Chapter 24.3, Problem 3MI

Summary Introduction

To define:

The terms medusa, polyp, nerve net, gastrovascular cavity, nematocyst, cnidocyte, sessile, and filter feeder.

Introduction:

A cell is the structural, functional, and biological unit of all living organisms. It is smallest unit for life. A cell can be prokaryotic or eukaryotic. Eukaryotic cells contain membrane bound cell organelles, that help in functioning of cellular machinery by carrying out biochemical reactions.

Explanation of Solution

Medusa − It is a type of body form found in phylum Cnidaria that are invertebrates. The medusa body is umbrella shaped or bell shaped. Their mouth opens into the main body cavity.

Polyp − It is small clump of cells that grows inside animal’s body. They are of two types, pedunculated polyps and sessile polyps. Pedunculated polyps hang from a stalk, while sessile polyps are flat.

Nerve net − It is the diffused network of cells that together forms ganglia in some living beings. It can be easily found in nerve net.

Gatsrovascular cavity − It is a structure that is found in primitive animals. It functions to digest food and transport nutrients throughout the body.

Nematocyst − It is a special cell found in the tentacles of jellyfish and some coelenterate. It is used for killing prey and in self-defence.

Cnidocyte − It is an explosive cell that contains cnidocyst, a secretory organelle. Cnidocyst transfers sting to other living beings. Cnidocytes are found near the mouth and the tentacles and helps in preying and repelling predators.

Sessile − Sessile organisms are found attached permanently to something. An external force is required to move them from their location.

Filter feeder − These are suspension feeding animals that feed food which is strained from water. Filter feeding is seen in invertebrates and some vertebrates like baleen whales.