Chapter 27, Problem 6STP

Summary Introduction

Introduction:

Vertebrate chordates include the major part of the vertebrates. The phylum chordates have vertebrates like fishes, amphibians, reptiles, mammals. There is a great diversity in vertebrates of fishes, amphibians, etc.

Answer to Problem 6STP

Correct answer:

The correct answer is option (B) 2.

Explanation of Solution

Explanation/justification for the correct answer:

Option (B) 2. The indicated arrow number 2 in the image shows a notochord. In vertebrate chordates, the notochord is replaced by bones and cartilage but in invertebrate chordates, the notochord remains as the notochord. So, this is the correct answer.

Explanation for incorrect answer:

Option (A) 1. The number 1 in the image indicates the dorsal tubular nerve cord. The dorsal tubular nerve chord is one of the distinctive features of the phylum chordates but it is not replaced by bones and cartilage in vertebrate chordates. So, this is an incorrect option.

Option (C) 4. The number 4 in the image indicates pharyngeal pouches. Pharyngeal pouches in chordates are paired structures. It is not replaced by bones and cartilage in vertebrate chordates. So, this is an incorrect option.

Option (D) 5. The number 5 in the image indicates the ancestral thyroid gland. The ancestral thyroid gland in chordates regulates growth, metabolism, and development. It does not change to bones and cartilage in vertebrate chordates. So, this is an incorrect answer.