Chapter 27, Problem 19A

Summary Introduction

Introduction: Chordates are species belonging to the phylum Chordata that at some stage during their development have four distinctive characteristics-a dorsal tubular nerve cord, pharyngeal pouches, a notochord and a postanal tail.

Answer to Problem 19A

Correct answer:

The correct answer is option (D) dorsal tubular nerve cord, notochord, pharyngeal pouches, postanal tail

Explanation of Solution

Explanation/justification for the correct answer:

Option (D) dorsal tubular nerve cord, notochord, pharyngeal pouches, postanal tail. Chordates contain notochord just below the dorsal tubular nerve cord, pharyngeal pouches that link the muscle tube that connects the cavity of the mouth and the esophagus and postanal tail used for locomotion and situated behind the digestive system and anus. So, the correct answer is option (D).

Explanation for incorrect answer:

Option (A) water-vascular system, notochord, pharyngeal pouches, postanal tail. Chordates contain notochord just below the dorsal tubular nerve cord, pharyngeal pouches that link the muscle tube that connects the cavity of the mouth and the esophagus and postanal tail used in the locomotion and situated behind the digestive system and anus. However, chordates do not have water-vascular system. So, this is an incorrect answer.

Option (B) tunic, pharyngeal pouches, dorsal tubular nerve cord, postanal tail. Pharyngeal pouches connecting the muscle tube which connects the cavity of the mouth and the esophagus. In chordates, the dorsal tubular nerve cord is dorsal to or above the digestive organs, and is in the form of a tube. Postanal tail situated between the digestive system and anus, use in locomotion. Chordates have no tunic. So, this is an incorrect answer.

Option (C) tube feet, notochord, pharyngeal pouches, postanal tail. Chordates contain notochord just below the dorsal tubular nerve cord, pharyngeal pouches that link the muscle tube that connects the cavity of the mouth and the esophagus and postanal tail used for locomotion and situated behind the digestive system and anus. Chordates have no tube feet. So, this is an incorrect answer.