U - Zoological Terms

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(L. ulcus, ulcer). An abscess that opens through the skin or a mucous surface.

ultimate cause

(L. ultimatus, last, + causa). The evolutionary factors responsible for the origin, state of being, or purpose of a biological system.


(L. umbilicus, navel). Refers to the navel, or umbilical cord.


(um´bo), pl. umbones (L. boss of a shield). One of the prominences on either side of the hinge region in a bivalve mollusc shell. Also, the "beak" of a brachiopod shell.


(L. ungula, hoof). Hooved. Noun, any hooved mammal.


Methodological assumptions that the laws of chemistry and physics have remained constant throughout the history of the earth, and that past geological events occurred by processes that can be observed today.


(Gr. oueter, ureter). Duct carrying urine from kidney to bladder.


(Gr. ourethra, urethra). The tube from the urinary bladder to the exterior in both sexes.


(Gr. oura, tail, + pous, podos, foot). Posteriormost appendage of many crustaceans.


(L. utriculus, little bag). That part of the inner ear containing the receptors for dynamic body balance; the semicircular canals lead from and to the utricle.

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