Question

What type of dentition is seen in mammals? What are the elephant tusks?

Answer 1

Hint: Dentition is the number, kind, arrangement, and structure of the teeth. In addition, we should also know that the tusks of an elephant(mammal) are the modified teeth.

Complete answer: The dentition is defined as the number, kind, arrangement, and structure of teeth. The dentition of mammals is determined on the following criteria –
1. Dentition on the basis of origin: In mammals, thecodont dentition is found on the basis of origin. This means that the teeth are embedded in the bony sockets.
2. Dentition on the basis of appearance: In mammals, monophyodont and diphyodont dentition is found on the basis of appearance. The monophyodont dentition is the one in which the teeth appear once in a lifetime. The diphyodont dentition is the one in which the teeth appear twice in a lifetime.
3. Dentition on the basis of function: In mammals, homodont and heterodont dentition is found on the basis of function. The homodont dentition is the one in which all the teeth have the same function. The heterodont dentition is the one in which all the teeth have different functions.
4. Dentition on the basis of shape: In mammals, selenodont, bunodont, secodont, and lophodont dentition is found on the basis of shape. The selenodont dentition is the one in which the teeth have crescent-shaped cusps. The bunodont dentition is the one in which the teeth have cusps. The secodont dentition is the one in which the teeth are pointed and sharp. Lastly, the lophodont dentition is the one in which a transverse ridge is found in the teeth.
The tusks of an elephant are the second pair of incisors in the upper jaw. The upper incisors have no roots in them so they grow to form tusks. The lower incisors are absent. The tusks are made up of a substance called ivory. Ivory is a special type of dentine. Tusks are used for fighting as well as protection.

Note: The elephant possesses the minimum number of teeth amongst the mammals. The total number of teeth in an elephant is 14. The dentine formula of an elephant is as follows –
\[\begin{array}{*{20}{c}}1&0&0&3\\\hline0&0&0&3\end{array}\]
From this dentine formula we can infer that in one half of the upper jaw, an elephant has 1 incisor and 3 molars. This incisor is the modified tusk. In the lower jaw, only 3 molars are present.