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.

Verified step by step guidance

1. Identify the key characteristics of sponges: Sponges, belonging to the phylum Porifera, are simple animals that lack true tissues and organs. They have a porous body with cells that can transform and perform different functions.
2. Understand the concept of tissues: Tissues are groups of similar cells that work together to perform a specific function. Most animal phyla have organized tissues, which can form organs.
3. Compare sponges with other phyla: Other animal phyla, unlike sponges, typically have organized tissues. These tissues contribute to more complex structures and functions within the organisms.
4. Review the other options: a) A body cavity is not unique to distinguishing sponges as some other invertebrates also lack a body cavity. b) A complete digestive tract is absent in sponges, but this is not the primary distinguishing feature. c) Mesoderm, the middle layer of cells, is absent in sponges, but the absence of tissues is more fundamental.
5. Conclude the primary distinction: The primary distinction between sponges and other animal phyla is based on the absence of tissues in sponges, making option 'd' the correct answer.

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.