Poriferans vs Cnidarians
Why are sponges considered less complex than cnidarians?
Sponges are basically just a collection of cells living together. They
have no real tissues. Cnidarians have simple tissues. Neither have a gut.
Sponges are multicellular, but do have a very simple grade of organization.
The body is made up of loosely connected cells which are embedded in a
gelatinous matrix. Sponges lack real organs or true tissues.
Cnidarians have two true tissue layers (an outer epidermis and an inner
gastrodermis) separated by a connective tissue layer called the mesoglea.The
nervous system of cnidarians consists of a diffuse network of neurons called
a nerve net in which any direction of conduction is possible.
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Update: June 2012