EVERYDAY SCIENCE

Detailed explanation-1: -All freshwater sponges belong to the class Demospongiae, the most diverse and morphologically complex of the four major groups in the sponge phylum. Within the demosponges, the evolutionary history of the freshwater sponges is long and polyphyletic.

Detailed explanation-2: -They are sponges with a soft body that covers a hard, often massive skeleton made of calcium carbonate, either aragonite or calcite. They are predominantly leuconoid in structure. Their “skeletons” are made of spicules consisting of fibers of the protein spongin, the mineral silica, or both.

Detailed explanation-3: -Unlike other animals, they lack true tissues and organs. Some of them are radially symmetrical, but most are asymmetrical. The shapes of their bodies are adapted for maximal efficiency of water flow through the central cavity, where the water deposits nutrients and then leaves through a hole called the osculum.

Detailed explanation-4: -They range in size from small, encrusting forms, through to large irregular masses. They have spicules (tiny needle-like structures that support the body’s form) of silica dioxide and/or spongin. Demosponges are the sponges most commonly seen whilst diving or walking along the shore.

Detailed explanation-5: -The statement that is true about sponges is c) They lack true tissues. Sponges are very primitive organisms that are made of cells, but their cells are not organized into true tissues. They have an irregular body shape, lacking any type of symmetry, and they are not segmented.