Comparison Chart Of Chordates And Non-Chordates — With Examples | BSc Zoology Notes

Introduction

When we study the Animal Kingdom, the very first and most significant division we encounter is based on the presence or absence of a structure called the notochord. Animals that possess a notochord at some stage of their life are placed under Phylum Chordata, while all remaining animals that never develop a notochord fall under the broad category of Non-Chordates.

What are Chordates and Non-Chordates?

• Chordates are animals that possess a notochord at some stage of their life cycle. They also typically show characteristics such as a dorsal hollow nerve cord, pharyngeal gill slits, and a post-anal tail. Examples of chordates include fish, amphibians, reptiles, birds, and mammals.
• Non-chordates are animals that do not possess a notochord at any stage of their life. They form the majority of the animal kingdom and include groups such as Porifera, Cnidaria, Annelida, Mollusca, and Arthropoda.
• The classification of animals into chordates and non-chordates is one of the most fundamental divisions in zoology and helps in understanding the evolutionary relationships among animals.

 Connecting Link — Balanoglossus

• No discussion of Chordates and Non-Chordates is complete without mentioning Balanoglossus — the most famous connecting link between the two groups.
• Balanoglossus belongs to Phylum Hemichordata and shows characters of both groups:

Chordate characters in Balanoglossus:

• They possess pharyngeal gill slits
• They has a dorsal hollow nerve cord in the collar region
• They has a stomochord in the proboscis which is a notochord-like structure

Non-chordate characters in Balanoglossus:

• Overall body plan resembles annelids
• Open circulatory system
• No true notochord or vertebral column

 Did You Know?

Nearly 95% of all animal species on Earth are Non-Chordates. Yet despite being just 5% of the animal kingdom, Chordates have come to dominate every major habitat on the plane from the deepest ocean trenches to the highest mountain peaks!

Referrence :- 

• NCERT Biology Class 11
• P. S. Verma & V. K. Agarwal — Chordate Zoology
• R. L. Kotpal — Modern Textbook of Zoology
• Jordan & Verma — Invertebrate Zoology