The System and Structure of the Earth

9.1  The System and Structure of the Earth
The Earth system consists of four main components which are interconnected, namely atmosphere, biosphere, hydrosphere and geosphere:


Air zone covering the Earth’s surface.


Life zone consists of a variety of life such as humans, animals, plants and microorganisms


Water zone that includesrivers, lakes, seas and also water trapped as ice, underground waterand water vapour in the atmosphere.


Rock and soil zone on the Earth’s surface.


Atmospheric Stratification

Earth’s atmosphere consists of five layers:



  • 480 km and above
  • Contains light gases such as helium and hydrogen.
  • Air becomes thinner towards space. 
  • Communication satellites orbiting Earth in this layer allow phone calls and television broadcasts.


  • 80 - 480 km 
  • Also known as the ionosphere because it contains ions that can reflect radio waves.
  • Aurora, a stream of colourful lights resulting from reactions of charged particles with Earth’s magnetic field and atmospheric gases occurs here


  • 50 - 80 km
  • Burning and destruction of meteorites occur in this layer.


  • 13 - 50 km
  • This layer is suitable and stable for aircraft flights.
  • The ozone layer that contains ozone gas which absorb harmful ultraviolet rays from sunlight is found here.
  • The ozone layer depletes when chlorofluorocarbons (CFCs) released from pesticides, refrigerators and air-conditioners break down ozone molecules in the ozone layer.


  • 0 - 13 km
  • The layer where living organism breathes, wind blows and where clouds, rain and snow form.

Example of question:

What do you feel when you climbing a mountain?

Explain your answer.


The weather is cold and have difficulties in breathing.

It is because from troposphere to stratosphere, the altitude increases.

The higher the altitude, the lower the air pressure.


Ocean Stratification



The water is very shallow and light can penetrate.

This makes the zone suitable as a habitat for plants.



This zone has little or no light.

It is difficult for plants to live at this depth but this level of depth becomes the habitat for large marine animals, such as giant squids and various species of whales.


This zone is very deep and no light can reach it.

Therefore, most animals in this zone have shimmering bodies or are able to glow in the dark.

Earth's Layer

Source: Textbook Science Form 3

Earth is the Only Home for Living Organisms

Characteristics of Earth that makes it suitable for all life:

  • Temperature - Not too hot or too cold
  • Presence of water and oxygen