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Biology Terms for invertebrates.


no definite shape; cannot be divided into equal parts

radial symmetry

have body parts arranged around a central axis; round

bilateral symmetry

body design in which there are equal right & left halves


sensory organs & nerves located near the front or head region


thin projections of tissue that are rich n blood vessels that allow for gas exchange

closed circulation

heart pumps blood throughout the body through a series of blood vessels

open circulation

heart pumps blood into a body cavity without the use of vessels

hydrostatic skeleton

cavity is filled with water to act as a support system


rigid external skeleton on the outside of an animals body


skeleton composed of a hard material such as bone that helps support an animals body


animal that possesses both male & female reproductive parts

external fertilization

egg & sperm unite outside the female's body

internal fertilization

egg & sperm unite inside the female's body


animal that does not possess a backbone


organism that does not move throughout its life & stays in one place

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