Chapter 27.2, Problem 4MI

Summary Introduction

To Identify:

The four distinctive features of chordates and their location on the animal along with the explanations of benefits of each feature.

Introduction:

Invertebrate chordates such as Amphioxus , Tunicate are the animals which possess a notochord at some point in their development.

Explanation of Solution

The four distinctive features of chordates and their location on the animal are given below:

Feature	Location	Benefits
Notochord	It is located just below the dorsal tubular nerve cord and runs the length of the body	It enables body to bend, rather than shorten, during contraction of muscle segments; for first time enabled side-to-side, fishlike swimming motion.
Post-anal tail	It is located behind the digestive system and anus	It can propel an animal with more powerful movements than the body structure of invertebrates without a post-anal tail.
Dorsal tubular nerve cord	It is located above the digestive organs	During development, anterior end becomes the brain and posterior end becomes the spinal cord.
Pharyngeal pouches	It connects the muscular tube that links the mouth cavity and esophagus.	They evolve into gills in aquatic chordates; develop into structures such as tonsils and thymus gland in terrestrial chordates.