Chapter 19, Problem 1RQ

Summary Introduction

To discuss: The important distinguishing features of arthropods.

Introduction: Arthropods are the protostomes and belong to the ecdysozoan branch. More than ¾ of all known species belong to this group. Arthropods have specific features that allow them to inhabit a wide range of habitat.

Explanation of Solution

Arthropods are bilaterally symmetrical, triploblastic organisms with an organ system level of body plan. They have a complete digestive tube. Presence of a segmented body, a hard exoskeleton composed of chitin and protein, and the paired jointed appendages are the characteristic features of arthropods. The appendages are modified for various functions such as swimming paddles, walking legs, mouthparts, and sensory organs.

The nervous system consists of a brain and ventral nerve cord with ganglia. Some arthropods such as insects and many crustaceans have compound eyes composed of many light-sensitive units called ommatidia. Arthropods have an open circulatory system and a dorsal, tubular heart. Arthropods have gills, tracheae, or book lungs for breathing. They have a complete digestive system. Different classes of arthropods have various excretory structures. For example, two or more malpighian tubules receive metabolic wastes from the blood in insects and serve as structures of excretion.