The Oxygen and Carbon Dioxide Balance: Concept Map

Concept Map

Organise the vocabulary, quantities and relationships into a connected model.

This extension applies that lens specifically to The Oxygen and Carbon Dioxide Balance.

Photosynthesis and respiration are opposites, and together they keep the gases of the atmosphere in balance.

In daylight a healthy plant photosynthesises much faster than it respires, so overall it takes in carbon dioxide and gives out oxygen. At night only respiration continues, so the plant takes in oxygen and gives out carbon dioxide, just like you do.

This is what interdependence means: animals depend on plants for oxygen and food; plants depend on the carbon dioxide that animals (and decay, and fires) return to the air.

Worked example. A sealed glass jar holds a healthy pot plant and a small grasshopper.

• Left on a sunny windowsill: the plant photosynthesises, releasing oxygen for the grasshopper; the grasshopper respires, releasing carbon dioxide for the plant. Both can survive for a long time.
• Locked in a dark cupboard: photosynthesis stops. Now both organisms are respiring and neither is making oxygen. The oxygen runs out and the carbon dioxide builds up.

The jar makes visible what the whole atmosphere is doing all the time.