EVERYDAY SCIENCE

Detailed explanation-1: -Three classes of Porifera will be discussed as follows: Class: Calcarea that have a skeleton of calcium carbonate spicules and three body forms (Ascon, Sycon and Leucon); Class: Hexactinellida that have 6-rayed spicules of silicon dioxide and a Leucon body type.

Detailed explanation-2: -The phylum Porifera or sponges are mostly aquatic organisms whose body is composed of loosely arranged cells. These cells are of three types – mesenchyme cells, pinacocytes and choanocytes.

Detailed explanation-3: -Classification of Phylum Porifera Their skeleton is composed of calcareous spicules made of calcium carbonate. The body is cylindrical and exhibits radial symmetry. The body organization is asconoid, syconoid, or leuconoid.

Detailed explanation-4: -place in structure of sponges of canals-ascon, sycon, and leucon. The simplest, or ascon, type, found only in certain primitive genera of the Calcarea (e.g., Leucosolenia), is characterized by an arrangement of choanocytes around a central cavity that directly communicates with the osculum.

Detailed explanation-5: -Sycon also called scypha, a genus of marine sponges of the class caldera calcareous sponges is characterized by a fingerlike body shape known as the conoid type of structure.