A blanket of gases surrounding Earth and consisting of nitrogen (78%), oxygen (21%), argon (0.93%), and other substances that include watervapor, carbon dioxide, ozone, and noble gases such as neon, which together comprise 0.07%.
A combination of all living things on Earth—plants, mammals, birds, reptiles, amphibians, aquatic life, insects, viruses, single-cell organisms, and so on—as well as all formerly living things that have not yet decomposed. Typically, after decomposing, a formerly living organism becomes part of the geosphere.
A system that permits the exchange of energy with its external environment but does not allow matter to pass between the environment and the system. Compare with isolated system, on the one hand, and open system, on the other.
In physics and other sciences, "to conserve" something means "to result in no net loss of" that particular component. It is possible that within a given system, the component may change form or position, but as long as the net value of the component remains the same, it has been conserved.
A form of energy with electric and magnetic components, which travels in waves and, depending on the frequency and energy level, can take the form of long-wave and short-wave radio; microwaves; infrared, visible, and ultraviolet light; x rays; and gamma rays.
In discussing systems, the term environment refers to the surroundings—everything external to and separate from the system.
The return of output to a system, such that the output becomes input that produces further output. Feedback that causes the system to move in adirection opposite to that of the input is negative feedback, whereas positive feedback is that which causes the system to move in the same direction as the input.
The concept, introduced in the 1970s, that Earth behaves much like a living organism, possessing self-regulating mechanisms that preserve life. Sometimes called the Gaian hypothesis, it is named after Gaia, the Greek goddess of the earth.
The upper part of Earth's continental crust, or that portion of the solid earth on which human beings live and which provides them with most of their food and natural resources.
A tendency toward equilibrium.
The quality of beingself-regulating.
The entirety of Earth's water, excluding water vapor in the atmosphere but including all oceans, lakes, streams, groundwater, snow, and ice.
A system that is so fully separated from the rest of the universe that it exchanges neither matter nor energy with its environment. This is an imaginary construct, since full isolation isimpossible.
A system that allowscomplete, or near-complete, exchange of matter and energy with its environment.
A set of principles and procedures for systematic study that includes observation; the formation of hypotheses, theories, and laws; and continual testing and reexamination.
Any set of interactions that can be set apart mentally from the rest of the universe for the purposes of study, observation, and measurement.
A tidal wave produced by an earthquake or volcanic eruption. The term comes from the Japanese words for "harbor" and "wave."
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