Chapter 29, Problem 1STP

Summary Introduction

Introduction:

Echinoderms are aquatic creatures with spiny endoskeletons, water-vascular structures, and tube legs. They have radial symmetry as adults Echinoderms are deuterostoms. Approximately 6000 living species of echinoderm are marine animals.

Answer to Problem 1STP

Correct answer:

The correct answer is option (A) Calcium carbonate plates with spines covered with a thin skin.

Explanation of Solution

Explanation/justification for the correct answer:

Option (A) Calcium carbonate plates with spines covered with a thin skin. Echinoderms are the first group of animals to have endoskeletons in evolutionary history. In echinoderms, the endoskeleton consists of calcium carbonate plates, frequently attached to the spines and covered by a thin layer of skin. So, the correct answer is option (A).

Explanation for incorrect answer:

Option (B) Calcium carbonate spines that protrude through the skin. In echinoderms, the endoskeleton consists of calcium carbonate plates, often with spines attached and is covered by a thin layer of skin. So, this is an incorrect option.

Option (C) Silicon plates with spines covering the entire surface. In echinoderms, the skin is covered by the calcium carbonate plates with spines. So, this is an incorrect answer.

Option (D) Silicon spines that protrude through the skin. The echinoderms have calcium carbonate spines that cover the skin. So, this is not the correct option.