Question

Which of these is not an example of protochordata?
A. Balanoglossus
B. Herdemania
C. Amphioxus
D. Asterias

Answer 1

Hint: The protochordates contain hollow dorsal nerve cord, gill slit and stiff supporting rod called notochord . The protochordates differ from vertebrates as they do not contain backbone.

Complete answer:
 Protochordates are the informal group of species called invertebrate animals which are closely related to vertebrates. Protochordates are divided into subcategories according to the notochord they possess.
1) Hemichordata: These are marine organisms with an unsegmented, cylindrical body. They look like worms. Hemichordata use filtering to feed on microorganisms. The mode of reproduction is asexual with united or separate sexes in organisms. Example-Balanoglossus. 2)Urochordata: are marine organisms and mostly sessile in nature. The body is bounded in a leathery sheath called tunicates that are made up of tunicin. In Urochordata the Notochord is only present in larvae, not in adults. They do not have an excretory system. The mode of reproduction is asexual. Example- Herdmania 3) Cephalochordata: are the free swimmers and their tail stay throughout their lives. The body of cephalochordates are made up of myotomes and the body is fish-like. Example-Amphioxus Asterias or star fish is an example of Echinodermata. They contain a rigid calcium carbonate structure as a skeleton.

Hence, the correct answer is option (D).

Additional information:
Characteristics of Notochord- a)A notochord containing turgid cells looks like a rigid, unsheathed rod like which is present throughout their lives. b) Protochordata are mainly found in marine water. c) Central Nervous System of protochordata is single, hollow and dorsal d) Body is triploblastic, bilaterally symmetrical with organ system of organization.

Note: Notochord is a long rod like structure that extends around the back of an animal dividing the gut tissue from the gut. It has a place for muscles to attach which helps in the movement. Protochordates do not contain notochord at all their time or throughout their life.