Buccal cavity - class-XII

The adult human dental formula represents the number of teeth in one half of each jaw: 2 incisors, 1 canine, 2 premolars, and 3 molars.

Walrus tusk ivory comes from two modified upper canines. It is also known as 'morse'. Walrus teeth are also commercially carved and traded. The average walrus tooth has a rounded, irregular peg shape and is approximately 5 cm in length.

Rats have incisors and molars. Incisors are the foremost teeth in mammals. In rats, there are four, long, sharp front teeth, two on top and two on the bottom. They are specialized for gnawing. Molars are rearmost teeth in the mouth of rat used for grinding food prior to swallowing it. Rats have 12 molars, six on top and six on the bottom. Rats do not have canines (the conical, pointed teeth used for holding prey, defense) or premolars (grinding teeth behind the canines and in front of the molars).
Thus, the correct answer is option D.

Elephants have 26 teeth- 2 incisors (known as tusks), 12 deciduous premolars and 12 molars.
Rats have 8 teeth on the lower jaw and 8 on the upper jaw, a total of sixteen teeth which consists incisor, premolar and molar.
Thus, the correct answer is option D.

The incisors and cheek teeth of rabbits are called aradicular hypsodont teeth. This is sometimes referred to as an elodent dentition. These teeth grow or erupt continuously. The growth or eruption is held in balance by dental abrasion from chewing a diet high in fibre. The anatomic dental formula is 2( i2/1 c0/0 m3/2 )= 16  deciduous teeth.

The dental formula of adult elephants for both species is I 1/0 C 0/0 PM 3/3 M 3/3, with a total number of 26 teeth. The two upper incisors are the tusks.

The standard dental formula for an adult human is 2123/2123, representing the teeth in one half of the upper and lower jaws.

A child's dental formula lacks premolars and has only two molars in each half-jaw, resulting in 2102/2102.

A dental formula is a shorthand representation of the number and type of teeth present in one half of the upper and lower jaws.

Statement 1 is correct as the dental formula represents half of each jaw. Statement 2 is incorrect because dental formulas are specific to mammals and are not typically applied to non-mammalian vertebrates in the same way.

In each set of teeth, incisors (I) are indicated first, canines (C) second, premolars (P) third, and finally molars (M), giving I:C:P:M which is the minimum number of teeth in one half of one jaw. 

There is only one set of teeth functional throughout life with the exception of a milk molar which is replaced by the last premolar. Incisors are more numerous than in placentals. 3 premolars and 4 molars as against 4 P and 3 M in placentals. Dentition in opossum is I 5/4, C 1/1, P 3/3, M 4/4. 

The uvula is a fleshy extension that hangs from the back of the soft palate.

During swallowing, the soft palate and uvula move upward to close off the nasopharynx, preventing food from entering the internal nares.