Understanding the Carbon Cycle

What is the primary cause of global warming according to the passage?

• Decrease in atmospheric oxygen

• Spiking atmospheric CO2 concentrations

• Increase in nitrogen levels

• Reduction in methane levels

Which of the following gases was NOT mentioned as part of the early Earth's atmosphere?

• Ammonia

• Methane

• Oxygen

• Nitrogen

What process do plants use to convert carbon dioxide into oxygen?

• Respiration

• Photosynthesis

• Combustion

• Fermentation

What is the role of greenhouse gases in Earth's atmosphere?

• They cool down the Earth's surface

• They absorb heat energy, increasing Earth's temperature

• They block sunlight from reaching Earth

• They convert oxygen into carbon dioxide

What makes Earth "earthy" and unique among planets, according to the passage?

• The presence of water

• The carbon cycle

• The abundance of oxygen

• The presence of life

What significant change did plants bring to Earth's atmosphere?

• They increased the levels of methane

• They decreased the levels of nitrogen

• They produced huge amounts of oxygen

• They increased the levels of ammonia

What was the effect of the changes in Earth's atmosphere due to plant activity?

• It trapped more heat in the atmosphere

• It allowed more heat to radiate back into space

• It increased the levels of carbon dioxide

• It decreased the levels of oxygen

Which of the following is a greenhouse gas mentioned in the passage?

• Oxygen

• Nitrogen

• Carbon Dioxide

• Helium

What was the state of free oxygen in the early Earth's atmosphere?

• It was abundant

• It was scarce

• It was the primary component

• It was non-existent

What did plants use carbon dioxide for, according to the passage?

• To produce methane

• To create life

• To increase atmospheric pressure

• To generate heat