Question

Which of the following statements are true for the phylum Chordata

1. In Urochordate notochord extends from head to tail and it is present throughout their life.
2. In Vertebrates notochord is present during the embryonic period only.
3. The central nervous system is dorsal and hollow.
4. Chordata is divided into 3 subphyla: Hemichordate, Tunicata, and Cephalochordate.

• A. 1 and 2
• B. 2 and 3
• C. 3 and 4
• D. 3 and 1

Answer 1

The correct option is B

2 and 3

The correct option is B.

Explanation for the correct options:

Statement 2:

1. All the members of vertebrates contain a notochord during the embryonic stage which is later replaced by a bony vertebral column.
2. It is present from the head to the tail of the organism and in between the digestive tube and nerve cord.
3. Most species in the phylum Chordata, which includes creatures with backbones, are vertebrates (subphylum Vertebrata).

Statement 3:

1. Only one embryonic characteristic, the dorsal hollow nerve cord, is shared by all chordates, the others being the notochord, post-anal tail, endostyle, and pharyngeal slits.
2. A hollow cord that is dorsal to the notochord is known as the dorsal hollow nerve cord.
3. A section of the ectoderm that rolls into a hollow tube create it.
4. The CNS is ventral and solid in case of non-chordates.

Explanations of incorrect options:

Statement 1:

1. In Urochordata, notochord is present only in larval tail.
2. Tadpoles go through retrogressive metamorphosis, and the notochord and nerve cord that are destroyed during transformation and are absent in adulthood.

Statement 4:

1. According to the prevalent theory, there are three subphyla that make up the phylum Chordata: Urochordata (Tunicata), Cephalochordata, and Vertebrata.
2. The notochord, a dorsal, hollow neural tube (nerve cord), branchial slits, an endostyle, myotomes, and a postanal tail are shared by all three groups.

Final answer: The correct statements are 2 and 3 - ‘In vertebrates notochord is present during the embryonic period only’ and ‘ The central nervous system is dorsal and hollow.’