We are not yet aware of the existence of any other place in the universe than Earth, where the phenomenon we call life happens.

Life on earth is possible because sunlight comes here. Thanks to its position in relation to the sun, our planet receives an amount of solar energy that allows the existence of water in liquid state, and not only in solid state (ice) or gas (vapor).

Water is essential to living organisms. The presence of water enables the life of plants and other beings capable of producing food from solar energy and also indirectly allows the survival of all other living beings that feed on plants or animals. By photosynthesis that there is the absorption of water and carbon dioxide and release of oxygen, the energy of the sun is transformed into a type of energy present in sugars, which can then be harnessed by beings who perform this process and by other beings related to them. Search for food.

The earth can be divided like this:

  • Lithosphere - the solid part formed from the rocks;
  • Hydrosphere - the total body of water on the planet (its rivers, lakes, oceans);
  • Atmosphere - the air layer surrounding the planet;
  • Biosphere - the inhabited regions of the planet.

Biosphere is the set of all Earth's ecosystems. It is a concept of ecology, related to the concepts of lithosphere, hydrosphere and atmosphere. The biosphere includes all living organisms living on the planet, although the concept is generally extended to include their habitats as well.

The biosphere includes all ecosystems that are present from the high mountains (up to 10,000 m in height) to the seabed (up to about 10,000 m deep).

In these different locations, environmental conditions also vary. Thus, natural selection acts in a diversified way on living beings in each region. Under great depths in the sea, for example, only beings adapted to the great pressure that water exerts on them and the low (or absent) luminosity survive. Already in the high mountain altitudes, beings survive adapted to low temperatures and thin air.

In the biosphere, therefore, air, water, soil, light are factors directly related to life.