Question

Study the following passage: Most of the vertebrates have jaws with teeth. The mode of arrangement on the jaw is called dentition. The various types of teeth seen in mammals are incisors (I) canines(C) Premolars (P) and molars (M). They are used for biting, tearing, chewing and grinding respectively. Canines, the tearing teeth are well-developed in carnivores and ill- developed or absent in herbivores. Now answer the following: (i) In frogs, all the teeth in the upper jaw looks alike, whereas in human beings they are different. The type of dentition in man can be called……. A) Homodont B) Isodont C) Heterodont D) Acrodont
(ii) The dental formula of a mammal is written as ICPM=2023 ̸ 1023. The teeth missing in it are: A) incisors B) canines C) premolars D) molars

Answer 1

Hint: Teeth are rigid, off white colour and contains calcium. Herbivores animals contain more molar teeth than humans whereas carnivores animals have scissor-like sharp teeth.

Complete answer:
(i) Homodont dentition: The teeth are anatomically and functionally same meaning all the teeth in jaw looks alike. Mostly found in frogs, fishes. Isodont dentition: The teeth have the same tooth morphology. Mainly found in snakes Acrodont dentition: The teeth have no roots and are attached at the base of jawbone. Heterodont dentition: These are the four different teeth designed for different purposes. The four different teeth present in humans are: 1) Incisors: are the front teeth which are present in both upper and lower jaws. There are eight incisors present in front and at the centre. The function of incisors is in cutting the food. 2) Canines: These are the sharp teeth for tearing food. There are four canines present. Canines start coming when the infant is 20 months. 3) Premolar: are used to crush the food. There are four premolars present on each side. They are present two in each quadrant of the mouth.
4) Molars: are the posterior teeth which have a flat surface to grind the food. In total there are twelve molars present in permanent dentition. Therefore the correct answer is C Heterodont dentition
(ii) Dental formula of mammals is ICPM=2023 ̸ 1023. The numerator tells about the total number of teeth in one side of the upper jaw whereas the denominator tells about the total number of teeth in one side of the lower jaw. It tells that there are 2 Incisors 0 canines 2 premolars 3 molars in the upper jaw as per numerator whereas 1 incisors 0 canines 2 premolar and 3 molar are found in the lower jaw as per denominator. The teeth missing here are canines which are found in between the incisors and premolar. Therefore the correct answer is B Canines

Note: Wisdom or third molar teeth are the last teeth which develop at the age of 18 to 20 in humans. These teeth cause crowding and need to be removed. There are many problems which occur in the teeth of humans like plaque, cavities etc.