biology-dictionary_11-06-2009

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Adaptation
The evolution of features that make a group of organisms better suited to live and
reproduce in their environment.
Adaptive peak
An equilibrium state in a population when the gene pool has allele frequencies that
maximize the average fitness of a population's members.
Adaptive radiation
The emergence of numerous species from a common ancestor introduced into an
environment, presenting a diversity of new opportunities and problems.
Adenosine diphosphate
A nucleotide consisting of adenine, ribose, and two phosphate groups; formed by the
removal of one phosphate from an ATP molecule.
Adenosine monophosphate
A nucleotide consisting of adenine, ribose, and one phosphate group; can be formed by the
removal of two phosphates from an ATP molecule; in its cyclic form, functions as a "second
messenger" for a number of vertebrate hormones and neurotransmitters.
Adenosine triphosphate
An adenine-containing nucleoside triphosphate that releases free energy when its
phosphate bonds are hydrolyzed. This energy is used to drive endergonic reactions in cells.
Adenylyl cyclase
An enzyme that converts ATP to cyclic AMP in response to a chemical signal.
ADH
Abbreviation of antidiuretic hormone.
Adhesion
The tendency of different kinds of molecules to stick together.
ADP
Abbreviation of adenosine diphosphate.
Adaxial
In botany terminology adaxial describes a side or surface nearest or facing toward the axis
of an organ or organism, such as the upper surface of a leaf lamina

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