CBSE Class 12 Biology HOTs Human Reproduction

Please refer to CBSE Class 12 Biology HOTs Human Reproduction. Download HOTS questions and answers for Class 12 Biology. Read CBSE Class 12 Biology HOTs for Chapter 3 Human Reproduction below and download in pdf. High Order Thinking Skills questions come in exams for Biology in Class 12 and if prepared properly can help you to score more marks. You can refer to more chapter wise Class 12 Biology HOTS Questions with solutions and also get latest topic wise important study material as per NCERT book for Class 12 Biology and all other subjects for free on Studiestoday designed as per latest CBSE, NCERT and KVS syllabus and pattern for Class 12

Chapter 3 Human Reproduction Class 12 Biology HOTS

Class 12 Biology students should refer to the following high order thinking skills questions with answers for Chapter 3 Human Reproduction in Class 12. These HOTS questions with answers for Class 12 Biology will come in exams and help you to score good marks

HOTS Questions Chapter 3 Human Reproduction Class 12 Biology with Answers

Question. The act of procreation in mammals and humans involve some basic steps. Mention them in a sequence?
Answer. Insemination, fertilization, embryogenesis, implantation, development, parturition.

Question. Testis / Ovary are called as primary reproductive organs while all the associated ducts and glands come under secondary organs. Give justification for it?
Answer. Reproduction involves sex cells, so the organs that generate the sex cells are called as primary organs while all others will be called as secondary.

Question. Testis like ovary develop within the pelvic cavity, but in the later part of the development testis descend out of the abdominal cavity . What could be the reason for it?
Answer. Spermatogenesis – Required temperature is app.350 C, which can be maintained if they descend out.

Question. The generating tissue must be accompanied by nursing tissue also. Elaborate this statement with respect to human testis?
Answer. Testis – generating tissue- Generative layer of seminiferous tubule. Nursing tissue – Sertoli cells.

Question. Spermatogenesis is a continuous process but its release is not. How reproductive system does manage this situation?
Answer. Sperms need to be stored in epididymus till they are to be released.
 

Question. Based on the above question, explain that under what physiological conditions are the sperms managed and what changes are brought before their release?
Answer. While storing sperms are kept in deactivated stage. The secretions of the glands contain fructose, ions, activation principles that restore the agility and activity.
 

Question. Penis is considered to be a secondary sex organ; still its tube is called as urino-genital canal. Give reason for this consideration?
Answer. The canal within the penis is common between urinary and genital systems.
 

Question. Penis consists of soft tissue and this condition is of no use for insemination. How is this problem overcome during the reproductive physiology?
Answer. Penis –soft tissue has spongy, vascular tissue which gets filled with blood and thereby generates hydrostatic pressure for erection.
 

Question. The spermatozoas need to be activated for bringing out the act of fertilization. What role does accessory sex glands play in this process?
Answer. Accessory glands release fructose, ions, and activation principles.
 

Question. Ovaries are made of soft tissue and are not fixed in any bony socket but are placed in abdominal cavity. So there is a possibility that they may get displaced. But this generally does not happen. How is this attained?
Answer. Ovaries do not normally get displaced due to attached on the mesenteries within the abdominal cavity.
 

Question. There is no direct connection between ovary and fallopian tube, so there is possibility that the ovum may be released within the abdominal cavity, but it does not happen. How does a fallopian tube prevent this situation?
Answer. Fallopian funnel have fimbriated margins that develop a funneling effect to entrap the released ovum.
 

Question. Vagina has dual role in the female reproductive system, both being very crucial in their aspect. If any one of them fails then the very purpose of the system fails. Explain the statement with proper justification?
Answer. Vagina: - a) Insemination- the start of reproduction acts.
b) Birth canal – the culmination of the gestation period.
 

Question. Uterus has three layers with each performing its specific function. What is the role of middle and inner layers and which hormones influence their functioning?
Answer. Uterus: Middle layer- Myometrium- muscles for ejection reflux, Inner layer- Endometrium – Implantation and placenta formation.
 

Question. “Presence of hymen is the indication of virginity, while its absence means the reverse." Discuss the authensity of the statement in the light of modern understanding of the reproductive physiology?
Answer. Hymen can break naturally also due to any physical activity.
 

Question. Once the breast is emptied of the milk, the milk is being produced continuously but it is not being released simultaneously. Secondly the rate of sucking of milk is more than the rate of its production. What does this tells you about the availability of the stocks of milk?
Answer. Milk production is continuous process; it is being stored in the alveolus tissue for use when required.
 

Question. Starting with gameto-gonia ( spermato-gonia and oo-gonia) and ending into sperma-tid and oo-tid, represent the formation of haploid sex cells. Then what is the specific need of morphogenesis and that also in only one of them. Elaborate the statement with proper justification?
Answer. Spermatid and Ootid are nearly spherical. Spermatid needs to undergo morphogenesis and develop a tail so that it can swim through the genital tract to reach the ovum.
 

Question. Seminiferous tubules are the factories for the generation of spermatozoas, but they can’t work on their own. What stimulus do they get? Is the stimulus generated within the tubule or some where else?
Answer. Hormonal stimulus – obtained from pituitary gland .
 

Question. Spermatogenesis and spermeiogenesis are two different processes but both are essential for male reproductive system. How do they differ from each other?
Answer. Spermatogenesis is spermatogonia to spermatid, but spermeiogenesis is from spermatid to spermatozoa.
 

Question. A sperm after being released in the vagina must reach the end of the fallopian tube to participate in the act of fertilization. What machinery comes into play for the said purpose?
Answer. Sperm has to move so tail is required, mitochondria for energy generation, source of energy comes from the secretions.
 

Question. Do LH and FSH have the same function in the male and female reproductive physiology? Justify your answer.
Answer. LH in male stimulate Leidig cells to release androgens, but in females result in ovulation. FSH in males stimulates sertoli cells to release factors for spermeiogenesis but in females it stimulates a new follicle.
 

Question. For completing the act of fertilization the sperm must fuse with the ovum, but the latter is surrounded by lot of extra follicular cells. How the sperm does manage to fuse with the ovum?
Answer. Sperm acrosome release sperm lysins which digest the additional layers around the ovum.
 

Question. Fertilization requires one male and one female gamete, but there are approximately 200 million sperms in a single ejaculation. How then the female reproductive system and the ovum ensure monospermy?
Answer. Touching of the sperm at the right position on the ovum initiates a reaction that blocks the penetration of any further sperm thus polyspermy prevented.
 

Question. The days of the menstrual cycle start with the onset of menses rather than with the end of menses. Give your justification for such a calculation?
Answer. Day 01 starts with the start of menses as a new follicle gets stimulated i.e. a new cycle starts.
 

Question. “Nothing goes waste in the living system. Prove this statement with the help of the different stages of the Graffian follicle in the ovary?
Answer. Graffian follicle releases ovum and gets converted into Corpus luteum (release progesterone) and at the end of gestation period release Relaxin hormone.
 

Question. Spermatogenesis when started gets completed in a single sequence, but oogenesis stops at secondary oocyte stage. The process starts again with fertilization. Why it stops first and then what happens during fertilization act that the oocyte regains its activity?
Answer. Secondary oocyte requires a centriole to complete second stage of meiosis; it gets it from the sperm after fertilization.
 

Question. The size of single celled haploid ovum is same to the single celled but diploid zygote and its size is same to the multicellular morula till it is in the fallopian tube. Give the reason behind this observation?
Answer. Dimension of fallopian tube is narrow, so multiplication occours without increase in the volume of the cells of the embryo.
 

Question. Placenta is an intimate connection between maternal and foetal tissues. It is a dual organ. Justify?
Answer. Placenta- attachment, transport route and endocrine gland.
 

Question.Placenta is not just a connection and umbilical cord is not just a tube. They remain active throughout the gestation period. Is the above statement true? Justify.
Answer. Both remain active through gestation period for the maintenance of pregnancy by physical and hormonal level.
 

Question. “After birth” is not the name of any proceeding to be executed after the birth of a baby, it is some thing else. Elaborate on the authenticity of the statement?
Answer. After birth- the materials that are dislodged and expelled out of the uterus after the expulsion of baby.
 

Question. The dimensions of the fully formed foetus are more than that of the birth canal. How the baby does makes its way out and what role does uterus plays in it?
Answer. Vagina relaxes and pubic symphasis relaxes to widen the canal, uterine muscles contract to generate pressure for expulsion.
 

Question. The milk produced by the mother for the first few days is important for the baby not only energetically but also for some other reason. Elaborate on this statement?
Answer. Colostrum is rich in defence molecules (antibodies) for the baby whose defenses are not mature enough to fight infections.24. Graffian follicle releases ovum and gets converted into Corpus luteum (release progesterone) and at the end of gestation period release Relaxin hormone.
 
 
Important Questions for NCERT Class 12 Biology Human Reproduction
 

Question. About which day in a normal human menstrual cycle does rapid secretion of LH (popularly called LH surge) normally occurs?
(a) 14th day
(b) 20th day
(c) 5th day
(d) 11th day
Answer: A


Question. Which one of the following is the correct matching of the events occurring during menstrual cycle?
(a) Proliferative phase : Rapid regeneration of myometrium and maturation of Graafian follicle
(b) Secretory phase : Development of corpus luteum and increased secretion of progesterone
(c) Menstruation : Breakdown of myometrium and ovum not fertilised
(d) Ovulation : LH and FSH attain peak level and sharp fall in the secretion of progesterone
Answer: B
 

Question. Which one of the following is the most likely root cause why menstruation is not taking place in regularly cycling human female?
(a) Maintenance of the hypertrophical endometrial lining
(b) Maintenance of high concentration of sexhormones in the blood stream
(c) Retention of well-developed corpus luteum
(d) Fertilisation of the ovum 
Answer: B


Question. Which one of the following statements is incorrect about menstruation?
(a) At menopause in the female, there is especially abrupt increase in gonadotropic hormones.
(b) The beginning of the cycle of menstruation is called menarche.
(c) During normal menstruation about 40 mL blood is lost.
(d) The menstrual fluid can easily clot. 
Answer: D


Question. Which part of ovary in mammals acts as an endocrine gland after ovulation?
(a) Stroma
(b) Germinal epithelium
(c) Vitelline membrane
(d) Graafian follicle 
Answer: D


Question. In the human female, menstruation can be deferred by the administration of
(a) combination of FSH and LH
(b) combination of estrogen and progesterone
(c) FSH only
(d) LH only.
Answer: B


Question. Withdrawal of which of the following hormones is the immediate cause of menstruation?
(a) Progesterone
(b) Estrogen
(c) FSH
(d) FSH-RH 
Answer: A


Question. If mammalian ovum fails to get fertilised, which one of the following is unlikely?
(a) Corpus luteum will disintegrate.
(b) Progesterone secretion rapidly declines.
(c) Estrogen secretion further increases.
(d) Primary follicle starts developing. 
Answer: C


Question. Ovulation in the human female normally takes place during the menstrual cycle
(a) at the mid secretory phase
(b) just before the end of the secretory phase
(c) at the beginning of the proliferative phase
(d) at the end of the proliferative phase. 
Answer: D


Question. Which set is similar?
(a) Corpus luteum - Graafian follicles
(b) Sebum - Sweat
(c) Bundle of His - Pacemaker
(d) Vitamin B7 - Niacin 
Answer: A


Question. After ovulation Graafian follicle regresses into
(a) corpus artesia
(b) corpus callosum
(c) corpus luteum
(d) corpus albicans.
Answer: C


Question. In the fertile human female, approximately on which day of the menstrual cycle does ovulation take place?
(a) Day 14
(b) Day 18
(c) Day 1
(d) Day 8 
Answer: A


Question. The mammalian corpus luteum produces
(a) luteotrophic hormone
(b) luteinising hormone
(c) estrogen
(d) progesterone. 
Answer: D


Question. In the 28 day human ovarian cycle, the ovulation takes place typically on
(a) day 14 of the cycle
(b) day 28 of the cycle
(c) day 1 of the cycle
(d) day 5 of the cycle. 
Answer: A


Question. Extrusion of second polar body from egg occurs
(a) simultaneously with first cleavage
(b) after entry of sperm but before fertilisation
(c) after fertilisation
(d) before entry of sperm into ovum.
Answer: B


Question. Capacitation occurs in
(a) epididymis
(b) vas deferens
(c) female reproductive tract
(d) rete testis.
Answer: C


Question. Fertilisation in humans is practically feasible only if
(a) the ovum and sperms are transported simultaneously to ampullary-isthmic junction of the cervix
(b) the sperms are transported into cervix within 48 hrs of release of ovum in uterus
(c) the sperms are transported into vagina just after the release of ovum in fallopian tube
(d) the ovum and sperms are transported simultaneously to ampullary-isthmic junction of the fallopian tube. 
Answer: D


Question. In human females, meiosis-II is not completed until
(a) uterine implantation
(b) birth
(c) puberty
(d) fertilisation. 
Answer: D


Question. Capacitation refers to changes in the
(a) ovum after fertilisation
(b) sperm after fertilisation
(c) sperm before fertilisation
(d) ovum before fertilisation. 
Answer: C


Question. In our society women are blamed for producing female children. Choose the correct answer for the sex-determination in humans.
(a) Due to some defect like aspermia in man.
(b) Due to the genetic make up of the particular sperm which fertilises the egg.
(c) Due to the genetic make up of the egg.
(d) Due to some defect in the women.
Answer: B


Question. Identify the human developmental stage shown as well as the related right place of its occurrence in a normal pregnant woman and select the right option for the two, together.
Develo pmental stage Site of occurrence
(a) Late morula – Middle part of Fallopian tube
(b) Blastula – End part of Fallopian tube
(c) Blastocyst – Uterine wall
(d) 8-celled morula – Starting point of Fallopian tube
Answer: C

Question. Name the hormones involved in the regulation of spermatogenesis.
(a) LH and FSH
(b) Testosterone only
(c) Testosterone and LH
(d) LH only
Answer : A


Question. Read the following statements.
I. Androgens are produced by Sertoli cells.
II. Presence or absence of hymen is not a reliable indicator of virginity or sexual experience.
III. Leydig cells synthesise androgens.
IV. Oogenesis takes place in corpus luteum.
Identify whether the given above statements are true or false.
     I II III IV
(a) T F F T
(b) T F T F
(c) F T T F
(d) F F T T
Answer : C


Question. How many eggs do you think would have been released by human ovary if the mother gave birth to identical twins?
(a) One, fertilised by two sperms
(b) Two, fertilised by different sperms
(c) One, fertilised by single sperm
(d) Two, fertilised by single sperm
Answer : C


Question. How many eggs do you think were released by the ovary of a female dog which gave birth to 6 puppies?
(a) One
(b) Three
(c) Six
(d) Indefinite
Answer : C


Question. 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 : D


Question. The vasa deferens receives duct from the seminal vesicle and opens into urethra as
(a) epididymis
(b) ejaculatory duct
(c) efferent ductule
(d) ureter
Answer : B


Question. Urethral meatus refers to the
(a) urinogenital duct
(b) opening of vas deferens into urethra
(c) external opening of the urinogenital duct
(d) muscles surrounding the urinogenital duct
Answer : C


Question. 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 : B


Question. Which one of the following is not a male accessory gland?
(a) Seminal vesicle
(b) Mammary gland
(c) Prostate
(d) Bulbourethral gland
Answer : B


Question. Mature Graafian follicle is generally present in the ovary of a healthy human female around
(a) 5-8 days of menstrual cycle
(b) 11-17 days of menstrual cycle
(c) 18-23 days of menstrual cycle
(d) 24-28 days of menstrual cycle
Answer : B


Question. Spermiation is the process of the release of sperms from
(a) seminiferous tubules
(b) vas deferens
(c) epididymis
(d) prostate gland
Answer : A


Question. 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 : A


Question. Which of the following hormones is not secreted by human placenta?
(a) hCG
(b) Oestrogens
(c) Progesterone
(d) LH
Answer : D


Question. 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 : A


Question. 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 on the egg surface
(d) In the human female, implantation occurs almost seven days after fertilisation
Answer : B


Question. Identify the correct statement from the following.
(a) High levels of oestrogen triggers 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 menstrual cycle
Answer : B


Question. The spermatogonia undergo division to produce sperms by the process of spermatogenesis.
Choose the correct one with reference to above.
(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 : D


Question. Which among the following has 23 chromosomes?
(a) Spermatogonia
(b) Zygote
(c) Secondary oocyte
(d) Oogonia
Answer : C


Question. The membranous cover of the ovum at ovulation is
(a) corona radiata
(b) zona radiata
(c) zona pellucida
(d) chorion
Answer : A


Question. Identify the odd one from the following.
(a) Labia minora
(b) Fimbriae
(c) Infundibulum
(d) Isthmus
Answer : A

 

Assertion and Reason

In each of the following questions, a statement of Assertion (A) is given and followed by corresponding statement of Reason (R). Of the statements, mark the correct answer as
(a) If both A and R are true and R is the correct explanation of the A
(b) If both A and R are true, but R is not the correct explanation of the A
(c) If A is true, but R is false
(d) If A is false, but R is true

Question. Assertion (A) Production of FSH and LH increases in the ovulation phase.
Reason (R) Due to decrease in the level of LH ovulation (releasing of ova) takes place.
Answer : C


Question. Assertion (A) Progesterone is essential for maintenance of the endometrium.
Reason (R) Endometrium is essential for implantation of fertilised ovum.
Answer : B


Question. Assertion (A) Not all copulations lead to pregnancy.
Reason (R) Fertilisation can only occur if the ovum and sperms are transported simultaneously to the ampullary-isthmic junction.
Answer : A


Question. Assertion (A) In humans, the gamete contributed by the male determines whether the child produced will be male or female.
Reason (R) Sex in humans is a polygenic trait,depending upon a cumulative effect of some genes on X-chromosome.
Answer : C


Question. Assertion (A) Placenta is an endocrine gland.
Reason (R) It secretes many hormones essential for pregnancy.
Answer : B


Question. Assertion (A) The bulbourethral gland is a male accessory gland.
Reason (R) Its secretion helps in the lubrication of the penis, thereby facilitating reproduction.
Answer : A


Question. Assertion (A) Fimbriae are finger-like projections of infundibulum part of oviduct which is closest to ovary.
Reason (R) They are important for the collection of ovum after ovulation from ovary.
Answer : B

 

Statement Based Questions

Question. Read the following statements.
I. The uterus is present in single pair and is also called womb.
II. The shape of uterus is like an inverted pear.
III. The uterus opens into vagina through a narrow cervix.
IV. Birth canal is formed by cervical canal and vagina.
V. Perimetrium of uterus wall is external and thick, myometriumis middle thin layer of smooth muscles and endometrium is inner glandular layer.
Which of the above statements are correct ?
(a) I, II and III
(b) II, III and IV
(c) IV and V
(d) I and V
Answer : B


Question. Read the following statements.
I. Spermatogonia and spermatids are diploid.
II. The extrusion of second polar body from nucleus occurs after the entry of sperm and completion of fertilisation.
III. Spermatogenesis and sperm differentiation under the control of FSH and testosterone.
IV. Achange in ovum after penetration of sperm the formation of second polar body.
V. The secondary oocyte in the Graaffian follicle forms a new membrane called zona pellucida surrounding it.
Which of the above statements are correct?
(a) I, II, III and V
(b) I and III
(c) Only III
(d) II, III, IV and V
Answer : D


Question. Read the following statements.
I. Each testis has about 25 compartments called testicular lobules.
II. Each testicular lobule contains one to three highly coiled seminiferous tubules in which sperms are produced.
III. Sertoli cells act as nurse cells of testicles.
IV. Sertoli cells are activated byFSH secreted by the adenohypophysis.
Which of the above statements are incorrect?
(a) I and III
(b) Only I
(c) II and IV
(d) III and IV
Answer : B


Question. Which of the following statement/s is not correct?
(a) The external opening of penis is called urethral meatus
(b) Glans penis is covered by loose fold of skin called foreskin
(c) Secretion of bulbourethral gland helps in lubrication of penis
(d) None of the above
Answer : D


Question. Which of the following statement is false for uterus?
(a) It is also called womb and its shape is like an inverted pear
(b) It is supported by ligaments attached to the pelvic wall
(c) It opens into oviducts through cervix whose cavity is called cervical canal
(d) It is bound by three layers, outer perimetrium, middle myometrium and inner endometrium
Answer : C


Question. Which one of the following statement is false in respect of viability of mammalian sperm?
(a) Sperm is viable for only up to 24 hrs
(b) Survival of sperm depends on the pH of the medium and is more active in alkaline medium
(c) Viability of sperm is determined by its motility
(d) Sperms must be concentrated in a thick suspension
Answer : A


Question. Which of the following statement is not correct for oogonia?
(a) They are million gamete mother cells
(b) They are formed within each foetal ovary
(c) They are formed throughout the life of female
(d) They start division and get arrested at prophase-I of meiotic division
Answer : C


Question. Given below are four statements (I-IV) regarding embryonic development in humans.
I. Cleavage divisions bring about considerable increase in the mass of protoplasm.
II. With more cleavage divisions, the resultant blastomeres become smaller and smaller.
III. The blastomeres in the blastocyst are arranged into two layers, i.e. trophoblast and endometrium.
IV. Cleavage divisions result in a solid ball of cells called morula.
Which of the above two statements are correct?
(a) I and III
(b) II and IV
(c) I and II
(d) III and IV
Answer : B


Question. Read the given statements and select the correct option.
I. The production of sperms and ovum by the testis in males and the ovaries in female, respectively, called gametogenesis.
II. Each spermatogonium in seminiferous tubule is diploid and contains 46 chromosomes.
(a) Both statements are incorrect
(b) Statement I is correct, but statement II is incorrect
(c) Both statements are correct
(d) Statement I is incorrect, but statement II is correct.
Answer : C


Question. Select the incorrect statement. 
(a) LH and FSH trigger ovulation in ovary
(b) LH and FSH decrease gradually during the follicular phase
(c) LH triggers secretion of androgens from the Leydig cells
(d) FSH stimulates the Sertoli cells which help in spermiogenesis
Answer : B


Question. Identify the correct statement(s) for placenta.
(a) It facilitates the supply of O 2 and nutrients to embryo
(b) It is connected to embryo through umbilical cord
(c) It removes CO2 and excretory material produced by embryo
(d) All of the above
Answer : D


Question. Identify the correct statement on ‘inhibin’. 
(a) It is produced by granulosa cells in ovary and inhibits the secretion of FSH
(b) It is produced by granulosa cells in ovary and inhibits the secretion of LH
(c) It is produced by nurse cells in testes and inhibits the secretion of LH
(d) It inhibits the secretion of LH, FSH and prolactin
Answer : A

 

Question. What lead to menstruation in the absence of fertilisation? 
Answer. In the absence of fertilization, corpus luteum degenerates which causes disintegration of endometrium leading to menstrual cycle.
 

Question. Why not all copulations lead to fertilisation and pregnancy? 
Answer. Reason: fertilisation can only occur if the ovum and sperms are carried simultaneously.
 

Question. A mother gets infected with a virus which causes German measles during pregnancy. Is it possible that the foetus will also get infected? How ? What are its ill-effect on the foetus?` 
Answer. Yes, it is possible that the foetus gets infected. These viruses may diffuse through placenta. It may cause malformations in the developing embryo.
 

Question. How is the action of LH different in male and female? 
Answer. In male, LH is called ICSH (Interstitial cells stimulating hormone) which stimulates the leydig cells of the testis to secrete testosterone. In females, LH promotes ovulation and controls the formation of corpus luteum after ovulation.
 

Question. Study the figure given below and answer the question that follow:
CBSE_Class_12_Biology_Human_Reproduction_1
a) Identify 'a' in the figure and mention its function.
b) Mention the stage of human embryo it follows.
c) Where are the stem cells located in this embryo?
d) Which part of this stage of human embryo gets attached to endometrium to establish pregnancy? 
Answer.
a) Inner cell mass.it forms the tissues of future embryo.
b) Morula.
c) In the inner cell mass.
d) The pole of the blastocyst that contains the inner cell mass. 
 
Question.  The following illustration is the sequence of oogenesis in human female:
CBSE_Class_12_Biology_Human_Reproduction_2
a) Mention the chromosome no. in a primary oocyte and a secondary oocyte respectively.
b) When is meiosis II completed in the oogenesis of human female?
c) At what stage is meiosis I suspended in a primary oocyte? 
Answer.
a) Primary oocyte=46; secondary oocyte=23.
b) It is completed during fertilisation.
c) Prophase I.
 
 
 
Important Questions for NCERT Class 12 Biology Human Reproduction
 

Question. What happens during fertilisation in humans after many sperms reach close to the ovum?
(a) Secretions of acrosome helps one sperm enter cytoplasm of ovum through zona pellucida.
(b) All sperms except the one nearest to the ovum lose their tails.
(c) Cells of corona radiata trap all the sperms except one.
(d) Only two sperms nearest the ovum penetrate zona pellucida. 
Answer: A


Question. The second maturation division of the mammalian ovum occurs
(a) shortly after ovulation before the ovum makes entry into the fallopian tube
(b) until after the ovum has been penetrated by a sperm
(c) until the nucleus of the sperm has fused with that of the ovum
(d) in the Graafian follicle following the first maturation division. 
Answer: B


Question. Which one of the following statements about morula in humans is correct?
(a) It has almost equal quantity of cytoplasm as an uncleaved zygote but much more DNA.
(b) It has far less cytoplasm as well as less DNA than in an uncleaved zygote.
(c) It has more or less equal quantity of cytoplasm and DNA as in uncleaved zygote.
(d) It has more cytoplasm and more DNA than an uncleaved zygote. 
Answer: A


Question. In human female, the blastocyst
(a) forms placenta even before implantation
(b) gets implanted into uterus 3 days after ovulation
(c) gets nutrition from uterine endometrial secretion only after implantation
(d) gets implanted in endometrium by the trophoblast cells. 
Answer: D


Question. A change in the amount of yolk and its distribution in the egg will affect
(a) pattern of cleavage
(b) number of blastomeres produced
(c) fertilisation
(d) formation of zygote. 
Answer: A


Question. Grey crescent is the area
(a) at the point of entry of sperm into ovum
(b) just opposite to the site of entry of sperm into ovum
(c) at the animal pole
(d) at the vegetal pole. 
Answer: B


Question. What is true for cleavage?
(a) Size of embryo increases
(b) Size of cells decreases
(c) Size of cells increases
(d) Size of embryo decreases 
Answer: B


Question. Blastopore is the pore of
(a) archenteron
(b) blastocoel
(c) coelom
(d) alimentary canal.
Answer: A


Question. Fertilizin is a chemical substance produced from
(a) polar bodies
(b) middle piece of sperm
(c) mature eggs
(d) acrosome. 
Answer: C


Question. In human beings, the eggs are
(a) mesolecithal
(b) alecithal
(c) microlecithal
(d) macrolecithal. 
Answer: B


Question. In an egg, the type of cleavage is determined by
(a) the amount and distribution of yolk
(b) the number of egg membranes
(c) the shape and size of the sperm
(d) the size and location of the nucleus. 
Answer: A


Question. What is true about cleavage in the fertilised egg in humans?
(a) It starts while the egg is in fallopian tube.
(b) It starts when the egg reaches uterus.
(c) It is meroblastic.
(d) It is identical to the normal mitosis. 
Answer: A


Question. Termination of gastrulation is indicated by
(a) obliteration of blastocoel
(b) obliteration of archenteron
(c) closure of blastopore
(d) closure of neural tube. 
Answer: A


Question. In telolecithal egg the yolk is found
(a) all over the egg
(b) on one side
(c) both the sides
(d) centre. 
Answer: B


Question. Acrosome reaction in sperm is triggered by
(a) capacitation
(b) release of lysin
(c) influx of Na+
(d) release of fertilizin.
Answer: C


Question. Meroblastic cleavage is a division which is
(a) horizontal
(b) partial/parietal
(c) total
(d) spiral. 
Answer: B


Question. Blastopore is
(a) opening of neural tube
(b) opening of gastrocoel
(c) future anterior end of embryo
(d) found in blastula.
Answer: B


Question. During cleavage, what is true about cells?
(a) Nucleocytoplasmic ratio remains unchanged.
(b) Size does not increase.
(c) There is less consumption of oxygen.
(d) The division is like meiosis. 
Answer: B


Question. Freshly released human egg has
(a) one Y-chromosome
(b) one X-chromosome
(c) two X-chromosome
(d) one X-chromosome and one Y-chromosome.
Answer: B


Question. Sperm and egg nuclei fuse due to
(a) base pairing of their DNA and RNA
(b) formation of hydrogen bonds
(c) mutual attraction due to differences in electrical charges
(d) attraction of their protoplasts. 
Answer: D


Question. Cells become variable in morphology and function in different regions of the embryo. The process is
(a) differentiation
(b) metamorphosis
(c) organisation
(d) rearrangement.
Answer: A

 

One Mark Questions

Question. Zygote undergoes mitosis to form 16 celled stage of embryo. What is it known as? 
Answer. Morula


Question. Name the important mammary gland secretions that help in resistance of the new born baby. 
Answer. Colostrum


Two mark questions:

1) Fill in the boxes

 

class_12_Biology__Hots_6

Answer.
a) Primary spermatocytes
b) Spermatids


Question. Why does fertilisation take place in fallopian tube and not in uterus? 
Answer.The pH is not suitable for fertilization in uterus.


Question. Which cell organelle is present in the neck of the sperm? What is its significance? 
Answer.Mitochondria It produces energy for the movement of tail that facilitates sperm motility essential for fertilization.


Question. Failure of fertilisation leads to menstruation. Explain. 
Answer.
In the absence of fertilization corpus luteum degenerates. This causes disintegration of endometrium leading to menstruation.

 

Three marks

Question. How does the ovum ensure that only one sperm fertilizes it? 
Answer. During fertilisation a sperm comes in contact with Zona pellucida layer of the ovum & induces change in the membrane that block entry of additional sperms. Thus it ensures single sperm entry.


Question. Name the part of the female reproductive system where the embryo is implanted. Mention the type of tissue by which it is made up of and give their functions? 
Answer.
Uterus Uterus is made of three tissue layers_
a) External thin membranous layer__Perimetrium 
b) Middle thick layer of smooth muscle__Myometrium
c) Inner glandular layer__Endometrium.
Endometrial layer undergoes cyclic changes during menstrual cycle. Myometrium exhibits strong contraction during delivery of the baby.


Question. What is the fate of inner cell mass in the blastocyst? Mention theirsignificance. 
Answer.
The inner cell mass of embryo differentiates into
i) Outer layer----Ectoderm
ii) Inner layer----endoderm
iii) Middle layer----Mesoderm
These three layers give rise to all tissues (organs) in adults.


Question. Label a,b,c in the following diagram. 
Answer.a). Nipple        b). Ampulla        c). Fat

class_12_Biology__Hots_7

 
 
 
 

Five marks Questions

Question. Give the term / reason 
a) Mechanism responsible for parturition.
b) Role of oxytocin during expulsion of the baby out of uterus
c) Why does zona pellucida layer block the entry of additional sperms?
d) Sperm cannot reach ovum without seminal plasma.
e) All copulations do not lead to fertilization and pregnancy.
Answer.
a) complete nuero-endocrine mechanism
b) Oxytocin acts on uterine muscle for stronger contraction
c) To ensure the fusion of one sperm
d) Seminal plasma is a liquid medium which helps the sperm to move & nourishes it.
e) The movement of sperm and ovum does not occur simultaneously many times.
 

Question. Women are often blamed for giving birth to girl child in our society. What is your view? 
Answer.
The belief is totally wrong.
It is the probability of X or Y chromosome combination that decides the sex of the child.
Detail in page 52 of NCERT class xii (sex determination) Chromosome Y decides the sex.
 

Question. Furnish the technical term for the following: 
a) Cushion of fatty tissue covered by skin and pubic hair in female external genitalia.
b) The finger like projections which collect ovum after ovulation
c) The middle thick layer/wall of uterus
d) Semen without sperm
e) The finger-like projections appearing on the trophoblast after implantation.
Answer.
a) Mons pubis
b) Fimbriae
c) Myometrium
d) Seminal plasma
e) Chorionic villi
 
Important Questions for NCERT Class 12 Biology Human Reproduction
 

Question. Which of the following cells during gametogenesis is normally diploid ?
(a) Spermatogonia
(b) Secondary polar body
(c) Primary polar body
(d) Spermatid 
Answer: A


Question. What is the correct sequence of sperm formation?
(a) Spermatogonia, spermatozoa, spermatocytes, spermatids
(b) Spermatogonia, spermatocytes, spermatids, spermatozoa
(c) Spermatids, spermatocytes, spermatogonia, spermatozoa
(d) Spermatogonia, spermatocytes, spermatozoa, spermatids
Answer: B


Question. Which one of the following statements is false in respect of viability of mammalian sperm?
(a) Sperm is viable for only up to 24 hours.
(b) Survival of sperm depends on the pH of the medium and is more active in alkaline medium.
(c) Viability of sperm is determined by its motility.
(d) Sperms must be concentrated in a thick suspension. 
Answer: A


Question. Which one of the following statements about human sperm is correct?
(a) Acrosome has a conical pointed structure used for piercing and penetrating the egg, resulting in fertilisation.
(b) The sperm lysins in the acrosome dissolve the egg envelope facilitating fertilisation.
(c) Acrosome serves as a sensory structure leading the sperm towards the ovum.
(d) Acrosome serves no particular function. 
Answer: B


Question. The correct sequence of spermatogenetic stages leading to the formation of sperms in a mature human testis is
(a) spermatogonia - spermatocyte - spermatid - sperms
(b) spermatid - spermatocyte - spermatogonia - sperms
(c) spermatogonia - spermatid - spermatocyte - sperms
(d) spermatocyte - spermatogonia - spermatid - sperms. 
Answer: A


Question. In humans, at the end of the first meiotic division, the male germ cells differentiate into the
(a) spermatids
(b) spermatogonia
(c) primary spermatocytes
(d) secondary spermatocytes. 
Answer: D


Question. Sertoli cells are regulated by the pituitary hormone known as
(a) LH
(b) FSH
(c) GH
 (d) prolactin. 
Answer: B


Question. The middle piece of the sperm contains
(a) proteins
(b) mitochondria
(c) centriole
(d) nucleus. 
Answer: B


Question. How many sperms are formed from a secondary spermatocyte?
(a) 4
 (b) 8
(c) 2
(d) 1 
Answer: C


Question. Egg is liberated from ovary in
(a) secondary oocyte stage
(b) primary oocyte stage
(c) oogonial stage
(d) mature ovum stage. 
Answer: A


Question. Which of the following hormone levels will cause release of ovum (ovulation) from the Graffian follicle?
(a) High concentration of Estrogen
(b) High concentration of Progesterone
(c) Low concentration of LH
(d) Low concentration of FSH 
Answer: A


Question. No new follicles develop in the luteal phase of the menstrual cycle because
(a) follicles do not remain in the ovary after ovulation
(b) FSH levels are high in the luteal phase
(c) LH levels are high in the luteal phase
(d) both FSH and LH levels are low in the luteal phase. 
Answer: D


Question. Match the items given in column I with those in column II and select the correct option given below.
       Column I                         Column II
A. Proliferative phase      (i) Breakdown of endometrial lining
B. Secretory phase         (ii) Follicular phase
C. Menstruation             (iii) Luteal phase
       A   B   C
(a) (iii) (ii) (i)
(b) (i) (iii) (ii)
(c) (ii) (iii) (i)
(d) (iii) (i) (ii) 
Answer: C


Question. Changes in GnRH pulse frequency in females is controlled by circulating levels of
(a) progesterone only
(b) progesterone and inhibin
(c) estrogen and progesterone
(d) estrogen and inhibin. 
Answer: C


Question. Select the incorrect statement.
(a) LH and FSH decrease gradually during the follicular phase.
(b) LH triggers secretion of androgens from the Leydig cells.
(c) FSH stimulates the Sertoli cells which help in spermiogenesis.
(d) LH triggers ovulation in ovary. 
Answer: A


Question. Identify the correct statement on ‘inhibin’.
(a) Is produced by granulosa cells in ovary and inhibits the secretion of LH
(b) Is produced by nurse cells in testes and inhibits the secretion of LH
(c) Inhibits the secretion of LH, FSH and prolactin
(d) Is produced by granulosa cells in ovary and inhibits the secretion of FSH 
Answer: D


Question. Which of the following events is not associated with ovulation in human female?
(a) Release of secondary oocyte
(b) LH surge
(c) Decrease in estradiol
(d) Full development of Graafian follicle 
Answer: C


Question. The main function of mammalian corpus luteum is to produce
(a) estrogen only
(b) progesterone
(c) human chorionic gonadotropin
(d) relaxin only. 
Answer: B


Question. Menstrual flow occurs due to lack of
(a) oxytocin
(b) vasopressin
(c) progesterone
(d) FSH. 
Answer: C


Question. The secretory phase in the human menstrual cycle is also called
(a) luteal phase and lasts for about 6 days
(b) follicular phase and lasts for about 6 days
(c) luteal phase and lasts for about 13 days
(d) follicular phase and lasts for about 13 days.
Answer: C


ONE MARK QUESTIONS:

1. Production of sperms requires low temperature. How is it accomplished in human body?

2. How many sperms are approximately present in an ejaculate of human male? What proportion of them should have normal size and shape?

3. What is the number of chromosomes in the following cells of human male?
a) Spermatids b) Sertoli cells

4. A spermatogonial cell has 30 chromosomes. How many chromosomes will be formed in a) The primary spermatocyte b) a spermatid derived from the cell?

5. Why is cleavage in a mammalian zygote referred to as holoblastic?

6. How many autosomes and allosomes are found in a single matured human sperm?

7. Name the developmental stage in humans which gets implanted in uterine wall?

8. Why is colostrum essential for an infant?

9. Sometimes the doctor injects some medicine into the body of a woman to induce uterine contractions and delivery. What do you think that the doctor has injected?

10. Not all copulations result in pregnancy. Give a reason.

TWO MARKS QUESTIONS:

1. Suppose the acrosome of mammalian spermatozoa does not function normally, how would it affect fertilization? Give reasons.

2. .An ovum allows the entry of only one sperm at a time. Why?

3. Blood of mother never mixes up with that of foetus. Yet it nourishes the foetus. How?

4. What is gynaecomastia? What is its cause during neonatal period?
(Hint: Klinefelters syndrome)

5. Explain why there is no menstrual cycle before puberty, after menopause and during pregnancy.

THREE MARKS QUESTIONS

1. The events of the menstrual cycle are represented below. Answer the questions following the diagram 
cbse-class-12-biology-hots-human-reproduction
a. State the levels of FSH, LH and progesterone simply by mentioning high or low around 13th, 14th day and 21st to 23rd day.
b. In which of the above mentioned phases does the egg travel to the fallopian tube?

2. Given below is an incomplete flow chart showing influence of hormones on gametogenesis in males. Observe the flow chart carefully and fill in the blanks A, B and C. 
cbse-class-12-biology-hots-human-reproduction

3. a) In which part of human female reproductive system do the following events take place?
i. Release of 1st polar body
ii. Release of 2nd polar body
iii. Fertilization
iv. Implantation
b) From where do the signals for parturition originate and what does maternal pituitary release for simulating uterine contraction for child birth?

FIVE MARKS QUESTIONS

1. Study the following diagram and answer the following questions: 
cbse-class-12-biology-hots-human-reproduction
a) Label the parts A,B,C,D,E and F
b) How does D differ from F?
c) What is the function of E?

2. Study the diagram and answer questions that follows: 
cbse-class-12-biology-hots-human-reproduction
a. What is the role of corpus luteum in menstrual cycle?
b. Why is luteal phase otherwise called as secretory phase?
c. How is estrogen related to menstrual cycle?
d. How does FSH and LH regulate the menstrual cycle?

Chapter 01 Reproduction in Organisms
CBSE Class 12 Biology HOTs Reproduction In Organisms
Chapter 02 Sexual Reproduction In Flowering Plants
CBSE Class 12 Biology HOTs Sexual Reproduction In Flowering Plants
Chapter 03 Human Reproduction
CBSE Class 12 Biology HOTs Human Reproduction
Chapter 04 Reproductive Health
CBSE Class 12 Biology HOTs Reproductive Health
Chapter 05 Principles of Inheritance and Variation
CBSE Class 12 Biology HOTs Principles Of Inheritance And Variation
Chapter 06 Molecular Basis of Inheritance
CBSE Class 12 Biology HOTs Molecular Basis of Inheritance
Chapter 07 Evolution
CBSE Class 12 Biology HOTs Evolution
Chapter 08 Human Health and Disease
CBSE Class 12 Biology HOTs Human Health and Disease
Chapter 09 Strategies for Enhancement In Food Production
CBSE Class 12 Biology HOTs Strategies For Enhancement In food Production
Chapter 10 Microbes In Human Welfare
CBSE Class 12 Biology HOTs Microbes In Human Welfare
Chapter 11 Biotechnology Principles and Processes
CBSE Class 12 Biology HOTs Biotechnology Principles and Processes
Chapter 12 Biotechnology and Its Application
CBSE Class 12 Biology HOTs Biotechnology And Its Applications
Chapter 13 Organisms and Populations
CBSE Class 12 Biology HOTs Organism And Population
Chapter 14 Ecosystem
CBSE Class 12 Biology HOTs Ecosystem
Chapter 15 Biodiversity and Conservation
CBSE Class 12 Biology HOTs Biodiversity And Conservation
Chapter 16 Environmental Issues
CBSE Class 12 Biology HOTs Environmental Issues
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CBSE Class 12 Biology HOTs All Chapters Set A
CBSE Class 12 Biology HOTs All Chapters Set B
CBSE Class 12 Biology HOTs Answers to HOTs Questions Database
CBSE Class 12 Biology HOTs Biodiversity
CBSE Class 12 Biology HOTs Biodiversity Set A
CBSE Class 12 Biology HOTs Biology in Human Welfare
CBSE Class 12 Biology HOTs Ecology
CBSE Class 12 Biology HOTs Genetics and Evolution
CBSE Class 12 Biology HOTs Organisms And Environment
CBSE Class 12 Biology HOTs Reproduction
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HOTS for Chapter 3 Human Reproduction Biology Class 12

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