Question

Which of the following is not one of the basic characteristics of chordates?
A. A dorsal supporting rod called a notochord
B. A tail
C. A dorsal tubular nerve cord
D. Pharyngeal pouches that develop into gills and lungs in humans

Answer 1

Hint: All chordates are characterized by four main distinguishing features. These are:
At some stage in the life cycle of chordates, notochord is present.
Dorsal and hollow central nervous system.
At adult or embryonic stage, gill slits are present in the pharynx.
A tail which is absent or reduced in many adult chordates.

Complete answer:
Option A. A dorsal supporting rod called a notochord: Notochord is situated on the dorsal side between the dorsal hollow nerve cord and the alimentary canal. It is a solid unjointed, stiff but flexible structure in the body of chordates. Presence of notochord is one of the basic characters of chordates which is present in larval stage and disappears in the adult in some, it may persist throughout life and in advanced chordates it is replaced by bony or cartilaginous vertebral column.
Option A is not correct.
Option B. A tail: A tail is reduced or absent in many of the adult chordates but the presence of it is one of the characters of all chordates. It is a postanal part of the body. It may be present in the larval stage, throughout life or present just in the embryonic stage.
Option B is not correct.
Option C. A dorsal tubular nerve cord: A dorsal, hollow or tubular nerve cord or the central nervous system is present in chordates. It is always hollow and lies dorsal to the notochord. It is also found in the larval stage but later replaced by a dorsal ganglion in the adult urochordates. Vertebrates have developed the central nervous system. These are advanced chordates.
Option C is not correct.
Option D. Pharyngeal pouches that develop into gills and lungs in humans: Having pharyngeal (throat) pouches with arches of arteries in them gill slits to the outside is the distinguishing character of chordates. All chordates at some stage of life have a series of paired narrow openings (gill slits) on the lateral side of the pharynx but no pharyngeal pouches that develop into gills and lungs in humans.

Therefore, Option D is correct.

Note:
Other characters of chordates are: bilateral symmetry, three germinal layers, segmentation, cephalization, coelom, endoskeleton, complete digestive tract, special organs for respiration and excretion, closed circulatory system, organ-system level of organization. Sexes are seperate, reproductive glands or gonads with gonoducts and without asexual reproduction. Heart is ventral. If RBCs are present, they contain respiratory pigment known as haemoglobin.