Sponges
Sponges have a relatively simple, porous body. Members of the phylum Porifera have no true tissues. Their flagellated choanocytes filter food from water passing through pores in the body.
Sponges are sessile, mostly marines suspension feeders, with saclike bodies consisting of two layers of cells. They are the simplest animals, with no nerves or muscles.
Cnidarians
Cnidarians are radial animals with tentacles and stinging cells. Members of the phylum Cnidaria have true tissues and a gastrovascular cavity. Their two body forms are polyps such as hydras and medusae (jellies). Cnidarians are radial animals such as anemones, corals, and jellies, with tentacles bearing stinging cells. Their prey are digested in a gastrovascular cavity.
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FlatwormsFlatworms are the simplest bilateral animals, with three tissue layers, organs, and systems. Free-living flatworms suck food into a gastrovascular cavity. Members of the Phylum Platyhelminthes are bilateral animals with no body cavity. a planarian has a gastrovascular cavity and a simple nervous system. Flukes and tapeworms are parasitic flatworms with complex life cycle. |  |
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 | NematodesNematodes are tubular worms with a pseudocoelm and a complete digestive tract. Many live in soil and water, and some are parasitic of plants and animals. Members of the Phylum Nematoda are covered by a protective cuticle. Many nematodes (roundworms) are free-living decomposers; others are plant or animal parasites.  |
MolluscsMolluscs are diverse because of variation on a common body plan. Members of the phylum Mollusca include gastropods (snails and slugs), bivalves (clams), and cephalopods (octopuses and squids). All molluscs have a muscular foot, with a visceral mass, a coelom, and a membranous mantle that usually secretes a shell. Molluscs have a circulatory systems, and most have gills. Many molluscs feed with a rasping radula.  | .jpg)   |
.jpg.opt404x313o0,0s404x313.jpg) | ArthropodsArthropods are segmented animals with jointed appendages and exoskeleton. Segments can be fused and appendages adapted for various functions. All have open circulatory systems. Most crustaceans are aquatic. The four lineages of the Phylum Arthropoda are chelicerates (arachnids such as spiders), the lineage of millipedes and centipedes, the aquatic crustaceans (lobsters and crabs), and the terrestrial insects. |
  | EchinodermsEchinoderms, such as sea stars and sea urchins, have spiny skin, an endoskeleton, and a water vascular system with tube feet for movement. Members of the phylum Echinodermata are radially symmetric as adults. These unique marine creatures are the closest relative of chordates.  |
Annelids
Annelids are segmented worms (earthworms, leeches, and marine polychaetes). Their segmented bodies and coeloms allow for flexibility and mobility. Annelids have closed circulatory systems, and exchange gases via gills or the body surface. Members of the Phylum Annelida include earthworms, polychaetes, and leeches.
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Insects
Insects are the most successful groups of animals. Their development often includes metamorphosis. Insects have a three-part body (which are the head, thorax, and the abdomen) and three pairs of legs; most have wings. specialized appendages and protective color patterns, which frequently result from evolutionary changes in the timing and location of homeotic gene expression, have played a major role in this group's success.
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 | ChordataThe phylum Chordata is distinguished by four features. Chordates have a dorsal, hollow nerve cord, a stiff longitudinal notochord, phyryngeal slits, and a muscular post-anal tail. The simplest chordates are tunicates and lancelets, marine invertebrates that use their phyrngeal slits for suspension feeding.  |
