Chapter 27, Problem 4STP

Summary Introduction

Introduction:

Echinoderms are the major group of marine animals that have endoskeleton that is spiny and also has tube feet. Echinoderms belong to the phylum Echinodermata. They possess radial symmetry around a central disk. All of them have a very special vascular water system. Echinoderms are distinguished by these special features from other species in the animal world. The excretory system is absent in phylum Echinodermata.

Answer to Problem 4STP

Correct answer:

The correct answer is option (C) deuterostome development.

Explanation of Solution

Explanation/justification for the correct answer:

Option (C) deuterostome development. All vertebrates are chordates. Echinoderms and chordates both develop deuterostomes. These are the common characteristics that have an evolutionary connection between echinoderms and vertebrates. So, this is the correct answer.

Explanation for incorrect answer:

Option (A) bilateral symmetry as adults. The echinoderms have a bilaterally symmetrical body as larvae that turn to radially symmetrical adults. Though vertebrates are bilateral symmetry in echinoderms, the adults are recognized by their radial symmetry. So, this is an incorrect option.

Option (B) free-swimming larvae. The echinoderms start as bilateral free-swimming larvae and develop into radially symmetrical adults whereas in vertebrates we do not see free-swimming larvae. So, this is an incorrect option.

Option (D) radial symmetry as larvae. The echinoderms have radial symmetry that is not as larvae but as an adult. They develop a bilaterally symmetrical body as larvae that give rise to a radially symmetrical body as an adult. So, this is an incorrect answer.