Question

Nerve cord of chordates is
A. Dorsal
B. Hollow
C. Ventral
D. Both A and B

Answer 1

Hint: The kingdom Animalia has various phyla with various characteristic features. There are certain features that are observed only at a particular point in time, like the embryonic stage. Later on, either they become vestigial or form some other important organs or part of the body system.

Complete answer:
The dorsal hollow nerve cord is only one embryonic feature unique to all chordates, among the other four chordate features; a notochord, a post-anal tail, an endostyle and pharyngeal slits. The dorsal hollow nerve cord is a hollow cord dorsal to the notochord. It is formed from a part of the ectoderm that rolls, forming the hollow tube. The phylum Chordata is subdivided into Urochordata, Hemichordata and Cephalochordata.
Dorsal: Chordates have a dorsal nerve cord. It is their defining feature in the embryonic stage. It is formed from ectoderm.
Hollow: Nerve cords in chordates are hollow. It develops into the central nervous system including the brain and spinal cord.
Ventral: There is no ventral nerve cord in chordates. It is the feature of the invertebrates.
Hence, the correct answer is Option (D).

Note:
i. Urochordata: They are called sea squirts. They are a member of phylum Chordata. They have notochord present only in the larval tail stage. They have an open circulatory system. They can squirt the water from their body.
ii. Hemichordata: They were initially under Chordate phylum but are now under the marine deuterostome. They have cilia all over their surface and have an open circulatory system.
iii. Cephalochordate: They are a member of the phylum Chordata. They are segmented marine animals. They are very small. They feed on microorganisms and have a closed circulatory system.