Question

In mammals, the teeth are
(i) Of different types
(ii) Embedded in the cup-like socket of the jaw bones
(iii) Only two sets, present throughout life
These conditions are referred as
(A) Heterodont, thecodont and diphyodont
(B) Thecodont, heterodont and diphyodont
(C) Diphyodont, thecodont and heterodont
(D) Heterodont, diphyodont and thecodont
(E) Thecodont, diphyodont and heterodont

Answer 1

Hint: The alimentary canal starts with a mouth that is anteriorly situated and opens outside through the anus that is posteriorly situated. The mouth further leads to buccal cavity or oral cavity. The oral cavity has a number of teeth and a muscular organ.

Complete answer:
The arrangement of teeth in each half of the upper and lower jaw in the order I, C, PM and M is represented by a dental formula. The dental formula of human beings is $\dfrac{{2123}}{{2123}} \times 2 = 32$.
The hard chewing surface covering of the teeth is made up of enamel which helps in the mastication of food. This enamel is the hardest substance of the human body, secreted by ameloblast cell (ectodermal in origin)
Each tooth has three parts, namely crown, neck and root. Crown remains capped with hard enamel, formed principally of calcium phosphate; it forms the chewing surface of the tooth.
Both crown and root are composed of dentine, secreted by odontoblast cells (mesodermal in origin), inside which a central pulp cavity is present in which there is nerve and blood supply.
Now lets us see what type of dentition is present in mammals.
(i) Of different types : An adult human has 32 permanent teeth which are of four different types, namely incisors (I) canine (C premolars (PM) and molars (M). Such type of dentition is called Heterodont dentition
Embedded in the cup-like socket of the jaw bones : Each tooth is embedded in a socket of jaw bone. This type of teeth attachment is called thecodont
(ii) Only two sets, present throughout life : Majority of mammals including human beings, have two sets of teeth during their life, i.e., one temporary set and one permanent set. A set of temporary milk or deciduous teeth replaced by a set of permanent or adult teeth. Such type of dentition is called diphyodont.

Our required option is A. Heterodont, thecodont and diphyodont.

Note:
Humans have bunodont teeth also. They are small, blunt and have rounded cusps. When teeth are attached to the free surface or summit of the jaw bone they are called acrodont teeth. They are seen in fishes, amphibians and reptiles.