NEET Practice Questions (MCQs) with Answers & Solutions

The provided diagram and text state, Vertebrata is divided into Agnatha (lacks jaw) and Gnathostomata (bears jaw). Class 1. Cyclostomata falls under Agnatha.

Cyclostomata are jawless vertebrates ('without jaws'), whereas Chondrichthyes have jaws ('Their jaws are very powerful'). While both have gill slits, cartilaginous skeletons, and marine habitats (at least predominantly for Chondrichthyes), the presence or absence of jaws is a fundamental differentiator between Agnatha (which includes Cyclostomata) and Gnathostomata (which includes Chondrichthyes).

The NCERT states, Their larvae, after metamorphosis, return to the ocean.

The NCERT text specifies, They have an elongated body bearing 6-15 pairs of gill slits for respiration. Cyclostomes have a sucking and circular mouth without jaws. Their body is devoid of scales and paired fins.

For Cyclostomata, the NCERT states, Cranium and vertebral column are cartilaginous. For Chondrichthyes, it says, They are marine animals with streamlined body and have cartilaginous endoskeleton. Therefore, a cartilaginous endoskeleton is a shared feature. Placoid scales, ventrally located mouth, and operculum are characteristic of Chondrichthyes, not Cyclostomata.

The NCERT states, 'The members of subphylum Vertebrata possess notochord during the embryonic period. The notochord is replaced by a cartilaginous or bony vertebral column in the adult.' While it doesn't explicitly state the notochord's persistence in Cyclostomata adults, it does specify their vertebral column is cartilaginous, not bony. More importantly, the summary states, 'Agnatha is represented by the class, Cyclostomata. They are the most primitive chordates.' This makes statement III correct. Statements I and II are incorrect as the vertebral column is cartilaginous and chordates (which vertebrates are) have a notochord during embryonic development, which is then replaced by a vertebral column (cartilaginous in cyclostomes).

According to the NCERT text, 'A very significant contribution of mitosis is cell repair. The cells of the upper layer of the epidermis, cells of the lining of the gut, and blood cells are being constantly replaced.' Options 1, 2, and 4 are associated with meiosis.

The NCERT text states, 'Mitotic divisions in the meristematic tissues – the apical and the lateral cambium, result in a continuous growth of plants throughout their life.' Meristematic tissues are responsible for growth.

The context clearly states, 'Since the number of chromosomes in the parent and progeny cells is the same, it is also called as equational division.' Options 1 and 2 describe meiosis, and option 4 is incorrect for mitosis.

The NCERT text mentions, 'However, in some lower plants and in some social insects haploid cells also divide by mitosis.' and also 'However, there are few exceptions to this where haploid cells divide by mitosis, for example, male honey bees.' This indicates that it's not a universal phenomenon but specific exceptions.