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Toxin

any substance harmful to living cells

Trophic

pertaining to growth or nutrition

Tube feet

extension of the water vascular system of echinoderms (sea stars, sea urchins, etc.) that aids in locomotion, grasping and feeding

Tundra

treeless, level or rolling ground above the timberline of spruces and firs in polar regions (Arctic tundra) or on high mountains (alpine tundra), characterized by bare ground and rock or by such vegetation as mosses, lichens, small herbs, and low shrubs.

Turbid

stirred up sediment; cloudy

Turf

thick mat of plants and animals on a substrate

Undulate

to move back and forth in a wave-like motion

Unicellular

single-celled

Upwelling

deep, cold, nutrient-rich waters that rise to the surface from deeper areas of the ocean

Urticating hair

barbed hairs that cover the dorsal and posterior surface of a tarantula's abdomen

Vascular plants

plants that have vessels to conduct and circulate fluids around their parts

Vasculated

having numerous blood vessels

Velum

shelf or rim that projects inward around the margin of the bell of a hydozoan, partially closing the opening

Venom

a toxin injected into a victim

Ventral

toward the lower side or belly; underside; opposite of the dorsal side

Vertebrate

animal with a backbone: having a dorsal column of vertebrae

Vertical migration

periodic movement of an animal up and down the ocean's water column

Vertical zonation

distinct banding of groups, populations or organisms at different levels of a habitat

Vestigial

usually a non-functioning remnant of a body part that once existed as a fully functioning part of an organism

Vibrissa

whisker(s) of mammals, plural: vibrissae

Viviparous

producing living young that develop from eggs retained within the mother's body, receiving nourishment through the placenta

Warm-blooded

body temperature is controlled internally and is maintained at a constant level; endothermic

Water column

vertical depth of water; area between the surface of the ocean and the ocean floor

Water vascular system

system of fluid-filled canals and structures that aid in locomotion and food gathering

Wetlands

biologically productive areas b ordering estuaries, salt marshes and swamps that are occasionally flooded by tidal or river

Whorl

single turn of a spiral shell of a mollusk. A body whorl is the msot recently formed turn of a spiral shell terminating in an aperture.

Wild salmon

salmon that have spent their entire life cycle in the wild and originating from parents that were also produced by natural spawning and continuously lived in the wild

Wrack

any marine vegetation cast up on the shore by wave action, example, kelp

Zero tide

average of the lower low tides

Zonation

distribution of the plants and animals in a community into recognizable, distinctive zones

Zooanthellae

photosynthetic microorganisms that live symbiotically in the tissues of organisms such as corals and jellies

Zooplankton

planktonic animals suspended in the water column

Zygote

fertilized egg