Question

All protochordate are
(a) Aquatic
(b) Marine
(c) Freshwater
(d) All of the above

Answer 1

Protochordates are the organisms that do not have a proper taxonomic group and form a major division of Chordata which are also known as Acraniata due to the absence of a true skull.

Complete answer:
All protochordate are marine. They are closely related to the vertebrates which are different from the chordates by the absence of a backbone. Protochordate is found in marine water and is bilaterally symmetrical. They are triploblastic and coelomate with a long, rod-like structure at a certain stage of their body development which supports the structure and is known as the notochord. They are composed of organ system level of organisation which are seen in herdsman and amphioxus. The presence of notochord makes the chordates different from the protochordate as they lack a true notochord. The notochord arises from the mesoderm and protects the chordates during their embryonic stage. Humans possess notochord at their embryonic stage.
Protochordate is divided into hemichordate, Urochordata and Cephalochordata. The hemichordate is found in marine water which lives solitarily and possesses a cylindrical and unsegmented body. There is fire with the help of gills and a complete digestive system with a circular system of a heart with two longitudinal vessels. Urochordata are sessile organisms that are found in Marine environments and have a notochord at their larval stage in the tale of the larva which disappears on moving adults. They respire through gills and are composed of an open circulatory system and lack excretory organs. Cephalochordata is marine organisms that have notochord throughout their life and respire through gills.

So, the correct answer is 'marine'.

Note:
The body of the protochordate is divided into proboscis, collar and trunk with the collar that bears arms and tentacles. Urochordates are also known as tunicates due to the presence of a covering of leathery tunic in its adult form that supports and protects the animal.