CHAPTER-3: HUMAN REPRODUCTION

MCQ Class 12 Biology

CHAPTER-3: HUMAN REPRODUCTION
MCQ Class 12 Biology

Question 1. Ovulation in the human female normally takes place during the menstrual cycle

(a) at the mind secretory phase

(b) just before the end of the secretory phase

(d) at the end of the proliferative phase.

Question 2. After ovulation Graafian follicle regresses into

(a) corpus atresia (b) corpus callosum

Question 3. Immediately after ovulation, the mammalian egg is covered by a membrane known as

(a) chorion (b) zona pellucida (c) corona radiate (d) vitelline membrane.

Question 4. Which one of the following events is correctly matched with the time period in a normal menstrual cycle ?

(a) Release of egg : 5 th day (b) Endometrium regenerates : 5 – 10 days

(d) Rise in progesterone level : 1 – 15 days

Question 5.If mammalian ovum fails to get fertilised, which one of the following is unlikely ?

(a) Corpus luteum will distintegrate. (b) Progesterone secretion rapidly declines.

Question 6. A human female reaches menopause aroung the age of

(a) 50 years (b) 15 years (c) 70 years (d) 25 years.

Question 7. A reaction of granules content which harden the zona pellucida and ensures sure block to polyspermy is

(a) acrosomal reaction (b) cortical reaction (c) acrosin reaction (d) bindin reaction.

Question 8. Which part of the sperm plays an important role in penetrating the egg membrane?

(a) Allosome (b) Tail (c) Autosome

(d) Acrosome

Question 9. In oocyte secondary maturation occurs in

(a) ovary (b) abdominal cavity (c) Fallopian tube (d) uterus.

Question 10. Besides activating the egg another role of a sperm is to carry to egg

(a)RNA (b) mitochondria (c)DNA (d) ribosome:

Question 11. Preparation of sperm before penetration of ovum is

(a) spermiation (b) cortical reaction (c) spermiogenesis (d) capacitation.

Question 12 Spermiation is the process of the release of sperms from

(a) seminiferous (b) vas deferens (c) epididymis (d) prostate gland

Question 13. 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 day of menstrual cycle

Question 14. Acrosomal reaction of the sperm occurs due to

(a) its contact with zona pellucida of theova

(b) reactions within the uterine environment of the female

(d) androgens produced in the uterus.

Question 15. Which one of the following is not a male accessory gland ?

(a) Seminal vesicle (b) Ampulla (c) Prostate (d) Bulbourethral gland

Question 16. Which among the following has 23 chromosomes ?

(a) Spermatogonia (b) Zygote (c) Secondary oocyte (d) Oogonia

Question 17. Which of the following hormones is not secreted by human placenta ?

a) hCG (b) Estrogens (c) Progesterone (d) LH

Question 18. The vas deferens receives duct from the seminal vesicle and opens into urethra as

(a) epididymis (b) ejaculatory duct (c) efferent ductile (d) ureter

Question 19. Urethral meatus refers to the-

(a) urinogenital duct (b) opening of vas deferens into urethra

.Question 20. Morula is a developmental stage

(a) between the zygote and blastocyst (b) between the blastocyst and gastrula

Question 21. The membranous cover of the ovum at ovulation is

(a) corona radiata (b) zona radiate (c) zona pellucida (d) chorion.

Question 22. Identify the odd one from the following

(a) Labia minora (b) Fimbriae (c) Infundibulum (d) Isthmus

Question 23. Temperature ofthe scrotum which is necessary for the functioning oftestis is always

around below body temperature.

(a)2°C (b) 4°C (c)6°C (d) 8°C

Question 24. Which of the following is correct about mammalian testes?

(a) Graafian follicles, Sertoli cells, Leydig‘s cells

(b) Graafian follicles, Sertoli cells, Seminiferous tubules

(d) Graafian follicle, leyding‘s cells, Seminiferous tubule

Question 25. The nutritive cells found in seminiferous tubules are

(a) Leydig‘s cells (b) atretic follicular cells (c) Sertoli cells (d) chromaffin cells.

Question 26. Sertoli cells are regulated by the pituitary hormone known as

(a) LH (b) FSH (c) GH (d) prolactin.

Question 27. The head of the epididymis at the head of the testis is called

(a) cauda epididymis b) vas deferens (c) caput epididymis (d) gubernaculum.

Question 28. Seminal plasma in humans is rich in

(a) fructose and calcium but has no enzymes (b) glucose and certain enzymes but has no calcium

Question 29. Prostate glands are located below

(a) gubernaculum (b) seminal vesicles (c) epididymis (d) bulbourethral glands

Question 30. The function of the secretion of prostate gland is to

(a) inhibit sperm activity (b) attract sperms c) stimulate sperm activity(d) none of these.

Question 31. Lower narrow end of uterus is called

(a) urethra (b) cervix (c) clitoris (d) vulva.

Question 32. Bartholin‘s glands are situated

(a) on the either side of vagina in humans (b) on either side of vas deferens in humans

Question 33. In human adult females oxytocin

(a) stimulates pituitary to secrete vasopressin (b) causes strong uterine contractions during parturition

Question 34. The third stage of parturition is called ―after-birth‖. In this stage

(a) excessive bleeding occurs

(b) fetus is bom and cervix and vagina contraction to normal condition happens

(d) placenta is expelled out.

Question 35. After birth, colostrum is released from mammary glands which is rich in

(a) fat and low in proteins (b) proteins and low in fat

Question 36. Spot the odd one out from the following structures with reference to the male reproductive system.

(a) Rate testis (b) Epididymis (c) Vasa efferentia (d) Isthmus

Question 37. Seminal plasma, the fluid part of semen, is contributed by

(i) seminal vesicle (ii) prostate (iii) urethra (iv) bulbourethral gland

a) (i) and (ii) (b) (i), (ii) and (iv) (c) (ii), (iii) and (iv) (d) (i) and (iv)

Question 38.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.

Question 39. How many sperms are formed from a secondary spermatocyte ? (a) 4 (b)8 (c) 2 (d) 1

Question 40. How many sperms are formed from 4 primary spermatocytes ? (a) 4 (b)1 (c) 16 (d) 32

Question 41. In spermatogenesis, reduction division of chromosome occurs during conversion of

(a) spermatogonia to primaryspermatocytes

(b) primary spermatocytes to secondaryspermatocytes

(d) spermatids to sperms.

Question 42. Which of the following groups of cells in the male gonad, represent haploid cells ?

(a) Spermatogonial cells (b) Germinal epithelial cells

Question 43. The process of release of spermatozoa from Sertoli cells into cavity of the seminiferous tubules is called

(a) spermiogenesis (b) spermatogenesis (c) spermatocytogenesis (d) spermiation.

Question 44. The principal tail piece of human sperm shows the microtubular arrangement of

(a) 7+ 2 (b) 9+ 2 (c)11+2 (d) 13 + 2

Question 45. Acrosome is a type of

(a) lysosome (b) flagellum (c) ribosome (d) basal body.

Question 46. Which of the following contains the actual genetic part of a sperm ?

(a) Whole of it (b) Tail (c) Middle piece (d) Head

Question 47. The sperms undergo physiological maturation, acquiring increased motility and fertilizing capacity in

(a) seminiferous tubules (b) vasa efferentia (c) epididymis (d) vagina.

Question 48. At what stage of life is oogenesis initiated in a human female ?

(a) At puberty (b)During menarche (c) During menopause (d) During embryonic development

Question 49. 1st polar body is formed at which stage of oogenesis ?

(a) 1st meiosis (b) 2nd mitosis (c) 1st mitosis (d) Differentiation

Question 50. Which one is released from the ovary ?

(a) Primary oocyte (b) Secondary oocyte (c) Graafian follicle (d) Oogonium

.Question 51. During oogenesis, each diploid cell produces

(a) four functional eggs (b) two functional eggs and two polar bodies

Question 52. In oogenesis haploid egg is fertilised by sperm at which stage ?

(a) Primary oocyte (b) Secondary oocyte (c)Oogonium (d) Ovum

Question 53. Layers of an ovum from outside to inside is

(a) corona radiata, zona pellucida and vitelline membrane

(b) zona pellucida, corona rodiata and vitelline membrane

(d) zona pellucida, vitelline membrane and corona radiata.

Question 54. Which part of ovary in mammals acts as an endocrine gland after ovulation ?

(a) Stroma (b) Germinal epithelium (c) Vitelline membrane (d) Graafian follicle

Question 55. The sex of the fetus will be decided at

(a) fertilisation by male gamete(b) implantation

Question 56. 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.

Question 57. Cleavage differs from mitosis in lacking

(a) synthetic phase (b) growth phase (c) both (a) and (b) (d) none of these.

Question 58. The solid mass of 8-16 cells formed from zygote after successive mitotic divisions is called

(a) blastula (b) gastrula (c)morula (d) none of these.

Question 59.Implantationtakesplaceafter of fertilisation.

(a) 5 days (b) 6 days (c) 7 days (d) 8 days

Question 60. Structure connecting the fetus to placenta is

(a) umbilical cord (b) amnion (c) yolk sac (d) chorion.

Question 61. Which of the following hormones is not a secretory product of human placenta?

(a) Human chorionic gonadotropin (b) Prolactin (c) Estrogen (d) Progesterone

Question 62. Urine test during pregnancy determines the presence of

(a) human chorionic gonadotropin hormone (b) estrogen

Question 63. In the event of pregnancy, the corpus luteum persists under the influence of

(a) LH (b) FSH (c) chorionic gonadotropin (d) progesterone.

Question 64. During the development of embryo, which of the following occurs first?

(a) Differentiation of organ (b) Differentiation oftissue

Question 65. The structures derived from ectoderm are

(i) pituitary gland (ii) cornea (iii) kidneys (iv) notochord

(a) (i) and (iii) (b) (ii) and (iii) (c) (i) and (ii) (d) (ii) and (iv).

Question 66. Gastrula is the embryonic stage in which

(a) cleavage occurs (b) blastocoel form (c) germinal layers form (d) villi form.

Question 67. In the development of the human body, the ectoderm is responsible for the formation of

(a) lens of the eye (b) nervous system (c) sweat glands (d) all of these.

Question 68. The first movements of the fetus and appearance of hair on its head are usually observed during which month of pregnancy?

(a) Fourth month (b) Fifth month (c) Sixth month (d) Third month

Question 69. The early stage human embryo distinctly possesses

(a) gills (b) gill slits (c) external ear (pinna) (d) eyebrows.

Question 70. Delivery of developed fetus is scientifically called

(a) parturition (b) oviposition (c) abortion (d) ovulation.

Assertion Reason

Directions:

In the following questions, a statement of assertion is followed by a statement of reason. Mark the

correct choice as:

(a) If both Assertion and Reason are true and Reason is the correct explanation of Assertion.

(b) If both Assertion and Reason are true but Reason is not the correct explanation of Assertion.

(c) If Assertion is true but Reason is false.

(d) If both Assertion and Reason are false.

1. Assertion: In human male, testes are extraabdominal and lie in scrotal sacs. Reason: Scrotum acts as thermoregulator and keeps testicular temperature lower by 2°C for normal spermatogenesis.

2. Assertion: Testicular lobules are the compartments present in testes.

Reason: These lobules are involved in the process of fertilization.

3. Assertion: Interstitial cell is present in the region outside the seminiferous tubule called interstitial spaces. Reason: Interstitial cells provide nutrition to the sertoli cells.

4. Assertion: The testes are situated outside the abdominal cavity within the scrotum. Reason: Muscles in scrotum helps to maintain low temperature of testes, necessary for spermatogenesis.

5. Assertion: The bulbourethral gland is a male accessory gland.

Reason: Its secretion helps in the lubrication of the penis, thereby facilitating reproduction.

6. Assertion: Each seminiferous tubule is lined on its inside by three type of cells.

Reason: These cells are male germ cells, Sertoli cells and Leydig cells.

7. Assertion: In human male, there are perianal glands near the anus. Reason: Perianal glands secretes sex-attractant pheromone which initiates sexual desire in human.

8. Assertion: Testes are located in the scrotum, outside the coelom.

Reason: A vaginal coelom partly surrounds the testes in the scrotum.

9. Assertion: Fimbriae are finger-like projections of the infundibulum part of oviduct which is closest to ovary.

Reason: They are important for collection of ovum after ovulation from ovary.

10. Assertion: Finger-like projections appear on the trophoblast called chorionic villi after implantation.

Reason: Chorionic villi are surrounded by the uterine tissue and maternal blood.

11. Assertion: Infundibulum is a funnel shaped part closer to ovary.

Reason: The edges of infundibulum helps in collection of the ovum after ovulation.

12. Assertion: The female external genitalia includes mons pubis, labia majora and labia minora. Reason: The glandular tissue of each breast is divided into 5-10 mammary lobes.

13. Assertion: Vagina acts as copulation canal and fertilization canal.

Reason: Both insemination and fusion of gametes occur in the vagina of female.

14. Assertion: In the testis, spermatogenesis occurs in the seminiferous tubules and testosterone secretion takes place from the sertoli cells.

Reason: Testosterone brings growth and maturation of primany sex organs and also development of accessory sex characters.

15. Assertion: Spermatogenesis starts at the age of puberty.

Reason: There is a siginificant increase in level of gonadotropin releasing hormone at puberty.

16. Assertion:Human male ejaculates about 200to 300million sperms during coitus

Reason: Only few reach the isthmus ampullary junction for process of fertilisation.

17. Assertion: The sperm head contains a cap-like structure called acrosome.

Reason: Acrosome is filled with enzymes that help in fertilisation of the ovum.

18. Assertion: A drop in temperature does not affect spermatogenesis. Reason: During temperature drop, the smooth muscles contract and bring the testes closer to the pelvic cavity.

19. Assertion:Thehumanmaleejaculatesabout50-100millionspermsduringa coitus.

Reason: For normal shape and size.

20. Assertion: The type B spermatogonia undergo mitosis to form primary spermatocyte. Reason: Primary spermatocyte completes the first meiotic division leading to secondary spermatocytes.

21. Assertion: The middle piece is called as power house of the sperm. Reason: The numerous mitochondria coiling around axial filament produce energy for the movement of the tail.

22. Assertion: The regions outside the seminiferous tubules are called interstitial spaces, which contain Leydig cell.

Reason: Leydig cells synthesise and secrete testicular hormones called androgens.

23. Assertion: Primary spermatocytes of testes are haploid.

Reason: These are formed by meiosis-I in the spermatogonia.

24. Assertion: Stem cells possess the property of totipotency.

Reason: These cells can give rise to any type of cells.

25. Assertion: At puberty, human male develops secondary sexual characters. Reason: At puberty, there is decreased secretion of testosterone in male.

26. Assertion: Head of sperm consists of acrosome and mitochondria.

Reason: Acrosome contains spiral row of mitochondria.

27. Assertion: In a Graafian follicle, the primary oocyte and the follicular cells may be regarded as sibling cells.

Reason: Both arise from the same parent cell the oogonium by mitotic division.

28. Assertion: The shape of the uterus is like an inverted pear

Reason: The inner glandular layer that lines the uterine cavity is called as myometrium.

29. Assertion: Fallopian funnel of oviduct has finger-like fimbriae.

Reason: Graafian follicle of ovary is with secondary oocyte hanging in cavity called antrum.

30. Assertion: Production of FSH increases, while that of LH decreases in the ovulation phase.

Reason: Due to decrease in the level of LH, ovulation (releasing of ova) takes place.

31. Assertion: Graafian follicle ruptures at the mid of menstrual cycle releasing the ovum.

Reason: Both LH and FSH attain a peak level at the middle of cycle.

32. Assertion: Progesterone is required for maintenance of the endometrium.

Reason: Endometrium is essential for implanation of embryo.

33. Assertion: The endometrium undergoes cyclical changes during menstrual cycle.

Reason: The myometrium exhibits strong contractions during delivery of the baby.

34. Assertion: Menstrual phase is also called shedding tears of lost ovum.

Reason: In the menstrual phase, cast of endometrial lining along with ovum takes place due to reduced titre of oestrogen and progesterone.

35. Assertion : Penetration of sperm into ovum is a chemical process.

Reason : Acrosome of sperm secretes a lytic enzyme hyaluronidase which dissolves vitelline membrane of ovum.

36. Assertion: Size of breasts increases at puberty in human female.

Reason: Prolactin secretion starts at puberty.

37. Assertion: During fertilization only head of spermatozoa enters egg.

Reason: If several spermatozoa hit the egg at same time, all can enter the egg.

38. Assertion: Corpus luteum degenerates in the absence of fertilization.

Reason: Progesterone level decreases.

39. Assertion: Mammalian ova produces hyaluronidase.

Reason: The eggs of mammal are microlecithal and telolecithal.

40. Assertion: Ovum retains most of the contents of the primary oocyte and is much lartger than a spermatozoa.

Reason: Ovum requires energy to go about in search of a spermatozoa for fertilisation.

41. Assertion: Not all copulation leads to pregnancy.

Reason: Fertilisation can only occur if the ovum and sperms are transported simultaneously to the ampullary isthmic junction.

42. Assertion: Implantationis theprocess of attachmentof blastocyston uterine endometrium.

Reason: Implantation is controlled by trophoblast and occurs by decidual cell reaction.

43. Assertion: Placenta is an endocrine gland.

Reason: It secretes many hormones essential for pregnancy.

44. Assertion: A woman passes out hCG in the urine during pregnancy. Reason: The presence of hCG in urine is the basis for pregnancy test.

45. Assertion: Breast feeding during initial period of infant growth is recommended.

Reason: Colostrum contains several antibodies, essential to render immunity in newborns.

46. Assertion: During pregnancy, the levels of hormones like estrogens and progesterone are increased.

Reason: The increased production of these hormones is essential for foetal growth.

47. Assertion: Vigrous contraction of the uterus at the end of pregnancy causes expulsion.

Reason: The stimulatory reflex between the uterine contraction and oxytocin results in

weakening contractions.

48. Assertion: There is generally monospermy in most of animals. Reason: Vitelline membrane of ovum checks polyspermy

49. Assertion: All Metatherian are placental mammals. Reason: All placental mammals have menstrual cycle.

50. Assertion: Placenta in addition to connection with mother and foetus, is a ductless gland. Reason: It releases human gonadotropins.

51. Assertion: Embryonic development proves inter-relationship and common ancestory of metazoans. Reason: It involves similar sequence of five dynamic processes during development

52. Assertion: In morula stage, cells divide without increase in size.

Reason : Zona pellucida remains undivided till cleavage is complete.

53. Assertion: The embryo with 8 to 16 blastomeres is called a morula. Reason: The morula continues to divide and transforms into trophoblast.

54. Assertion: Parturition is induced by neural signal in maternalpituitary.

Reason: At the end of gestation period, the maternal pituitary releases prolactin which causes uterine contractions.

SOLUTION

1. (a) In human male, one pair testes are present in thin walled skin pouches called scrotal sac (so are extra abdominal) hanging from lower abdominal wall between the legs. Scrotal

sac act as thermoregulators and keeps the testicular temperature 2°C lower than body temperature for normal spermatogenesis, as high abdominal temperature kills the

spermatogenic tissue.

2. (d) Testicular lobules are the compartments present in the testes that are not involved in the process of fertilization as whole. Fusion of male and female gametes is called fertilization.

3. (c) Leydig cells, also known as interstitial cells, are found adjacent to the seminiferous tubules in the testicle. They produce testosterone in the presence of luteinizing hormone (LH).

4. (a) The testes are situated outside the abdominal cavity within a pouch called scrotum. The scrotum helps in maintaining low temperature of the testes (2-2.5 °C) lower than the

normal internal body temperature which is necessary for spermatogenesis.

5. (a) Bulbourethral gland, also called Cowper's Gland, either of two pea-shaped glands in the male are located beneath the prostate gland at the beginning of the internal

portion of the penis. These are responsible for adding fluids to semen during the process of ejaculation, thereby facilitating the process of reproduction.

6. (d) Each seminiferous tubule is lined on its inside by two types of cells called male germ cells (spermatogonia) and sertoli cells. The male germ cells undergo meiotic divisions finally

leading to sperm formation, while sertoli cells provide nutrition to the germ cells. The regions outside the seminiferous tubules called interstitial spaces, contain small blood vessels and

interstitial cells or Leydig cells. Leydig cells synthesise and secrete testicular hormones called androgens.

7. (d) Perianal gland are found in rabbit not in human beings. These are a pair of dark elongated scent glands lying behind the cowper‘s glands. These are sex attractant secreting

glands, its smell serves as sex attractant for the female.

8. (c) Vaginal coelom partly surrounds the testes in scrotum in a wrong statement because vagina is the part of external genitalia (vulva) in the female reproductive system and scrotum

is a sac like structure in which testes are suspended.

9. (b) The ends of the fallopian tubes close to the ovaries are covered with finger like projections called fimbriae. Each of these fimbriae are covered with tiny hair like projections

called cilia. When an egg cell is released from the ovary, it is swept into the fallopian tube by the cilia ofthe fimbriae.

10. (b) After implantation, finger-like projections appear on the trophoblast called chorionic villi which are surrounded by the uterine tissue and maternal blood. The chorionic villi and uterine

tissue become interdigitated with each other and jointly form a structural and functional unit between developing embryo (foetus) and maternal body called placenta.

11. (b) In human females, each fallopian tube extends from the periphery of each ovary to the uterus, the part closer to the ovary is the funnel shaped infundibulum. The edges

of the infundibulum possess finger-like projections called fimbriae which help in collection of the ovum after ovulation.

12. (c) The female external genitalia include mons pubis, labia majora, labia minora, hymen and clitoris. Mons pubis is a cushion of fatty tissue covered by skin and pubic hair. The labia majora

are fleshy patches of tissue, which extend down the mons pubis and surrounds the vaginal opening. The labia minora are paired folds of tissue under the labia majora. A functional mammary

gland is characteristic of all female mammals. The mammary glands are paired structures (breasts) that contain glandular tissue and variable amount of fat. The glandular tissue of

each breast is divided into 15-20 mammary lobes containing clusters of cells called alveoli.

13. (d) Vagina is the tubular female copulatory organ. Passageway for menstrual flow as well as birth canal. Vagina receives semen from male during mating but fertilization (fusion of

gametes) occurs in fallopian tube.

14. (d) In the testis, spermatogenesis occurs in the seminiferous tubules and testosterone secretion takes place in the interstitial cells. Testosterone brings growth and maturation of secondary

sex organs. It also brings about development of secondary sex characters.

15. (a) Spermatogenesis starts at the age of puberty due to significant increase in the Gonadotropin Releasing Hormone (GnRH).

16. (a) The male releases large number of sperms inside female reproductive tract to increase chances of fertilisation.

17. (b) Acrosome contains enzymes that help the sperm penetrate the ova during the fertilisation process.

18. (a) The normal temperature of the testes in the scrotum is about 2-2.5 °C lower than the internal body temperature. When the body is chilled, the smooth muscle contracts and

brings the testes closer to the pelvic cavity. This movement towards the pelvic cavity allows the testes to absorb heat from the rest of the body so that the sperrm cells

do not become chilled and get optimum temperature for spermatogenesis.

19. (d) The human male ejaculates about 200 to 300 million sperms during a coitus out of which, at least 60 percent sperms must have normal shape and size and atleast 40 percent of

them must show vigorous motility for normal fertility.

20. (b) Type B spermatogonia undergo mitosis to produce diploid intermediate cells called primary spermatocytes. These cells further undergo first meiotic or reductional division

to give rise to haploid secondary spermatocytes.

21. (a) The middle piece of human contains mitochondria coiled round the axial filament called mitochondrial spiral. They provide energy for the movement of the

sperm. So it is called as the 'power house of the sperm'.

22. (b) Each testicular lobule contains one to three highly coiled seminiferous tubules in which sperms are produced. Each seminiferous tubule is lined on its inside by two types of cells

called male germ cells (spermatogonia) and sertoli cells. The male germ cells undergo meiotic divisions finally leading to sperm formation, while sertoli cells provide nutrition to hte germ

cells. The regions outside the seminiferous tubules called interstitial spaces, contain small blood vessels and interstitial cells or Leydig cells. These cells synthesise and secrete testicular

hormones called androgens.

23. (d) Primary spermatocytes of testes are diploid and formed by mitotic division in the spermatogonium.

24. (a) Stem cells have the property to give rise to any type of cell/tissue.

25. (c) Puberty in human male is controlled by male sex hormone testosterone which is secreted by interstitial or leydig cells of testes. So, secondary sexual characters develop and

at puberty, secretion of testosterone is increased.

26. (c) Head of a sperm has acrosome but the spiral row of mitochondria are present in the mid (connecting) piece of the sperm.

27. (a) Primary oocyte and follicle cells both arise from the Graafian follicle by mitosis cell division. Hence, these are regarded as the sibling cells.

28. (c) The uterus is single and it is also called womb. The shape of the uterus is like an inverted pear. The wall of the uterus has three layers, external thin membranous perimetrium, middle

thick layer of smooth myometrium and inner glandular layer of endometrium.

29. (b) Infundibulum is funnel shaped end of fallopian or oviduct. The funnel is called oviducal funnel or fallopian funnel. Its free174 Assertion Reason Question Bank end bears a number of finger

like processes called fimbriae, but graafian follicle of ovary is with secondary oocyte hanging in cavity, called antrum.

30. (c) In fertility phase/ovulation, production of FSH decrease, while that of LH increases. It causes ovulation. The ovum is drawn into fallopian tube. It is viable for two days when

fertilisation can occur. Ovulation takes place between 10th-14th day. Two characteristics of the fertility phase that help in fertilisation are : (i) Uterine movement help in the spread of sperms in

female reproductive tract. (ii) Ciliary movements in the epithelium of fallopian tubes for bringing in the ovum.

31. (a) Graafian follicle is formed due to increase in FSH and ruptures due to rise in level of LH during middle of menstrual cycle.

32. (b) Progesterone prepares the uterus for pregnancy. After ovulation occurs, the ovaries start to produce progesterone needed by the uterus. Progesterone causes the uterine lining or

endometrium to thicken. This helps to prepare a supportive environment in the uterus for a fertilized egg.

33. (b) The wall of the uterus has three layers of tissue. The external thin membranous perimetrium, middle thick layer of smooth muscle, myometrium and inner glandular layer called

endometrium that lines the uterine cavity. The endometrium undergoes cyclical changes during menstrual cycle while the myometrium exhibits strong contraction

during the delivery of the baby.

34. (a) Menstrual phase is the phase of menstrual flow which continues for 3-5 days and involves discharge of blood along with casting off endometrial lining due to reduced titre

of both estrogen and progesterone. Menstrual phase is also called funeral of unfertilized egg or shedding tears of lost ovum. First day of menstrual phase is also considered to

be first day of menstrual cycle.

35. (a) Penetration of sperm is a chemical mechanism. In this, acrosome of sperm undergoes acrosomal reaction and releases certain sperm lysins, which dissolve the egg locally

and make the path for the penetration of sperm lysins which are acidic proteins. These sperms lysins contain a lysing enzyme hyaluronidase which dissolves the hyaluronic acid polymers in the

intercellular spaces which holds the granulosa cells of corona radiata together; corona penetrating enzyme and acrosin. Then it dissolves the zona pellucida. Only sperm nucleus and middle

piece enters the ovum.

36. (b) In female, breasts size increases after puberty under the stimulation of estrogen. Size of breasts is further increased during pregnancy and after childbirth under the stimulation of

prolactin hormone.

37. (c) During fertilization, only one sperm head enters into ovum and remaining parts of body degenerates. If several spermatozoa hit the egg at same time, even then only one can get entry

into egg because after entry of one sperm, the egg becomes impervious to other sperms.

38. (b) In female, graafian follicle forms corpus luteum after ovulation. The cells of corpus luteum are called luteal cells. The cytoplasm of luteal cells have yellow granules called lutein

which secrete the hormone progesterone to maintain pregnancy if fertilization takes place. In the absence of fertilization, corpus luteum degenerates and forms corpus albicans and there

is decrease in progesterone level as well.

39. (d) Hyaluronidase, a hydrolytic enzyme is an acrosomal content in mammalian sperm. It helps at the time of fertilization during the penetration of the sperm into the ovum.

Based on the amount of yolk, mammalian eggs are alecithal means egg without yolk. Microlecithal eggs contain very little yolk e.g., sea urchin, starfish.On the basis of distribution

of yolk telolecithal eggs are those eggs in which the yolk, is concentrated towards the vegetal pole and cytoplasm and nucleus lie near the animal pole, e.g., birds and reptiles.

40. (c) Sperm needs energy to move about in female tract, so that fertilisation of ova takes place.

41. (a) All copulation do not lead to fertilisation as the synchronisation of sperm and ova reaching the fallopian tube isimportant.

42. (b) The process of attachment of the blastocyst (mammalian blastula) on the endometrium of uterus is called implantation.

43. (b) Placenta is an endocrine gland that is present only during pregnancy. It is responsible for production of various hormones like human Chorionic Gonadotropin (hCG), estrogen,

progesterone, human placental lactogen (hPL).

44. (b) The chorionic cells secrete a hormone called human Chorionic Gonadotropin (hCG), which resembles and takes over the job of pituitary LH during pregnancy. hCG maintains

the corpus luteum and stimulates it to secrete progesterone.

45. (a) Colostrum is rich in antibodies, which is essential for new born babies.

46. (b) During pregnancy, the levels of hormones like estrogen, progestrogens, cortisol, prolactin, thyroxine, etc., are increased several folds in the maternal blood. Increased production of these

hormones is essential for supporting the foetal growth, metabolic changes in the mother and maintenance of pregnancy.

47. (c) Vigorous contraction of the uterus at the end of pregnancy causes parturition. Parturition is induced by a complex neuroendocrine mechanism. The signals for parturition originate from the

fully developed foetus and the placenta which induce mild uterine contractions called foetal ejection reflex.

48. (b) Entrance of a single sperm into an oocyte is called monospermy generally found in most of animals. Cortical granules are extruded in the perivitelline space by exocytosis

and some of these are attached along inner surface of vitelline membrane which now thickens and becomes impervious to any other sperm entry. It is now called fertilization

membrane. It prevents polyspermy.

49. (b) Metatherians are pouched mammals or marsupials, whereas eutherians are placental mammals with well developed placenta

50. (a) Placenta is a ductless endocrine gland which produces various hormones like human Chorionic Gonadotropin (hCG), estrogen, progesterone, human placental lactogen

(hPL).

51. (a) Embryonic development includes a definite series of phases which are fundamentally similar in all sexually reproducing organisms, and transform a one-celled zygote to a multicellular

and fully formed developmental stage till hatching or birth. Such a remarkable similarity of embryonic development proves that all metazoans are interrelated and have common ancestory.

Embryonic development involves five dynamic changes and identifiable processes which are - gametogenesis, fertilization, cleavage, gastrulation and organogenesis.

52. (a) Morula involves cleavage of cells till 32 cell stage is formed. It is still surrounded by zona pellucida.

53. (c) Cleavage starts as the zygote moves through the isthmus of the oviduct 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 furither into the uterus.

54. (d) The process of delivery of foetus (childbirth) is called parturition. Parturition is induced by a complex neuroendocrine mechanism. The signals for parturition originate from the fully

developed foetus and the placenta which induces mild uterine contractions called foetal ejection reflex. This triggers release of oxytocin from the maternal pituitary. Oxytocin acts on the uterine

muscles and causes stronger uterine contractions which in turn stimulate further secretion of oxytocin. The stimulato CASE STUDY BASED QUESTION ry reflex between the uterine contractions and oxytocin secretion continues

resulting in stronger and stronger contractions. This leads to expulsion of the baby out of the uterus through the birth canal.

CASE STUDY BASED QUESTION

The average duration of human pregnancy is about 9 months which is called the gestation period. Vigorous contraction of the uterus at the end of pregnancy causes expulsion / delivery of the

foetus. This process of delivery of the foetus (childbirth) is called parturition. Parturition is induced by a complex neuroendocrine mechanism. The signals for parturition originate from the fully developed

foetus and the placenta which induce mild uterine contractions called foetal ejection reflex. This triggers the release of oxytocin hormone from the maternal pituitary gland. Oxytocin acts on the

uterine muscle and causes stronger uterine contractions, which in turn stimulates further secretion of oxytocin. The stimulatory reflex between the uterine contraction and oxytocin secretion

continues resulting in stronger and stronger contractions. This leads to expulsion of the baby out of the uterus through the birth canal – parturition. Soon after the infant is delivered, the

placenta is also expelled out of the uterus.

i. The birth of a baby is known as

a. Micturition b.Parturition c. Child d. Oxytocin

ii. When a fully developed baby is not naturally delivered by the mother, it could be due to the –

a. Non-secretion of Oxytocin b. Excess secretion of Oxytocin

c. Wide birth canal d. None of the above.

iii. Soon after the infant is delivered, the placenta is also expelled out ofthe uterus, because

a. The infant requires the placenta to be alive

b. After the birth, there is no role for the placenta

c. Placenta is a part of the infant

d. None of the above

iv. Oxytocin is known as the child birth hormone as well as the:

a. Urine regulating hormone b. Milk ejection hormone

c. Milk producing hormone d. None of the above

v. Assertion: Release of oxytocin is essential for the child birth after he complete development of the foetus.

Reason: Premature release of Oxytocin leads to the birth of a pre-mature baby.

Answers: 7 .i. b. ii. a. iii. b. iv. b. v. b.

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Friday, November 5, 2021

CHAPTER-3: HUMAN REPRODUCTION MCQ class 12 Biology

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