Deciduous plants

• Coniferous plants

What happens to nitrogen when plants and animals die?

• It remains unchanged in the soil.

• It is absorbed directly by other plants.

• It is converted into ammonia by decomposers.

• It is released as nitrogen gas immediately.

Why is denitrification undesirable in agriculture?

• It increases soil acidity.

• It leads to the loss of nitrogen from the soil.

• It causes soil erosion.

• It promotes weed growth.

What condition promotes denitrification in soil?

• High temperatures

• High oxygen levels

• Dry soil conditions

• Waterlogged soil

What is the purpose of plowing the soil in agriculture?

• To aerate the soil and prevent denitrification

• To increase soil acidity

• To prevent soil erosion

• To increase soil temperature

In an exam, what must be specified when discussing decomposers breaking down dead matter?

• The size of the decomposers

• The color of the plant matter

• The temperature of the environment

• The nitrogen-containing compound