Question

Problem 23

Answer 1

Background and context

Chordates are the most highly evolved multicellular animals and belongs to phylum Chordata. They are characterized by four basic features present either throughout or during early embryonic life. The distinctive features of chordates are notochord, dorsal hollow central nervous system, pharyngeal gill slits, tails.

The phylum is divided into three sub-phyla - the first two are small groups of primitive chordates and are collectively called lower chordates or protochordates. Vertebrates are commonly called highly chordates.