Chapter 33, Problem 33.1CR

Lacking tissues and organs, how do soonges accomplish tasks such as gas exchange, nutrient transport, and waste disposa I?

Summary Introduction

To determine: How sponges perform “gas exchange, nutrient transport, and waste disposal” without tissues and organs.

Introduction: All sponges belong to the phylum Porifera. They are the simplest animals with the cellular level of organization. They have diverged forms than other animals early in evolution. Most of the body parts of sponges are asymmetrical. Sponges consist of pores in their body called ostia.

Explanation of Solution

The sponges have a relatively simple body plan with all cells of the body in direct contact with water. This allows excretion and exchange of gases to occur through diffusion. The sponges are filter feeders and contain choanocytes (collar cells) that help them to get food. The beating of flagella of choanocyte draws food particles along with water. The food particles stick to collar-like projections of the choanocytes. The food particles are then phagocytized and are either digested or passed on to the other cells called amoebocytes. These amoebocyte cells then transfer it to other cells of the body.