Identify the common characteristics of phylum Cnidaria

Cnidarians represent a more complex level of organization than Porifera. They possess outer and inner tissue layers that sandwich a noncellular mesoglea. Cnidarians possess a well-formed digestive system and carry out extracellular digestion. The cnidocyte is a specialized cell for delivering toxins to prey as well as warning off predators. Cnidarians have separate sexes and have a lifecycle that involves morphologically distinct forms. These animals also show two distinct morphological forms—medusoid and polypoid—at various stages in their lifecycle.

What You’ll Learn to Do

• Identify common structural and organization characteristics of the phylum Cnidaria
• Identify the features of animals classified in class Anthozoa
• Identify the features of animals classified in class Scyphozoa
• Identify the features of animals classified in class Cubozoa
• Identify the features of animals classified in class Hydrozoa

Learning Activities

The learning activities for this section include the following:

• Characteristics of Phylum Cnidaria
• Classes in the Phylum Cnidaria
• Self Check: Phylum Cnidaria