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NCERT Exemplar Class 12 Biology Solutions Chapter 3 Human Reproduction: The chapter provides an in-depth understanding of human reproduction, covering all the important topics, starting from gametogenesis to parturition. This chapter is important for students preparing for board exams and medical entrance exams. The exemplar solutions include well-structured answers along with diagrammatic explanations. The answers are designed to improve conceptual clarity and problem-solving skills. The NCERT exemplar solutions provide a variety of objective-type questions and their answers to test the application of concepts in real-life scenarios.
Studying the MCQs regularly enhances analytical thinking and accuracy exams by consistently working through these resources. Students can ensure a strong understanding of Human Reproduction, and improve their overall biology scores. These exemplar solutions give an extra edge to the students while attempting the problems given in the NCERT Class 12 Biology Book.
The solved exemplar questions are given below-
Question:1
Answer:
Pituitary gonadotropins (FSH and LH) play a very vital role during the follicular and ovulatory phases of the menstrual cycle.
Question:2
Meiotic division during oogenesis is different from that in spermatogenesis. Explain how and why.
Answer:
It is true that the meiotic division during oogenesis is different from that in spermatogenesis. Following are the details about the significant differences between them:
Meiosis resumes only once puberty begins.
Following are some possible reasons for this difference in patterns of oogenesis and spermatogenesis:
Question:3
Answer:
The following figure shows various stages of zygote development till implantation:
(a) The zygote divides into a two-cell stage called cleavage. This development takes place when the zygote is still in the isthmus.
(b) The cleavage undergoes further rounds of mitosis to form 2, 4, 8 and finally 16-celled stage.
These daughter cells are called blastomere.
(c) The 16-celled stage is known as morula.
(d) The morula changes into a blastocyst; with more rounds of meiosis. At this stage, the blastomeres are arranged in an outer layer of cells; called trophoblast and an inner mass of cells.
(e) Implantation to the uterine wall happens at the blastocyst stage.
Question:4
Draw a neat diagram of the female reproductive system and label the parts associated with the following
(a) production of gamete,
(b) site of fertilisation
(c) site of implantation and,
(d) birth canal.
Answer:
Question:5
With a suitable diagram, describe the organisation of the mammary gland.
Answer:
Mammary glands are paired structures which contain glandular tissue and a variable amount of fat.
Question:1
Answer:
Menarche marks the onset of puberty (the beginning of the reproductive phase).
Menopause marks the end of the reproductive phase.
Question:2
a. How many spermatozoa are formed from one secondary spermatocyte?
b. Where does the first cleavage division of the zygote take place?
Answer:
(a) One secondary spermatocyte forms four spermatids, all of which subsequently develop into spermatozoa via the process of spermiogenesis.
(b) The first cleavage division of the zygote takes place in the ampullary-isthmus junction.
Question:4
Answer:
Corpus luteum is responsible for the secretion of progesterone, which is essential to maintain the endometrium and helps in the proper development of the foetus.
This is the reason for the long life of Corpus luteum when Fertilisation has occurred. However, when there is no fertilisation, it serves no purpose and thus remains active only for 10-12 days
Question:4
What is the foetal ejection reflex? Explain how it leads to parturition.
Answer:
The foetal ejection reflex is the mild uterine contraction at the time of childbirth. It triggers the release of oxytocin from the maternal pituitary, which induces strong uterine contraction and finally leads to parturition.
Question:5
Except for the endocrine function, what are the other functions of the placenta?
Answer:
The placenta is responsible for the following in addition to its endocrine function –
(A) Supply of oxygen and nutrients to foetus
(B) Removal of waste products from the foetus
Question:6
Why do doctors recommend breastfeeding during the initial period of infant growth?
Answer:
Milk produced during the initial few days of lactation is known as colostrum and contains several antibodies, which are important for the development of disease resistance in the baby. This is the prime reason why doctors recommend breastfeeding during the initial period of growth of an infant.
Question:7
Answer:
During the follicular phase of the menstrual cycle, the following things happen in the ovary and the uterus –
Question:8
Answer:
Hormones responsible for various changes during the menstrual cycle are:
Question:10
Answer:
Following changes occur in the oogonia during the transition of a primary follicle to a Graafian follicle:
(a) Each primary oocyte is surrounded by a layer of granulosa cells; called a primary follicle
(b) Primary follicle transforms into secondary follicle by getting surrounded by another layer of granulosa cells and a new theca.
(c) The secondary follicle then transforms into the tertiary follicle. The tertiary follicle is characterised by a fluid-filled cavity called the antrum. At this stage, the primary oocyte undergoes a second meiotic division and forms a secondary oocyte and a tiny polar body.
(d) The tertiary follicle then changes into a mature Graafian follicle. During this stage, a new layer; called zona pellucida; develops around the secondary oocyte.
Question:1
Answer:
Gametogenesis→Insemination→Fertilization→Implantation→Gestation→Parturition
Question:3
What is the role of the cervix in the human female reproductive system
Answer:
The cervix and vagina together form the birth canal. Parturition happens through the birth canal.
Question:4
Why are menstrual cycles absent during pregnancy?
Answer:
Gonadotropins, which are required for the development of new follicles, are suppressed due to the high levels of progesterone and estrogen during pregnancy. This inhibits the initiation of a new menstrual cycle.
Question:5
Column A | Column B |
Ovaries Oviduct B Vagina | Ovulation A Pregnancy Birth |
Answer:
A. Fertilisation
B. Uterus
Question:6
Answer:
Parturition signals arise from the foetus. Oxytocin is the main hormone involved in parturition and is released from the maternal pituitary gland.
Question:7
What is the significance of epididymis in male fertility?
Answer:
Secretions from the epididymis, vas deferens, prostate and seminal vesicle are essential for the maturation and motility of sperms. These organs play an important role in male fertility.
Question:8
Answer:
Hormone | Function | Hormone’s origin |
Gonadotropin-releasing hormone (GnRH) | Act on the anterior pituitary gland and stimulates the release of LH and FSH | Hypothalamus |
Luteinizing Hormone (LH) | Acts at Leydig cells and stimulates the secretion of androgen | Pituitary |
Follicle Stimulating Hormone (FSH) | Acts on Sertoli cells and stimulates factors which are involved in spermatogenesis | Pituitary |
Question:10
Answer:
Chromosome number reduces to half in gametes as, during gametogenesis, meiosis takes place resulting in the haploid number of chromosomes.
During Fertilisation, male and female gametes undergo fusion to make the diploid zygote.
Question:11
What is the difference between a primary oocyte and a secondary oocyte?
Answer:
Primary Oocyte | Secondary Oocyte |
The primary oocyte is formed when the female is still in the womb | A secondary oocyte is formed when the individual undergoes puberty |
It is surrounded by a secondary follicle | It is surrounded by tertiary follicle |
The number of chromosomes is 46 | The number of chromosomes is 23 |
Question:12
What is the significance of ampullary-isthmic junction in the female reproductive tract?
Answer:
The first cleavage division of the zygote occurs in the ampullary-isthmic junction in the female reproductive tract
Question:13
How does zona pellucida of ovum help in preventing polyspermy?
Answer:
Zona pellucida’s membrane undergoes changes when sperm comes into contact with it. This prevents the entry of other sperm into the ovum and thus prevents polyspermy.
Question:14
Mention the importance of LH surge during the menstrual cycle.
Answer:
The rupture of the Graafian follicle is induced by a rapid surge in LH level. Resulting in the release of ovum (ovulation)
Question:15
Which type of cell division forms spermatids from the secondary spermatocytes?
Answer:
Meiosis results in the formation of spermatids from secondary spermatocytes.
Question:1
Choose the incorrect statement from the following:
a. In birds and mammals, internal Fertilisation takes place
b. Colostrum contains antibodies and nutrients
c. Polyspermy in mammals is prevented by the chemical changes in the egg surfaced.
d. In the human female implantation occurs almost seven days after Fertilisation
Answer:
The answer is option (c) Polyspermy in mammals is prevented by the chemical changes in the egg surface
Explanation: Zona pellucida absorbs water and swells preventing further entry of sperms. So, physical change rather than chemical change is responsible for the prevention of polyspermy in mammals.
Question:2
Identify the correct statement from the following:
a. High levels of estrogen trigger the ovulatory surge.
b. Oogonial cells start to proliferate and give rise to functional ova in regular cycles from puberty onwards.
c. Sperms released from seminiferous tubules are highly motile.
d. Progesterone level is high during the post-ovulatory phase of the menstrual cycle
Answer:
The answer is option (d) Progesterone level is high during the post-ovulatory phase of the menstrual cycle
Explanation: Ovulatory surge is triggered by the high levels of LH and FSH. Sperms released from seminiferous tubules are non-motile. Oogonial cells stop their activity when the girl child is still in the womb.
Question:3
Spot the odd one out from the following structures with reference to the male reproductive system:
a. Rete testis
b. Epididymis
c. Vasa efferentia
d. Isthmus
Answer:
The answer is the option (d) Isthmus
Explanation: The Isthmus is a part of the oviduct in the female reproductive system. Others are parts of the male reproductive system
Question:4
Seminal plasma, the fluid part of semen, is contributed by.
i. Seminal vesicle
ii. Prostate gland
iii. Urethra
iv. Bulbourethral gland
(a) i and ii (b) i, ii and iv (c) ii, iii and iv (d) i and iv
Answer:
The answer is the option (b) (i), (ii) and (iv)
Explanation: Urethra has no contribution to seminal plasma
Question:5
Spermiation is the process of the release of sperm from:
a. Seminiferous tubules
b. Vas deferens
c. Epididymis
d. Prostate gland
Answer:
The answer is the option (a) Seminiferous tubules
Explanation: Seminiferous tubules
Question:6
A mature Graafian follicle is generally present in the ovary of a healthy human female around:
a. 5 – 8 day of menstrual cycle
b. 11 – 17 days of the menstrual cycle
c. 18 – 23 days of menstrual cycle
d. 24 – 28 days of the menstrual cycle
Answer:
The answer is the option (b) 11-17 day of the menstrual cycle
Explanation: After rupturing in the Graafian follicle, ovulation takes place in this period
Question:7
The acrosomal reaction of the sperm occurs due to:
a. Its contact with zona pellucida of the ova
b. Reactions within the uterine environment of the female
c. Reactions within the epididymal environment of the male
d. Androgens produced in the uterus
Answer:
The answer is the option (a) Its contact with zona pellucida of the ova
Explanation: Sperm can enter the ova only after the enzyme from the acrosome breaks down the zona pellucida
Question:8
Which one of the following is not a male accessory gland?
a. Seminal vesicle
b. Ampulla
c. Prostate
d. Bulbourethral gland
Answer:
The answer is the option (b) Ampulla
Explanation: Ampulla is part of the fallopian tube
Question:9
The spermatogonia undergo division to produce sperm by the process of spermatogenesis. Choose the correct one with reference to athe bove.
a. Spermatogonia have 46 chromosomes and always undergo meiotic cell division
b. Primary spermatocytes divide by mitotic cell division
c. Secondary spermatocytes have 23 chromosomes and undergo second meiotic division
d. Spermatozoa are transformed into spermatids
Answer:
The answer is option (c) Secondary spermatocytes have 23 chromosomes and undergo second meiotic division
Explanation: Spermatogonia have 46 chromosomes, and they undergo meiotic cell division; primary spermatocytes undergo meiotic cell division. Spertamids and transformed into spermatozoa
Question:10
Column I A. Head B. Middle piece C. Acrosome D. Tail | Column II i. Enzymes ii. Sperm motility iii. Energy iv. Genetic material |
a. A-ii, B-iv, C-i, D-iii
b. A-iv, B-iii, C-i, D-ii
c. A-iv, B-i, C-ii, D-iii
d. A-ii, B-i, C-iii, D-iv
Answer:
The answer is the option (b) (A) – (iv), (B) – (iii), (C) – (i), (D) – (ii)
Explanation: The nucleus is present in the head. Acrosome releases enzyme which dissolves zona pellucida. The tail helps in the swimming of sperm and the middle piece is the place where mitochondria are present
Question:12
Match the following and choose the correct options:
Column I A. Trophoblast B. Cleavage C. Inner cell mass D. Implantation | Column II i. Embedding of the blastocyst in the endometrium ii. Group of cells that would differentiate as embryo iii. The outer layer of the blastocyst attached to the endometrium iv. Mitotic division of the zygote |
a. A-ii, B-i, C-iii, D-iv
b. A-iii, B-iv, C-ii, D-i
c. A-iii, B-i, C-ii, D-iv
d. A-ii, B-iv, C-iii, D-i
Answer:
The answer is the option (b) (A)-(iii), (B)-(iv), (C)-(ii), (D)-(i)
Question:13
Which of the following hormones is not secreted by the human placenta?
a. hCG
b. Estrogens
c. Progesterone
d. LH
Answer:
The answer is the option (d) LH
Explanation: LH (Luteinizing hormone) is secreted by the pituitary gland
Question:14
The vas deferens receives duct from the seminal vesicle and opens into the urethra as:
a. Epididymis
b. Ejaculatory duct
c. Efferent ductule
d. Ureter
Answer:
The answer is the option (b) Ejaculatory duct
Question:15
Urethral meatus refers to the:
a. Urinogenital duct
b. Opening of vas deferens into urethra
c. The external opening of the urinogenital duct
d. Muscles surrounding the urinogenital duct
Answer:
The answer is the option (c) External opening of the urinogenital duct
Explanation: External opening of the urinogenital duct
Question:16
Morula is a developmental stage:
a. Between the zygote and blastocyst
b. Between the blastocyst and gastrula
c. After the implantation
d. Between implantation and parturition
Answer:
The answer is the option (a) between the zygote and blastocyst
Explanation: between the zygote and blastocyst
Question:17
The membranous cover of the ovum at ovulation is:
a. Corona Radiata
b. Zona radiata
c. Zona pellucida
d. Chorion
Answer:
The answer is the option (a) corona radiata
Question:18
Identify the odd one from the following:
a. Labia minora
b. Fimbriae
c. Infundibulum
d. Isthmus
Answer:
The answer is the option (a) Labia Minora
Also, Read NCERT Solution subject-wise
The topics and subtopics of the chapter are given below-
The chapter-wise solutions for all chapters of Class 12 Biology are given below:-
The NCERT Exemplar Solutions for Class 12 Biology provide well-written explanations that are written by subject experts and help the student remember everything with ease. Solving these questions helps to strengthen their understanding and increase their confidence in exams.
NCERT Exemplar Class 12 Solutions Subject Wise:
This chapter explains the process of gametogenesis, fertilisation, further development of the embryo and finally parturition. It explains the male and female reproductive systems, hormonal regulation and how to maintain overall reproductive health. The menstrual cycle is also thoroughly explained in the chapter. Having a detailed understanding of this chapter is required to master reproductive biology and the related medical concepts.
Must Read NCERT Notes subject-wise
The NCERT Exemplar Class 12 Biology Solutions of Human Reproduction thoroughly explains the human reproductive system, including the structure and function of male and female reproductive organs. The chapter covers all the essential processes such as gametogenesis, hormonal regulation, menstrual cycle and embryonic development. The exemplar solutions provide detailed explanations with label diagrams, which make sure a strong conceptual foundation is built. Practising these objective-type questions helps students test their understanding and improve their problem-solving skills. Thus, these questions and answers prove to be excellent study material for both board as well as entrance exam preparation.
Also Check NCERT Books and NCERT Syllabus here
The students can download the solutions in the pdf format by using the webpage to pdf tool available online at free of cost.
The students who are preparing for their board exams or preparing for entrance exams can benefit from this.
The experts use the chapters and also the information that is provided to them along with their practical knowledge.
It provides the students with simple and stepwise answers to the questions present in the textbook will help them in preparing for the examination.
Chapter 3, "Human Reproduction," in the NCERT Exemplar for Class 12 Biology, delves into the intricacies of human reproduction, covering the male and female reproductive systems, gametogenesis, fertilization, pregnancy, and reproductive health.
The placenta's primary function in human reproduction is to facilitate the exchange of nutrients and oxygen from the mother to the developing fetus, while also removing waste products from the fetus, all while acting as a temporary endocrine organ that produces hormones essential for pregnancy.
Spermatogenesis produces four motile sperm from one diploid cell, while oogenesis produces one non-motile egg (ovum) and three polar bodies from a single diploid cell, with oogenesis also occurring in the ovaries while spermatogenesis occurs in the testes.
Human embryonic development, also known as embryogenesis, encompasses several key stages: fertilization, cleavage, blastocyst formation, implantation, gastrulation, and organogenesis, ultimately leading to the formation of a fetus.
The menstrual cycle is regulated by a complex interplay of hormones, starting with the hypothalamus, which releases GnRH, stimulating the pituitary gland to release FSH and LH, which in turn influence the ovaries and uterus.
In human reproduction, key hormones like estrogen, progesterone, and testosterone, along with follicle-stimulating hormone (FSH) and luteinizing hormone (LH), regulate puberty, fertility, and sexual development, while others like prolactin and oxytocin play roles in childbirth and lactation.
Fertilization and implantation are crucial for reproduction, as fertilization creates a zygote (a single-celled embryo) and implantation allows the embryo to attach to the uterine wall, initiating pregnancy and providing nourishment for development.
NCERT Exemplar questions are crucial for Class 12 Biology exam preparation as they provide a higher level of practice and deeper understanding of concepts, helping students excel in both board and competitive exams.
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