Phyla Porifera, Cnidaria and Ctenophora

parazoans

(near animals). As sponges lack tissues, organs and definite symmetry they are known as

eumetazoans

(true animals)

colloblasts

Another way ctenophores differ from cnidarians is they lack cnidocytes, instead they have specialized cells known as ____, These cells are found in the epidermis of the tentacles and are used to capture prey. The cells contain a spiral filament with granules on the apical surface. Upon contact with prey, the granules release a strong adhesive material that prevents the prey from escaping.

nematocysts

Cnidocytes contain microscopic structures which are coiled threads that can be discharged like tiny harpoons.

mesoglea

In between these two layers (endoderm and ectoderm) is a jellylike

spicules

Support also comes from a skeleton made up of inorganic and organic

choanocytes

a special cell found inside sponges which are flagellated cells which face the internal cavity, The flagella produce water currents that bring in food particles and oxygen.

three classes of cnidaria

anthozoa, scyphozoa, hydrozoa

Class Hydrozoa

are the hyroids, includes organisms such as hydras and Obelia. The polyp is the predominant body form, but medusa stages are present in their life cycle

Class Scyphozoa

are the jellyfish. The medusa is the predominant body form, but polyp stages are present in their life cycle.

Class Anthozoa

are the sea-anemones and corals. All are of the polyp body form.

sessile organisms

attaching themselves to rocks and other substrates with the sac-like body supported by water

sponges

cells are not considered to be organized into tissues, and these organisms lack nerves and muscles, radial symetry

members of cnidaria

characterized by having 1) a gastrovascular cavity which only has one opening and 2) stinging cells called cnidocytes (figure 3). Cnidocytes contain microscopic structures called nematocysts, which are coiled threads that can be discharged like tiny harpoons. Two body plans are seen in this phylum; the sessile polyp and the free-swimming medusa.

body of a sponge

contains several distinctly different types of cells whose activities are loosely coordinated with one another, multicellular

Cnidaria

do show true tissue organization, they show radial symmetry and are diploblastic, eumetazoans, 10,000

triploblastic

is used to describe animals where the typical three germ layers (endoderm, ectoderm and mesoderm) are found in embryonic development

Diploblastic

means that only two germ layers (endoderm and ectoderm) are produced during embryonic development, from which the animal's tissues and organs will develop

Radial symmetry

means that the animal has a top and bottom, but no head and rear end, and no left and right rides

Porifera

sponges, are among the simplest of all animals,most members completely lack symmetry, 5,000

Ctenophora

structurally more complex than cnidarians, superficially resemble jellyfish, have true muscle cells derived from the mesoderm, are also not strictly radially symmetrical like cnidarians, as they have three main axes of symmetry, none of which produces identical halves

carbonate, silica or organic fibers

the 3 classes of sponges are classified according to whether their spicules are made of

cnidaria body plans

the sessile polyp and the free-swimming medusa.

endoderm

will form an inner layer of digestive tissue known as the gastrodermis

ectoderm

will form the outer epidermis and nerve tissue