28-1 Introduction to the Arthropods

Exoskeleton

• External skeleton; tough external covering that protects and supports the body of many invertebrates.

Chitin

• Complex carbohydrate that makes up the cell walls of fungi; also found in the external skeletons of arthropods.

Appendage

• Structure, such as a leg or antenna, that extends from the body wall.

Tracheal tube

• One of many branching, air-filled tubes that extend throughout the bodies of many terrestrial arthropods.

Spiracle

• Small opening located along the side of the body through which air enters and leaves the body of many terrestrial arthropods.

Book Lung

• Organ that has layers of respiratory tissue that is used by some terrestrial arthropods for the exchange of gases.

Malpighian tubule

• Saclike organ in most terrestrial arthropods that extracts wastes from the blood, adding them to feces that move through the gut.

Molting

• Process in which an arthropod sheds its exoskeleton and manufactures a larger one to take its place.

Key Concept

• Arthropods have a segmented body, a tough exoskeleton, and jointed appendages.

Key Concept

• The evolution of arthropods, by natural selection and other processes, has led to fewer body segments and highly specialized appendages for feeding, movement, and other functions.

Key Concept

• When they grow their exoskeletons, arthropods undergo periods of molting.