Biogeochemical Cycles

Nitrogen fixation is carried out mainly by

• humans

• plants

• animals

• bacteria

Burning fossil fuel has which effect in the carbon cycle?

• It removes carbon dioxide from the atmosphere.
• It puts carbon dioxide under the ground.
• It adds carbon dioxide to the atmosphere.
• It has no effect in the carbon cycle.

Which process takes carbon dioxide out of the atmosphere?

• respiration
• combustion
• decomposition
• photosynthesis

Which of the following add carbon dioxide to the atmosphere?

• volcanoes
• combustion of fossil fuels
• animal and plant respiration
• all of these

Organisms that need nitrogen to survive.

• only plants

• only animals

• only bacteria

• all living things

How do animals get the carbon and nitrogen they need?

• From the air they breathe

• From the water they drink

• From the food they eat

• From the sun

Plants and animals cannot use nitrogen directly from the air.

• True

• False

According to this diagram, plants use nitrogen to make _________________________

• bacteria

• animals

• proteins

• decomposers

This is released by the weathering of rocks.

• Carbon
• Oxygen
• Phosphorus
• Nitrogen

What is the largest reservoir for nitrogen?

• the ocean

• rocks and minerals

• the atmosphere

• bacteria