Question

Which of the following statements is(are) not true?
A. In Urochord, the notochord is present only in the larval tail.
B. In Cephalochordates, the notochord extends from head to tail region.
C. Branchiostoma belongs to Hemichordates
D. Only one class of living members, class Cyclostomata represents the superclass Agnatha
A) A B and D only
B) A, C and D
C) C only
D) A and D only
E) C and D only

Answer 1

Hint: Animal bodies featured with the presence of notched during any point of their lifespan are termed as the chordates. The members of this group are characterized by Pharyngeal gill slits and hollow nerve cord.

Complete step by step answer: Branchiostoma is one of the few living genera of lancelets. It is not a hemichordate but a Cephalochordate in fact. These are snake-like organisms and are close relatives of vertebrates. Unlike vertebrates, they do not have a true head with a skull capsule, eyes, nose, a well-developed brain. They have gill-slits enlarged anterior end of the dorsal nerve cord above and in front of them. In some animals, the presence of chordate can be found in the entire body from head to tail, whereas, in some animals, it is present only in the parts of their larval tail. Urochord or tunics are marine organisms. These are filter-feeding animals. When the Larva undergoes metamorphosis, the notochord in the tail and nerve cord degenerates. This is called retrogressive metamorphosis. There is a loss of advanced features while the development of larvae to adults. The Cephalochordates or lancelets have a long body. The body tapers or is pointed at both ends with a large notochord, that extends from tip to tip and is present throughout life.
Hence, the correct answer is option C.

Note: Cephalochordates possesses a notochord and nerve cord, pharyngeal slits, and a post-anal tail in the adult stage. They do not have a true brain but the notochord extends into the head which gives the subphylum its name is Cephalochordates.