EVERYDAY SCIENCE

Detailed explanation-1: -Sponges have cellular-level organization, meaning that that their cells are specialized so that different cells perform different functions, but similar cells are not organized into tissues and bodies are a sort of loose aggregation of different kinds of cells.

Detailed explanation-2: -Sponges are the only animals that lack true tissues. They only possess the cellular level of organization. Remember the levels of organization that make up the body of living organisms (cells-tissues-organs-organ systems-organism) from Biology I.

Detailed explanation-3: -A sponge’s body is hollow and is held in shape by the mesohyl, a jelly-like substance made mainly of collagen and reinforced by a dense network of fibers also made of collagen. The inner surface is covered with choanocytes, cells with cylindrical or conical collars surrounding one flagellum per choanocyte.

Detailed explanation-4: -As mentioned above, sponges are diploblasts and consist of essentially two cell layers. Between these two layers there is a gelatinous substance called the mesohyl.