The distinction between sponges and other animal phyla is based mainly on the absence versus the presence of a. a body cavity. b. a complete digestive tract. c. mesoderm. d. tissues.

Key Concepts

Tissue Organization

Tissue organization refers to the arrangement of cells into specialized groups that perform specific functions. In animals, this organization is crucial for the development of complex structures and systems. Sponges, classified as Porifera, lack true tissues, which distinguishes them from other animal phyla that exhibit organized tissue structures, such as epithelial, connective, muscle, and nervous tissues.

Body Cavity (Coelom)

A body cavity, or coelom, is a fluid-filled space within the body that provides a protective cushion for internal organs and allows for their movement and growth. Animals can be classified based on the presence or absence of a coelom: coelomates have a true coelom, while acoelomates, like sponges, do not possess this feature. This distinction is significant in understanding the evolutionary relationships among different animal groups.

Digestive Tract

A complete digestive tract is a system that allows for the ingestion, digestion, and absorption of food through a continuous tube running from mouth to anus. In contrast, sponges lack a digestive tract; they filter feed by drawing water through their porous bodies and extracting nutrients directly from the water. This fundamental difference in feeding mechanisms highlights the evolutionary adaptations of various animal phyla.