Anabolism
Within a cell or organism, the sum of all biosynthetic reactions (that is, chemical reactions in
which larger molecules are formed from smaller ones).
Anaerobic
Lacking oxygen; referring to an organism, environment, or cellular process that lacks oxygen
and may be poisoned by it.
Anagenesis
A pattern of evolutionary change involving the transformation of an entire population,
sometimes to a state different enough from the ancestral population to justify renaming it
as a separate species; also called phyletic evolution.
Analogy
The similarity of structure between two species that are not closely related; attributable to
convergent evolution.
Analogous
Applied to structures similar in function but different in evolutionary origin, such as the wing
of a bird and the wing of an insect.
Anaphase
The third stage of mitosis, beginning when the centromeres of duplicated chromosomes
divide and sister chromotids separate from each other, and ending when a complete set of
daughter chromosomes are located at each of the two poles of the cell.
Anatomy
The morphological structure of a plant or an animal or of any of its parts.
Androecium
The male reproductive organs of a flower considered as a group; the stamens. Compare
gynoecium.
Androgen
The principal male steroid hormones, such as testosterone, which stimulate the
development and maintenance of the male reproductive system and secondary sex
characteristics.
Aneuploidy
A chromosomal aberration in which certain chromosomes are present in extra copies or are
deficient in number.
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