Phylum Coelenterata: [Coel-Hollow/Cavity, Enteron-Gut/Intestine]

• This phylum is also known as Cnidaria.
• Habitat: They are aquatic animals, found in both fresh and marine water.
• Habit: some of them live in colonies while others lead a solitary life.
• Symmetry: Their body shows radial symmetry.
• Body cavity: They are acoelomate, i.e., true cavity is absent. But a hollow cavity is present in a gut region or the region of intestine which is known as gastrovascular cavity or coelenteron with a single opening for ingestion and egestion.
• Body differentiation: They are multicellular which possess tissue level of organization with distinct division of labour. Thus they are complex than the poriferans.
• Germ layer: They are diploblastic as body develops from two layers of cells. Outer layer- ectoderm or epidermis makes the body wall and the inner layer- endoderm or gastrodermis forms the inner lining of body. Two layers are glued together through a gelatinous layer known as mesoglea.

Body organization:

• They have tentacles that bear stinging cells called nematocyst. These cells help in paralyzing the prey.
• Skeleton:  Some of them [corals] have the exoskeleton made up of lime.
• Life processes: Digestive, respiratory and excretory organs are absent.
• Reproduction is usually asexual [budding] or some of them show sexual reproduction.
• Nervous system is primitive comprised of network of nerve cells.

Examples:

• Hydra, corals, sea anemone etc.

Comparison of porifera and coelenterate: