Ecosystems

Which of these correctly describes the relationship between plants and animals in the carbon dioxide-oxygen cycle?

• Plants produce and release the oxygen that animals need to breathe.

• Plants produce and release the carbon dioxide that animals need to breathe.

• Animals produce and release the oxygen that plants need to make their own food.

• Animals produce and release the oxygen that plants convert to carbon dioxide.

What would most likely happen to the carbon dioxide-oxygen cycle if Earth's large forests were all cut down?

• There would be more carbon dioxide in the atmosphere because fewer plants would be using it to produce their own food.

• The remaining plants would stop producing carbon dioxide, and animals would use less oxygen.

• The remaining plants would produce more oxygen, and animals would produce less carbon dioxide.

• There would be more oxygen in the atmosphere because fewer plants would be using it to produce their own food.

Which statement best describes the relationship between humans and plants in the carbon dioxide-oxygen cycle?

• Humans depend on oxygen released into the air by plants, and plants depend on carbon dioxide that humans release into the air.

• Plants produce carbon dioxide as a product of photosynthesis and release it into the air to provide energy for humans.

• Plants depend primarily on energy supplied by oxygen for photosynthesis, a process which releases carbon dioxide needed by humans.

• Humans and plants use gases in the air and the energy of sunlight to produce their own food.

Animals and plants use substances that cycle through the environment. Which substance is needed by plants to survive and is released into the environment by animals?

• Oxygen

• Sugar

• Salt

• Carbon dioxide

Many types of plants grow in a forest ecosystem. How do plants affect the air that forest animals breathe?

• Plants use oxygen from the air to make food.

• Plants release pollution into the air.

• Plants release energy from the sun into the air.

• Plants take in carbon dioxide and release oxygen into the air.

________________ could increase the amount of oxygen in the air.

• Building more houses

• Burning more oil

• Paving more streets

• Planting more trees

Plants use _____________ to make their own food during photosynthesis.

• water
• energy from the Sun
• CO2
• water, energy from Sun, CO2

What is the process where animals and people use oxygen to make carbon dioxide?

• Photosynthesis

• Respiration

Do plants need people?

• No

• Yes

Which answer best defines photosynthesis?

• the movement of carbon dioxide and oxygen between organisms and the air
• Tiny holes in the leaves of a plant that allow gases to enter or leave the plant
• the process in which plants use energy from the sun to make their own food
• a gas in the atmosphere that plants use to make food