Answer to Question #223430 in Zoology for Debbie

Question

Examine the distinguishing features of cnidarians, porifera, and their subdivisions, and write 

the classification, with reasons, for each specimen on the drawing.

Answer 1

Distinguishing features of cnidarians and porifera.

1. Cnidarians show the presence of choanocytes or collar cells. Porifera show the presence of cnidoblasts or nematocytes.

2. In cnidarians,animals are asymmetrical. In porifera,animals are radially symmetrical.

3. In cnidarians,water canal system is well-developed. In porifera,water canal system is absent.

Subdivisions of cnidarians and porifera

The phylum Porifera is divided into four classes. The Calcarea are sponges with a calcareous skeleton. The Hexactinellida are syncytial glass sponges, whose skeleton consists of silicone dioxide. The Demospongiae are common sponges, and the Homoscleromorpha comprises sponge species possessing a basement membrane and metazoan-like cell junctions. 

Cnidaria are classified into two main assemblages: Anthozoa (Hexacorallia and Octocorallia) are cnidarians with a reproductive polyp and the absence of a medusa stage. Medusozoa (Cubozoa, Hydrozoa, Scyphozoa, Staurozoa) are cnidarians that usually possess a reproductive medusa stage.