Question

Assertion :Some vertebrate embryos develop a series of six pair aortic arches. Reason: These aortic arches were gradually dropped out during the development.

• A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion.
• B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion.
• C. Assertion is correct but Reason is incorrect.
• D. Both Assertion and Reason are incorrect.

Answer 1

The correct option is B Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion.

The aortic arches or pharyngeal arch arteries (once referred to as branchial arches in human embryos) are a series of six paired embryological vascular structures which give rise to several major arteries. They are ventral to the dorsal aorta and arise from the aortic sac. The aortic arches of vertebrate animals form the arterial supply route to the tissues. In the embryo aortic arches develop in association with each of the developing pharyngeal arches. Typically, a total of six arches come into being in the developmental process, all thought some are also lost early in their development. In the illustration below, the basic embryonic pattern of aortic circulation is shown, and the fates of those arches in several representatives of the major vertebrate groups. Note that the ventral aorta extension remains as the external carotid in all groups, and the anterior extension of the dorsal aorta becomes cut off from the posterior reaches in most tetrapods to become the isolated internal cartotid. Also the fourth arch becomes the primary supply to the dorsal aorta in all tetrapods, while the sixth aortic arch forms the base of the pulmonary arteries, So, Some vertebrate embryos develop a series of six pair aortic arches and these aortic arches were gradually dropped out during the development. Thus, both Assertion and Reason are correct but Reason is not the correct explanation for Assertion. Thus, option B is correct.