Material cycles: the water cycle | Starter Quiz | Oak National Academy

Which of the following organisms are decomposers?

• earthworm

• leopard

• butterfly

• bat

• dung beetle

Answer explanation

Earthworms and dung beetles are examples of decomposers. Earthworms break down leaves and plant material. Dung beetles use animal waste (dung) as a source of food for their larvae.

Carbon dioxide is an important part of which of the following cycles?

• water cycle

• nutrient cycle

• life cycle

• carbon cycle

Answer explanation

Carbon dioxide forms an important part of how carbon is cycled in the carbon cycle.

How is carbon returned to the atmosphere in the carbon cycle?

• combustion

• respiration

• photosynthesis

• decomposition

Answer explanation

When fossil fuels are burned (a process called combustion), carbon dioxide is released back into the atmosphere. Plants and animals use some of their food for cellular respiration. Respiration releases carbon dioxide to the air.

Plants take in carbon dioxide from the air. They use this for ___.

Answer explanation

Plants take in carbon dioxide from the air. They use this for photosynthesis to make their own food.

Why are decomposers important in a stable ecosystem?

• They return nutrients to the atmosphere.

• They break down dead organisms and waste material.

• They cause organisms to die.

Answer explanation

Decomposers break down dead bodies and waste material. They keep the ecosystem clean and healthy by decomposing dead and decaying organic matter.

Which of the following statements about the amount of carbon dioxide in the atmosphere is correct?

• The carbon dioxide levels are decreasing as plants are photosynthesising more.

• The carbon dioxide levels are increasing as we are burning more fossil fuels.

• The carbon dioxide levels are increasing as all organisms are respiring less.

• The carbon dioxide levels are increasing due to deforestation.

• The carbon dioxide levels are decreasing as the oceans absorb it all.

Answer explanation

The carbon dioxide levels are increasing as we are burning more fossil fuels and carrying out deforestation.