Class 12 Biology Chapter 3 Human Reproduction The answer to each chapter is provided in the list so that you can easily browse through different chapters Assam Board HS 2nd Year Biology Chapter 3 Human Reproduction Question Answer.
Class 12 Biology Chapter 3 Human Reproduction
Also, you can read the SCERT book online in these sections Solutions by Expert Teachers as per SCERT (CBSE) Book guidelines. These solutions are part of SCERT All Subject Solutions. Here we have given Assam Board Class 12 Biology Chapter 3 Human Reproduction Solutions for All Subjects, You can practice these here.
(E) Short Answer Question (Three Marks Each):
Q.1. Describe the male accessory duct system of human.
Ans :The male sex accessory ducts include : Rate testes, vasa efferentia, epididymis and vas deferences. The seminiferous tubules of the testis open into the vasa efferentia through the rate testes. The vasa efferentia leave the testis and open into epididymis located along the posterior surface of each testis. The epididymis leads to vas deference that ascends to the abdomen and loops over the urinary bladder. It receives a from seminal vesicle and opens into urethra as the ejaculatory duct which store and transport the sperms from the testes to the outside through urethra. The urethra originates from the urinary bladder extends through the penis to its external opening called urethral meatus.
Q.2. Draw and label the internal structure of the seminiferous tubules.
Ans :
Q.3. Draw and label the sectional view of the female reproductive system.
Ans :
Q.4. Write a note on the layers of tissues of the wall of the uterus.
Ans : The wall of the uterus has three layers of tissue. The external thr membranous layer is called perinectrium. The middle thick layer of smoot muscle is known as myometrium that exhibits strong contraction during delivery of the baby. The inner glandular layer is called endometrium which line the uterine cavity. The endometrium undergoes cyclical change during menstrual cycle.
Q.5. Draw a neat labeled diagram of a human sperm.
Ans :
Q.6. Distinguish between spermatogenesis and oogenesis.
Ans :
| Spermatogenesis | Oogenesis | ||
| (i) | The process of formation of a male gamete is called spermatogenesis. | (i) | The process of formation of a female gamete is known as oogenesis. |
| (ii) | It occurs in the ovary. | (ii) | It Occurs in the Ovary. |
| (iii) | It starts at puberty. embryonic development. | (iii) | It is started during the. |
| (iv) | No polar body is formed, instead 4 sperms are formed 3 polar bodies are formed. | (iv) | Polar body is formed during oogenesis. Generally |
Q.7. Diagrammatically represents the various events of menstrual cycle.
Ans :
Q.8. Discuss the events of fertilization in man.
Ans : The process of fusion of a sperm with an ovum is called fertilization. During fertilization, at first a sperm comes in contact with the zone pellucida layer of the ovum and induces changes in the membrane that block the entry of additional sperms. Thus it ensures that only one sperm can fertilize an ovum. The secretion of the acrosome help the sperm enter into the cytoplasm of the ovum through the zona pellucida and the plasma membrane and this induces completion of meiotic division results in the formation of haploid ovum. After this the haploid nucleus of the and the ovum fuse together to form zygote.
| Sl. No. | CONTENTS |
| Chapter 1 | Reproduction in Organisms |
| Chapter 2 | Sexual Reproduction in Flowering Plants |
| Chapter 3 | Human Reproduction |
| Chapter 4 | Reproductive Health |
| Chapter 5 | Principles of Inheritance and Variation |
| Chapter 6 | Molecular Basis of Inheritance |
| Chapter 7 | Evolution |
| Chapter 8 | Human Health and Disease |
| Chapter 9 | Strategies for Enhancement in Food Production |
| Chapter 10 | Microbes in Human Welfare |
| Chapter 11 | Biotechnology: Principles And Processes |
| Chapter 12 | Biotechnology and its Applications |
| Chapter 13 | Organisms and Populations |
| Chapter 14 | Ecosystem |
| Chapter 15 | Biodiversity and Conservation |
| Chapter 16 | Bioresources of Assam |
| Chapter 17 | Environmental Issues |
Q.9. State how sex of human is determined?
Ans : The sex of human can be determined in the zygotic stage itself. The chromosome pattern in the human female is XX and that in the male is XY. Therefore, all the haploid gametes produced by the female (ova) have the sex chromosome X whereas in the male gametes (sperms) the sex chromosome could be either X or Y. So 50% of the sperms carry A chromosome while other 50% carry the Y. After fusion the zygote many carry either XX or XY depending on whether sperms carrying X or Y fertilised the ovum the zygote carrying XX would develop into a female body and XY would form a male. So it can be said that the sex of the body is determined by the father and mother is not responsible for this.
Q.10. Discuss briefly the embryonic development up to blastocyst stage.
Ans : The zygote developed after fertilisation moves through the isthmus of the oviduct and at that time mitotic division starts. This process is known a cleavage. The zygote moves towards the uterus and forms 2, 4, 8, 16 daughter cells called blastomeres. The embryo with 8 to 16 blastomeres is called a morula. The morula continues to divide and transforms into blastocyst as it moves further into the uterus.
Q.11. What is parturition? Discuss the process of parturition in human.
Ans : Vigorous contraction of the uterus at the end of pregnancy causes expulsion or delivery of the foetus. This process of the delivery of the foetus is known as parturition.
Parturition in the pregnant female is induced by a complex neuroendocrine mechanism. The signals for parturition origination from the fully developed fetus and the placenta which induce mild uterine contractions called foetal ejection reflex. This triggers release of oxytocin from the maternal pituitary and this acts causes stronger uterine contractions which in turn further secretion of oxytocın. The stimulatory reflex between the uterine contraction and oxytocin secretion continues resulting in stronger and stronger contraction. This leads to expulsion of the baby out of the uterus through the birth canal known as parturition.
Q.12. “Placenta acts as an endocrine tissue”. Justify.
Ans : Placenta not only facilitate the supply of oxygen and nutrients to the embryo and removal of carbon dioxide and waste or excretory materials produced by the embryo but also acts as an endocrine gland by secreting different types of hormones.
The hormone produced by the placenta are human chorionic gonadotropin (hcG), human placental lactogen (hPL), estrogens, progestogens etc. which helps in the fetal growth and in the maintenance of pregnancy.
Q.13. Discuss the role of hormones in menstrual cycle.
Ans : The hormones play a key role in the menstruation cycle are :
(i) FSH-RF of hypothalamus stimulates the secretion of FSH from the anterior pituitary gland.
(ii) FSH stimulates the changes of primary follicle of the ovary into a graafian follicle.
(iii) Inhibit the secretion of FSH and stimulate the secretion of luteinising hormone (LH) from the anterior pituitary.
(iv) Ovulation is controlled by the increased level of LH in blood.
(v) Decreased the secretion of FSH and LH from anterior pituitary which inhibit the maturation of follicle and ovulation.
(vi) Decrease in the level of progesterone and estrogens in the blood stimulates the hypothalamus and anterior pituitary to release FSH- RF and FSH respectively. FSH starts the follicular phase of next menstrual cycle.
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