Practice question

Porifera notably lack true tissues defined as coherent cell sheets sharing basal lamina composed of type IV collagen, tight junctions and coordinated physiological function. Sponge cells show loose aggregation, high totipotency, archaeocytes can differentiate into choanocytes, pinacocytes or sclerocytes as needed, dissociated cells reaggregate forming new sponge indicating reversible differentiation. Canal system, skeleton of spongin fibers and siliceous or calcareous spicules present, collagenous mesohyl exists but not organized true epithelium. Thus tissue grade absent remaining cellular grade among metazoa. This concept holds high importance for NEET, CBSE board, CUET and competitive examinations focusing on comparative