Extra Questions for Class 12 Biology Chapter 3 Human Reproduction
Q.1. Name the important mammary gland secretions that help in resistance of the new born baby.
Ans. Colostrum
Q.2. Males in whom testes fail to descend to the scrotum are generally infertile. Why?
Ans. If the testes fail to descend to the scrotum, gametogenesis could be inhibited. The process of spermatogenesis requires a marginally lesser (2°C less) ambient temperature than that in the
abdominal cavity.
Q.3. When do the oogenesis and the spermatogenesis initiate in human females and males respectively?
Ans. Oogenesis in human females initiate at the foetal/embryonic stage.
Spermatogenesis in human males starts at puberty.
Q.4. Mention the location and the function of Leydig cells in humans.
Ans. Leydig cells are present in the regions called interstitial spaces outside the seminiferous tubules.
They synthesise and secrete androgens (testosterone).
Q.5. The path of sperm transport is given below. Provide the missing steps in blank boxes.
Ans. Vasa efferentia, Vas deferens.
Q.6. What is the role of cervix of the human female system in reproduction?
Ans. Cervix helps in regulating the passage of sperms into the uterus and forms the birth canal to
facilitate parturition.
Q.7. Write the location and function of the Sertoli cells in humans.
Ans. Sertoli cells are present in seminiferous tubules. They provide nutrition to the germ cells or sperms.
Q.8. Name the hormones produced only during pregnancy in a human female. Mention their source organ.
Ans. During pregnancy, placenta produces hormones like human chorionic gonadotropin and human placental lactogen and ovary produces relaxin.
Q.9. Mention the function of mitochondria in sperm.
Ans. Provide energy for the movement of sperm tail.
Q.10. How is the entry of only one sperm and not many ensured into an ovum during fertilisation in humans?
Ans. During fertilisation a sperm head comes in contact with zona pellucida layer of ovum and induces changes in the membrane that block the entry of additional sperms.
Q.11. Female reproductive organs and associated functions are given below in column A and B. Fill in the blank boxes.
Ans. A—Fertilisation B—Uterus
Q.12. Name the embryonic stage that gets implanted in the uterine wall of a human female.
Ans. Blastocyst/blastula.
Q.13. Explain the function of umbilical cord.
Ans. Umbilical cord transports nutrients and respiratory gases and metabolic wastes to and from mother and foetus.
Q.14. Mention the function of trophoblast in human embryo.
Ans. Trophoblast is the outer layer of blastocyst which helps in the attachment of blastocyst to the endometrium of the uterus.
Q.15. What is corona radiata?
Ans. The follicle cells that envelope the egg outside zona pellucida are called corona radiata.
Q.16. Identify the figure given below and the part labelled “A”.
Ans. The figure is of blastula/blastocyst.
A—Trophoblast.
Q.17. What name is given to the cells of inner cell mass, that have the potential to give rise to all tissues and organs in a human being?
Ans. Stem cells
Q.18. List the changes that the primary ooctye undergoes in the tertiary follicular stage in the human ovary.
Ans. The primary oocyte within the tertiary follicle grows in size and completes its first meiotic
division to form secondary oocyte and first polar body.
Q.19. Given below are the stages in human reproduction. Write them in correct sequential order.
Insemination, Gametogenesis, Fertilisation, Parturition, Gestation, Implantation
Ans. Gametogenesis, Insemination, Fertilisation, Implantation, Gestation, Parturition.
Q.20. Which part of the blastula is destined to form the germ layers of the developing embryo in humans?
Ans. Inner cell mass