The Biosphere is the area of the Earth in which living organisms are found. This region extends from the deepest ocean to just a few kilometers into the atmosphere. The Earth is unique in this aspect as it is the only known planet in the solar system in which the conditions are just right to have allowed life to form and evolve.
The Hydrosphere includes all solid (ice on the Earth is often referred to as the Cryosphere), liquid, and gaseous water on the Earth. Earth's surface is composed of 71% water.
The Lithosphere (Geosphere) includes the entire solid surface of the land, 29% of Earth's surface, as well as the various layers of Earth's interior.
The Atmosphere is a gaseous layer surrounding the Earth and it is composed of a mixture of gases including mostly nitrogen (78%), oxygen (21%), carbon dioxide, and water vapour (1%). The greenhouse gases (carbon dioxide, methane, and water vapour) are important as they help to trap the Sun's radiation; without this radiation, the Earth would be too cold for life to exist.
The Anthrosphere has recently been created to describe all of the human created elements (e.g., buildings, roads, cities, etc.) found on the Earth.
These spheres are closely connected in many ways. For example, many birds (biosphere) fly through the air (atmosphere), while water (hydrosphere) often flows through the soil (lithosphere). In fact, the spheres are so closely connected that a change in one sphere often results in a change in one or more of the other spheres. Interactions may occur between spheres; for example, warm water from the ocean evaporates until the atmosphere above cannot hold any more moisture. The wind (atmosphere) moves the moisture (water vapour) over a colder part of the ocean. The atmosphere becomes cold and the water vapour changes to rain. The rain falls on the ocean and some islands in the area get heavy rain too. Spheres may also be affected due to an event, which may occur naturally such as a hurricane, volcanic eruption, or thunderstorm, or they may be caused by humans such as water pollution or climate change.
When analyzing interactions between spheres and events it is important to explain why or how the interactions occur. For example “A decrease in vegetation may have resulted in increased soil erosion because there were fewer roots to hold the soil in place.” In this lithosphere-biosphere interaction it is not simply stated that loss of vegetation resulted in more soil erosion. The statement demonstrates an understanding of the science and the interaction by explaining the reason for the interaction (fewer roots to hold the soil in place).