Everything in Earth's system can be placed into one of four major subsystems: land, water, living things, or air. These four subsystems are called “spheres.” These four interconnected parts that make up a complete system, in this case, of life on earth.
The spheres are:
1. Atmosphere
2. Hydrosphere
3. Lithosphere
4. Biosphere.
1. Atmosphere:
- The earth’s atmosphere, a complex fluid system of gases and suspended particles, did not have its origin in the beginning of the planet.
- The atmosphere as of today has been derived from the Earth itself by chemical and biochemical reactions.
- The atmosphere is a mixture of nitrogen (about 78%), oxygen (about 21%), and other gasses (about 1%) such as carbon dioxide (0.039%), argon (0.93%) and the rest are trace gases (krypton, neon, helium, and xenon).
- It extends from less than 1 m below the planet's surface to more than 10,000 km above the planet's surface.
- The atmosphere is divided into several layers and amongst the layers is the stratosphere that contains the ozone layer which protects the organisms in the biosphere from the sun’s harmful radiation.
- Other layers of the atmosphere include the troposphere, mesosphere, thermosphere, and the exosphere.
- The atmosphere is always in constant interaction with the hydrosphere, giving rise to the planets weather conditions.
- The air is in constant motion around the planet and it is normally responsible for some natural events in the planet such as local breeze, winds, tornado, and tropical cyclones.
2. Hydrosphere:
- The hydrosphere includes all the gaseous, liquid, and solid water of the planet earth.
- The hydrosphere stretches all the way from the Earth’s surface downward numerous miles into the lithosphere and high above the crust into the atmosphere.
- Most of the water in the atmosphere is in gaseous form and as it rises higher into the atmosphere it condenses to form clouds which fall back on earth as precipitation.
- A small portion of the water in the hydrosphere is fresh (non-salty).
- More than 97 percent of the earth's water is found in its oceans.
- The remainder is fresh water, two-thirds of which is frozen within the earth's polar regions and mountain snowpacks.
- The glaciers, icebergs, and icecaps are also categorically called the cryosphere.
3. Lithosphere:
- The lithosphere, sometimes called the geosphere, refers to all of the rocks of the earth.
- It includes the planet's mantle and crust, the two outermost layers.
- The actual thickness of the lithosphere varies considerably and can range from roughly 40 km to 280 km.
- In general, the earth crust is composed of three major classes of rocks as classified on the basis of their mode of origin:
- Igneous rocks, sedimentary rocks and metamorphosed rocks.
4. Biosphere:
- The biosphere encompasses all the zones on the Earth in which life is present, i.e., entire bio-resources of the earth.
- These ecological communities interact together with the physical aspects of the earth including the hydrosphere, lithosphere, and the atmosphere.
- The biosphere is made up of biomes, which are areas where plants and animals of a similar nature can be found together.
- Deserts, forests, grasslands, aquatic, tundra, and chaparral are the six main biomes that are present in the biosphere.
- The living things on earth interact with each other in various ways, which is well elaborated under the trophic levels of food chain – how energy is transferred in ecological systems.
