Question

What is meant by notochord and what is the difference between Chordata and protochordata?

Answer 1

Notochord is a long flexible rod like structure present in all chordates which separates the nervous system from the gut. It is present in the embryo of all chordates and also in some adult chordates. The main function of notochord is to support the body.

Animals that have notochord are categorised into chordata.
Phylum chordata is further divided into sub phyla Protochordata and Vertebrata.

Protochordates are exclusively marine and posses notochord at larval stage only or through out the life.
Vertebrates posses notochord in early embryonic stage only. It gets replaced by cartilaginous or bony vertebral column in adults.