Question

Vertebrates and tunicates share

(A) jaws adapted for feeding.

(B) a high degree of cephalization.

(C) an endoskeleton that includes a skull.

(D) a notochord and a dorsal, hollow nerve cord.

Short answer

(A) The statement“jaws adapted for feeding” is false.

(B) The statement “a high degree of cephalization” is false.

(C) The statement “an endoskeleton that includes a skull” is false.

(D) The statement “a notochord and a dorsal, hollow nerve cord” is true.

Step-by-step solution

Phylum Chordata

In the phylogenetic tree of animals, the clade Deuterostomia comprises three distinct phyla, the phylum Chordata being one of them. Ther are three sub-phyla within this phylum; one is Vertebrata, and the other two are invertebrate groups (urochordates and cephalochordates).

Explanation of option ‘(A)’

The tunicates are animals belonging to the urochordate group, and they inhabit marine ecosystems. These animals obtain food by the filter-feeding mechanism (facilitated by siphon) and lack jaws. In contrast, jaws are present in vertebrates.

Thus, tunicates lack jaws and feed with the help of a siphon.

Therefore, the given statement is false.

Explanation of option ‘(B)’

The term cephalization refers to the arrangement of nervous system organs at one terminal region of the body. This type of organization is distinctly observed in vertebrates, but it is absent in the case of tunicates.

Thus, a high degree of cephalization is found only in vertebrates and not in tunicates.

Therefore, the given statement is false.

Explanation of option ‘(C)’

The process of cephalization in vertebrates resulted in a body structure that the nervous system organs were arranged at the head region. These organs remain protected within an endoskeleton immovable structure called the skull. Tunicates do not have any such protective structure.

Thus, the endoskeleton structure is found only in the case of vertebrates.

Therefore, the given statement is false.

Explanation of option ‘(D)’

The phylum chordates have two features that distinguish them from all other animal groups. These are the presence of notochord (regulates skeletal development in an adult body) and the presence of dorsally placed nerve cord that is hollow (it forms units of the central nervous system in adult animals).

Thus, the notochord and dorsally placed hollow nerve chord are shared by all chordate organisms.

Therefore, the given statement is true.