Question

Assertion: It is generally monospermy in most animals
Reason: Vitelline membrane of ovum checks polyspermy.
A. Both assertion and reason are true and the reason is the correct explanation of the assertion
B. Both assertion and reason are true but the reason is not the correct explanation of the assertion
C. The assertion is true but the reason is false
D. Both assertion and reason are false
E. The assertion is false but the reason is true.

Answer 1

Hint: The union of male and female gametes (sperm and ovum respectively) fused within the fallopian tube of the human female body takes place, this process is called fertilization. Fertilization leads to the formation of zygote. Fertilization involves four stages, named preparation of sperm, recognition, and binding of sperm-egg, a fusion of male and female gametes, and zygote formation.

Complete answer:
The phenomenon which involves fertilization of one ovum by a single sperm results in the formation of a zygote with two copies of chromosomes is called monospermy. After fertilization, a membrane is formed to prevent the entry of other sperms. It is common in most animals.
The phenomenon which involves the fertilization of a single ovum by more than one sperm leads to the formation of a zygotic cell which comprises more than two copies of chromosomes is called polyspermy.
Human fertilization rarely involves polyspermy. The prevention of polyspermy includes two steps, named Fast block polyspermy and slow block polyspermy.
Vitelline membrane or zona pellucida comprises a thick matrix that surrounds the egg. When fertilization takes place, sperm penetrates the ovum through the Vitelline membrane. After fertilization, zona pellucida thickens up which leads to the entry of multiple sperm.

Note: In monospermy zygote carries one chromosome from a female gamete and another from a male gamete. Polyspermy forms the zygote that carries one chromosome from the female parent and the other from the multiple sperms. Polyspermy possesses a harmful effect on species formation. Due to carrying more than two copies of chromosomes, zygote forms from the polyspermy shows unnatural deletion chromosomes.