The four main systems of the
Earth are the rocks, water, air and life. Mountains, volcanoes, hills, plateaus,
sand, pebbles represent the rocks. These are where most of the plants and vegetation
takes place. Also, these are where most of the organisms that lives on land take
place. Oceans, rivers, ponds, lakes, waterfalls represent the water. These are
where most of the organisms that lives on water is located. It is said that earth
consists of 70% of water and the rest are land. Air is the reason why all of
the microorganisms living on earth are alive because of its composition, 21%
oxygen and 79% nitrogen. And life, the organisms that dwells on earth.
