Oxygen Cycle

What percentage of the Earth's atmosphere is composed of oxygen?

• 78 %

• 21 %

• 10 %

• 5 %

Which process releases oxygen back into the atmosphere during the oxygen cycle?

• Respiration

• Decomposition

• Combustion

• Denitrification

Tags

NGSS.MS-LS1-6

Which organism(s) contribute(s) to the oxygen cycle by performing photosynthesis?

• Animals

• Bacteria

• Plants and algae

• Fungi

Tags

NGSS.MS-LS1-6

Which activity contributes to an imbalance in the oxygen cycle by increasing carbon dioxide levels in the atmosphere?

• Decreasing nitrogen fixation

• Deforestation

• Increasing nitrogen fixation

• Burning fossil fuels

Tags

NGSS.MS-LS1-6

What is the role of decomposers in the oxygen cycle?

• They convert nitrogen into a usable form for plants.

• They release oxygen during photosynthesis.

• They release oxygen during respiration.

• They break down dead organic matter, releasing oxygen.

What is the primary source of oxygen released during photosynthesis?

• Nitrogen (N2)

• Ozone (O3)

• Carbon dioxide (CO2)

• Water (H2O)

Tags

NGSS.MS-LS1-6

During photosynthesis, plants take in ________ and release ________.

a) Oxygen, carbon dioxide

b) Carbon dioxide, oxygen

c) Nitrogen, oxygen

d) Water vapor, carbon dioxide

• Oxygen, carbon dioxide

• Carbon dioxide, oxygen

• Carbon dioxide, oxygen

• Water vapor, carbon dioxide

Tags

NGSS.MS-LS1-6

NGSS.MS-LS2-3

What happens to the oxygen released by plants during photosynthesis?

• It remains in the atmosphere indefinitely.

• It combines with carbon dioxide to form carbohydrates.

• It combines with carbon dioxide to form carbohydrates.

• It gets converted into water vapor through evaporation.

Tags

NGSS.MS-LS1-6

How does deforestation affect the oxygen cycle?

• It increases oxygen levels in the atmosphere.

• It decreases oxygen levels in the atmosphere.

• It has no impact on the oxygen cycle.

• It leads to an imbalance in the carbon dioxide-oxygen ratio.

Tags

NGSS.MS-LS1-6

NGSS.MS-LS2-3

What role do animals play in the oxygen cycle?

• They release oxygen during respiration.

• They absorb carbon dioxide and release oxygen

• They contribute to the decomposition of dead organic matter.

• They convert atmospheric nitrogen into usable forms.