From 1522, when Carlos V delivered a golden terrestrial globe to the navigator Juan Sebastián de Elcano (who had circled the Earth, proving that it is round), the great layers that surrounded the planet received the ending -sphere , in allusion to the spherical shape of the Earth. The terms atmosphere (gaseous part of the Earth), lithosphere (mineral part), hydrosphere (aqueous part) and biosphere (living part of the planet) were created.
What is biosphere
The biosphere (bios = life; sphaîra = sphere, globe) can be defined as the region of the Earth where there is life. The term is also used to refer to the set of regions of the planet that are able to sustain life permanently.
Another way of conceptualizing the biosphere is through the relationship between it and the other components of the Earth, that is, atmosphere , hydrosphere and lithosphere . In fact, every living being has gaseous components of the atmosphere (oxygen and carbon dioxide), water from the hydrosphere and mineral salts (calcium, sodium, sulfur, potassium and phosphorus) from the lithosphere. In the composition of living organisms, the proportion of water is similar to the level present on Earth. Our planet has about 70% water, a value very close to that found in the chemical composition of human beings, for example. This is a demonstration that life is integrated with our planet’s non-living system.
The biosphere extends from the top of the highest mountains (about 8 km in altitude) to the bottom of the oceans (about 11 km in depth). If the Earth were a basketball, the biosphere would be as thick as a layer of paint on that ball.
As the biosphere is very wide, it can be divided by several criteria. One considers only the type of physical environment. Based on this aspect, each subdivision of the biosphere is called a biocycle.
Regarding the physical environment, the biosphere can be subdivided, into terrestrial biocycle (epinocycle), fresh water (limnocycle) and salt water (thalassocycle).
- Thalassocycle: Comprises all marine ecosystems. It occupies, approximately, 70% of the terrestrial surface and presents less diversity of abiotic factors, when compared to terrestrial ecosystems.
- Limnocycle: The limnocycle comprises all freshwater or freshwater ecosystems. It is divided into lentic or calm waters and the lotic or flowing waters.
- Epinocycle: It is the set of mainland ecosystems that is divided into two regions: underground (below ground level – caves and caves) and superficial (terrestrial biomes).
Biocycles, in turn, can be divided into biomes. This term is used by some ecologists to designate a set of ecosystems with similar physiognomic and climatic characteristics. Examples:
- Freshwater biomes: swamps, swamp forests, lakes, rivers and streams;
- Marine biomes: estuaries, straits, mouths of rivers, resurgence regions and coastal waters of the continental shelf;
- Terrestrial biomes: tundra, taiga, temperate and tropical forests, fields and deserts.