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.
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:
- They possesses 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
- 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
Tags
B.sc ZOOLOGY