Chapter 26, Problem 2STP

Summary Introduction

Introduction :

The arthropods are divided into groups according to the body segment, mouthparts, and appendages of their body. The groups include crustaceans, spiders and their relatives, and insect and their relatives. The crustaceans have two pairs of antennae, mandibles, two compound eyes, five pairs of legs, and they are swimmers. The spiders and their relatives do not have antennae, six pairs of legs, and two body sections. The insects and their relatives have antennae, three pairs of legs, and three body areas.

Answer to Problem 2STP

Correct answer :

The correct answer is option (B) crustaceans.

Explanation of Solution

Explanation/justification for the correct answer :

Option (B) crustaceans. The crustaceans include shrimps, crayfish, and lobster. They are marine organisms also found in freshwater and terrestrial body. They have four pairs of legs and they can even swim. They have two pairs of antennae and have mandibles. So, the correct answer is option (B).

Explanation for incorrect answer :

Option (A) copepods. Copepods are a group of crustaceans that are smaller in size, found in the saltwater and freshwater. They have segmented bodies and segmented appendages that allow them to swim. So, this is an incorrect option.

Option (C) insects. The insects are the group of arthropods that have three pairs of legs, the body is divided in three areas, and they have antennae. So, this is an incorrect answer.

Option (D) spiders. Spiders are the group of arthropods that have six pairs of legs, have two section of body, and do not have antennae. So, this is an incorrect answer.