Question

Which dental formula represents a heterodont in placental draught and tough animals?
A)L3/3​, C1/1​, PM4/4​, M3/2​
B)L3/3​, C1/1​, PM2/3​, M1/1​
C)L1/2​, C0/0​, PM2/3​, M3/3​
D)L3/3​, C1/1​, PM4/4​, M3/3​

Answer 1

Hint: Teeth are vital to an animal as they're used for eating, grooming and defense. Mammals have teeth of various sizes and shapes, a condition called heterodonty, allowing different teeth to be specialized for various tasks. These include:
1.Incisors (I)
2.Canine teeth (C)
3.Premolars (P)
4.Molars (M)

Complete answer:
Mammals even have two sets of teeth: a deciduous set (milk teeth, baby teeth) and a permanent set. All mammals, and some non-mammalian vertebrates have thecodont dentition (teeth are set in sockets within the jaw bone). Most fish, amphibians, and reptiles have their teeth either resting on the surface of the jaw bone (acrodont dentition), or more broadly attached to the jaw on its rim and inner wall (pleurodont dentition). Non-mammalian vertebrates are typically homodont, meaning that each one of the teeth are of the identical shape, as in sharks and crocodiles. Mammals are typically heterodont. The form of the teeth in mammals usually matches the food they eat. This implies that they need a range of tooth shapes. Most mammals have incisors, canines, premolars, and molars.

Early appearances of the heterodont tooth condition are found in fossil varieties of early mammals. The triconodont cheek teeth appeared in a number of the earliest prototherian mammals. A triconodont tooth had three points set in a very line. Later prototherians had the tri tuberculate tooth shape, with the cusps or points offset from each other and interlocking with the cusps of the opposing jaw.
The dental formula of a mammal lists the amount of every of the tooth types, incisors, canines, premolars, and molars, from one side of the maxilla, above an identical list from the mandibula.

Dental Formulae
Dental formulas indicate the quantity of every kind of tooth for a given species. Because the jaw is bilaterally symmetrical, just one half the jaw is described. The incisors are indicated first, followed by the canine, premolars and molars. The maxillary arcade or upper jawbone is listed over the mandibular arcade or submaxilla.
Heterodonty indicates that there are tooth shape differences along the tooth row—incisors and canines rostrally and cheek teeth (premolars and molars) caudally.
Incisors and canines are fairly consistent in shape among mammals. The incisors of rodents are unique in that they grow continually. Also rodents and lots of other herbivores lack canines and even some premolars. The premolars of some carnivores are modified for cutting meat from the bones of prey. This shearing tooth shape is understood as secodont.

Molars of most mammals are of a kind called bunodont. They need low blunt cusps covered with enamel. The selenodont teeth of ungulates, and also the lophodont teeth of elephants have folds of enamel which run deep within the tooth between areas of the dentin. As these teeth wear they quickly lose the enamel of the surface, but the folds of the enamel persist. The areas of exposed dentin wear away more quickly than the enamel. The surface of the tooth is then left with ridges of enamel separated by grooves of dentin.

Hence, the correct answer is option (D)

Note: Humans and most other mammals are diphyodont, meaning that they grow two sets of teeth. As we age the deciduous teeth (baby teeth, milk teeth) are lost and replaced with permanent teeth. Some mammals are considered toothless because they lack permanent teeth. A number of these species do grow deciduous teeth in infancy, but loose them as they mature. These species are sometimes cited as monophyodont. Most other vertebrates are polyphyodont. They lose teeth and replace them repeatedly throughout their life.