Question

explain the basis of grouping organism into chordata and non chordata

Answer 1

The kingdom Animalia is divided into chordates and non-chordates based on the presence or absence of the notochord. 
Chordates are the group of animals that have a notochord while the non chordates lack notochord.
Any organism that has a notochord or a vertebral column (also known as spine or backbone) comes under the group chordates.
eg (birds, animals, humans, etc)
the organisms that do not have spinal chords are known as non chordates.

Answer 2

Animals is divided into chordates and non-chordates!