Species-specific
Characteristic of a particular species.
Specific
Unique; for example, the proteins in a given organism, the enzyme catalyzing a given
reaction, or the antibody to a given antigen.
Specific heat
The amount of heat that must be absorbed or lost for 1 g of a substance to change its
temperature 1°C.
Spectrophotometer
An instrument that measures the proportions of light of different wavelengths absorbed and
transmitted by a pigment solution.
Sperm
A male gamete.
Spermatid
Each of four haploid cells resulting from the meiotic divisions of a spermatocyte; each
spermatid becomes differentiated into a sperm cell.
Spermatocytes
The diploid (2n) cells formed by the enlargement and differentiation of the spermatogonia;
they give rise by meiotic division to the spermatids.
Spermatogonia
The unspecialized diploid (2 n) cells on the walls of the seminiferous tubules that, by
enlargement, differentiation, and meiotic division, become spermatocytes, then spermatids,
then sperm cells.
Spermatogenesis
The continuous and prolific production of mature sperm cells in the testis.
S phase
The phase of the mitotic cycle during which DNA synthesis occurs.
Sphenodon
Either of two nocturnal lizardlike reptiles (Sphenodon punctatus or S. guntheri) that are
found only on certain islands off New Zealand and are the only extant members of the
Rhynchocephalia, an order that flourished during the Mesozoic Era. Also called sphenodon.
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