This set of Class 12 Biology Chapter 3 Multiple Choice Questions & Answers (MCQs) focuses on “Human Reproduction – Structure of a Sperm”.
1. The body of sperm is covered by _______
b) cell membrane
c) cell wall
Explanation: As in the case of any other cell, sperms are enveloped by a phospholipid bilayer, which is also called as plasma membrane or cell membrane.
2. What part of sperm holds the haploid chromatin?
Explanation: Sperm can be divided into 4 parts namely: head, neck, middle piece and tail. The haploid nucleus is present in the head. Acrosome is the cap-like structure of head which helps it to fertilize the ovum.
3. Egg is covered by a tough sheet of tissue that protects it from desiccation and infection by pathogens. But the same tissue also prevents sperm nuclei from encountering the egg nuclei. However, a part of sperm is known to release enzymes that digest this tough sheet. What part of sperm is it?
a) Tail end
d) Sperm nuclei
Explanation: Acrosome is the cap-like structure present on the anterior-most end of the sperm head. It is filled with numerous enzymes like hyaluronic acid which are released upon encounter of egg in female oviduct. These enzymes function by digesting the membrane, thus allowing penetration of head and further release of male nuclei.
4. Rakesh and Reshma have difficulty conceiving a baby. They consulted a sex therapist. Sperm count of Rakesh was normal but the doctor observed that the motility of his sperm was less. What part of sperm do you think has the issue?
Explanation: Mitochondria are present in the middle piece of the sperm. They are essential for producing energy required for movement of tail. This is essential for movement through the genital tract and oviduct before sperm encounters the egg. Rakesh might have less or poorly functional mitochondria, which prevent his normal count of sperms from moving along the genital tract.
5. Which of the following is not an essential feature of sperms that determine the fertility of a male?
a) Sperm count
b) Sperm motility
c) Sperm height
d) Sperm production rate
Explanation: Sperm count is essential as it determines the probability of a sperm encountering the egg. Sperm motility is essential to ensure the passage of sperms through the genital tract, uterus and oviduct. Sperm production rate determines the number of healthy coitus a male can have. Sperm height is not a determining factor of fertility.
6. Sperms are produced in _______
a) vas deferens
b) vasa efferentia
c) rete testis
d) seminiferous tubules
Explanation: Seminiferous tubules are lined by spermatogonia and Sertoli cells. Spermatogonia undergo meiosis to produce sperm that are nourished by Sertoli cells.
7. What is the consequence of low sperm count?
Explanation: Low sperm count leads to lesser amount of sperms entering the genital tract and passing successfully before encountering the egg in the oviduct. Thus less sperm count leads to lesser chances of fertilization and might result in infertility.
8. The major constituents of semen are _____ and _____
a) Sperms and RBCs
b) Sperms and Blood plasma
c) Sperms and seminal plasma
d) Sperms and WBCs
Explanation: Sperms are released out from seminiferous tubules facilitated by seminal plasma composed of secretions from epididymis, vas deferens, seminal vesicle, and prostate.
9. What doesn’t constitute to the seminal plasma?
a) Secretion of epididymis
b) Secretion of vas deferens
c) Secretion of vas efferens
d) Secretion of seminal vesicle
Explanation: Seminal plasma helps in the motility and maturation of sperm. Secretions produce it from vas deferens, epididymis, seminal vesicle and prostate.
10. What is not a function of the male sex hormone Testosterone?
a) Onset of spermatogenesis
b) Maintenance of accessory ducts
c) Release of semen
d) Maintenance of accessory glands
Explanation: Testosterone secreted by Leydig cells stimulates spermatogenesis. It also acts on accessory ducts and glands and maintains their proper function. Release of sperms and semen is not coordinated by testosterone.
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