carbon cycle

When humans burn fossil fuels, most of the carbon quickly enters the                       as carbon dioxide.

• Water
• Atmosphere
• Sun
• Air

Which one of these does not add CO2 to the atmosphere?

• cooking with gas
• planting trees
• burning wood
• riding in a bus

What does not produce carbon dioxide?

• Photosynthesis
• Burning Fossil Fuels
• Animal respiration
• Plants decaying

How do living organisms return carbon to the atmosphere in the carbon cycle?

• respiration and photosynthesis
•  decomposition and respiration

In the carbon cycle, producers take in the gas __

• carbon dioxide
• oxygen
• nitrogen
• carbon monoxide

oxygen is a gas produced by _ and used by  _ 

• plants and animals 
• photosynthesis and carbon dioxide 
• animals and plants 
• carbon dioxide and photosynthesis

All of the carbon in existence is continually recycled in the carbon cycle

• True
• False

Which of the following removes carbon from the atmosphere?

• Combustion
• Respiration
• Photosynthesis
• Death

Organisms that do not decompose can be buried and become what?

• water
• nutrients
• air
• fossil fuels

If the plant population decreased, the amount of carbon would _________.

• Stay the same
• Increase
• Decrease