6.1 Introduction to the atmosphere

Significant ideas

• The atmosphere is a dynamic system that is essential to life on Earth.

• The behaviour, structure and composition of the atmosphere influence variations in all ecosystems.

Knowledge and understanding

1. The atmosphere is a dynamic system (with inputs, outputs, flows and storages) that has undergone changes throughout geological time.

2. The atmosphere is a predominantly a mixture of nitrogen and oxygen, with smaller amounts of carbon dioxide, argon, water vapour and other trace gases.

3. Human activities impact atmospheric composition through altering inputs and outputs of the system. Changes in the concentrations of atmospheric gases—such as ozone, carbon dioxide, and water vapour—have significant effects on ecosystems.

4. Most reactions connected to living systems occur in the inner layers of the atmosphere, which are the troposphere (0–10 km above sea level) and the stratosphere (10–50 km above sea level).

5. Most clouds form in the troposphere and play an important role in the albedo effect of the planet.

6. The greenhouse effect of the atmosphere is a natural and necessary phenomenon maintaining suitable temperatures for living systems.