Animal Kingdom Question 847
Question: Assertion : Enamel is present only in vertebrate teeth. Reason : Enamel is secreted by the ectoderm.
Options:
A) If both the assertion and the reason are true and the reason is a correct explanation of the assertion
B) If both the assertion and reason are true but the reason is not a correct explanation of the assertion
C) If the assertion is true but the reason is false
D) If the assertion is false but reason is true
Show Answer
Answer:
Correct Answer: D
Solution:
Enamel is present not only in vertebrate teeth, but also in placoid scales of pisces also.
In Scoliodon the exoskeleton comprises the placoid scales.
A group of cells collect in the dermis to form a dermal papilla.
The dermal papilla grows upwards pushing the epidermis.
The odontoblast present in dermal papilla secrets dentine which becomes calcified.
The Malpighian layers of the epidermis is contact with the dermal papilla is known as enamel organ, the enamel organ brings about formation of vitrodentine over the dentine of the spine.
Placoid scales are the fore-runners of vertebrate teeth, because the two have essentially the same form and structure.
BETA
