A type of animal that does not have a backbone: "Invertebrates are extraordinarily varied; many are microscopic, but the largest are over 33 feet (10 meters) long."

"There is no such thing as a typical invertebrate, and many of the phyla have very little in common with each other."

"The most simple invertebrates do not have heads or brains, and they usually depend on internal fluid pressure to keep their shapes."

"Those invertebrates at the opposite end of the 'simple' species have well-developed nervous systems, as well as, elaborate sense organs, including complex eyes and they also have external body cases, or exoskeletons, with legs that bend by means of flexible joints; however, they never have internal skeletons made of bone."

1. A reference to animals that do not have a backbone: There are groups of animals with vertebrae, or backbones consisting of small bones fitted together like little beads on a string; and then there are many creatures of different shapes and sizes that do not have backbones, and they are classified as invertebrate animals.

Some invertebrate species include moths, butterflies, spiders, crayfish, and snails; all of which do not have internal skeletons to support their bodies.

2. Descriptive of those who are "spineless" and who cannot make difficult decisions or they do not have the courage or determinations necessary to fulfill the tasks: There are too many invertebrate people who don't have the "backbones" necessary to overcome difficulties and to achieve success even with important objectives. © ALL rights are reserved.

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The branch of zoology concerned with the taxonomy, behavior, and morphology of invertebrate animals or any animal lacking a backbone and an internal skeleton, including all species not classified as vertebrates