biology-dictionary_11-06-2009

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Polyphyletic
Pertaining to a taxon whose members were derived from two or more ancestral forms not
common to all members.
Polyploid
Cell with more than two complete sets of chromosomes per nucleus.
Polyploidy
A chromosomal alteration in which the organism possesses more than two complete
chromosome sets.
Polyribosome
An aggregation of several ribosomes attached to one messenger RNA molecule.
Polysaccharide
A polymer of up to over a thousand monosaccharides, formed by condensation synthesis.
Polysomes
A cluster of ribosomes connected by a strand of messenger RNA and actively synthesizing
protein. Also called polysome.
Polynsaturated fats
Relating to an organic compound, especially a fat, in which more than one pair of carbon
atoms are joined by double or triple bonds
Pores
A minute opening in tissue, as in the skin of an animal, serving as an outlet for perspiration,
or in a plant leaf or stem, serving as a means of absorption and transpiration.
Population
A group of individuals of one species that live in a particular geographic area.
Population bottleneck
Type of genetic drift that occurs as the result of a population being drastically reduced in
numbers by an event having little to do with the usual forces of natural selection.
Population density
The number of individuals of a population per unit area or volume of living space.
Population viability analysis (PVA)
A method of predicting whether or not a species will persist in a particular environment.

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