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Term Term description

In science, an observation that has been repeatedly confirmed and for all practical purposes is accepted as “true.” Truth in science, however, is never final and what is accepted as a fact today may be modified or even discarded tomorrow.


The term for all of the animal species inhabiting a country, area, or region.



An alternative metabolic pathway that breaks sugars and carbohydrates into acids, gases, or alchohol to produce ATP, which is a molecule used as an energy source in all living cells. Fermentation takes place in the absence of oxygen, and is not as efficient in ATP production as aerobic respiration.

First Law of Thermodynamics

One of the most basic concepts in science, the First Law of Thermodynamics states that the total amount of energy in a system remains constant. Energy may be transferred from one object to another, and energy may convert from one form (say potential energy) to another (say kinetic energy)



A nuclear reaction in which an atomic nucleus, especially a heavy nucleus such as an isotope of uranium, splits into fragments, usually two fragments of comparable mass, releasing from 100 million to several hundred million electron volts of energy; the subdivision of a cell or multi-cellular body into one or more parts and the regeneration of each part into a complete individual.


fissionable uranium

Uranium capable of undergoing fission. Fission is the splitting of one atom into two different atoms, which releases a large amount of energy.


An overflow of water onto lands that are used or usable by man and not normally covered by water. Floods have two essential characteristics: the inundation of land is temporary; and the land is adjacent to and inundated by overflow from a river, stream, lake, or ocean.


A term for all of the plant species found in a country, area, or region.




food web

A group of interrelated food chains in a particular ecological community. A food chain is a sequence of organisms in an ecosystem in which each species is the food of the next member of the chain.


Any herbaceous plant grasses and grass-like forms; non-woody vegetation with succulent leaves and stems.


fossil fuels

Fuels that are formed in the Earth from plant or animal remains; e.g., coal, petroleum, and natural gas.

freshwater ecosystems

Freshwater ecosystems are a subset of Earth's aquatic ecosystems. They include lakes and ponds, rivers, streams, springs, and wetlands. They can be contrasted with marine ecosystems, which have a larger salt content. Freshwater habitats can be classified by different factors, including temperature, light penetration, and vegetation.

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