biology-dictionary_11-06-2009

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Oils
Flammable substance, usually insoluble in water, and composed chiefly of carbon and
hydrogen. Oils may be solids (fats and waxes) or liquids. Various plants produce vegitable
oils; mineral oils are based on petroleum.
Oligodendrocytes
One of the cells comprising the oligodendroglia.
Oligosaccharides
A carbohydrate that consists of a relatively small number of monosaccharides.
Oligotrophic lake
A nutrient-poor, clear, deep lake with minimum phytoplankton.
Omnivore
A heterotrophic animal that consumes both meat and plant material.
Oncogenes
A gene found in viruses or as part of the normal genome that is involved in triggering
cancerous characteristics.
Ontogeny
The embryonic development of an organism.
Oocyte
A cell that gives rise by meiosis to an ovum.
Oogamy
A condition in which male and female gametes differ, such that a small, flagellated sperm
fertilizes a large, nonmotile egg.
Oogenesis
The process in the ovary that results in the production of female gametes.
Open circulatory system
An arrangement of internal transport in which blood bathes the organs directly and there is
no distinction between blood and interstitial fluid.
Operant conditioning
A type of associative learning that directly affects behavior in a natural context; also called
trial-and-error learning.

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