| Abiotic |
An environmental factor not associated with or derived from living organisms.
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| Absorption |
The taking up and storing of energy, such as radiation, light, or sound, without it being reflected or transmitted.
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| Acceleration |
Rate of change in velocity, usually expressed in meters per second; involves an increase or decrease in speed and/or a change in direction.
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| Acid |
A substance that increases the H+ concentration when added to a water solution.
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| Activation energy |
The least amount of energy required to start a particular chemical reaction.
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| Adaptation |
A characteristic of an organism that increases its chance of survival in its environment.
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| Adenosine triphosphate (ATP) |
An organic compound, C10H16N5O13P3, that is composed of adenosine and three phosphate groups. It serves as a source of energy for many metabolic processes. ATP releases energy when it is broken down into ADP by hydrolysis during cell metabolism.
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| Aerobic |
Occurring in the presence of oxygen or requiring oxygen to live. In aerobic respiration, which is the process used by the cells of most organisms, the production of energy from glucose metabolism requires the presence of oxygen.
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| Aesthetic |
Of or concerning the appreciation of beauty or good taste.
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| Alimentary canal |
The tubular passage that extends from mouth to anus and functions in digestion and absorption of food and elimination of residual waste.
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| Amino acid |
An organic molecule containing an amino group (-NH2) and a carboxyl (-COOH) group from which proteins are synthesized.
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| Amphibian |
A cold-blooded, smooth-skinned vertebrate of the class Amphibia, such as a frog or salamander, that characteristically hatches as an aquatic larva with gills. The larva then transforms into an adult having air-breathing lungs.
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| Anaerobic |
Occurring in the absence of oxygen or not requiring oxygen to live. Anaerobic bacteria produce energy from food molecules without the presence of oxygen.
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| Anatomy |
The scientific study of the shape and structure of organisms and their parts.
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| Angiosperm |
Any of a large group of plants that produce flowers. They develop seeds from ovules contained in ovaries, and the seeds are enclosed by fruits which develop from carpels.
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