Human Reproduction Class 12:- Humans are the sexually reproducing viviparous organisms.Reproduction is a biological process by which organism produce their young one to continue their race on the earth.The male and the female both have their different reproductive organs. The males reproductive system consists of pair of testes,the male sex accessory ducts and the accessory glands and the external genitalia.The female reproductive system consists of a pair of Ovaries,a pair of oviduct,a uterus,a vagina, external genitilia,and a pair of some steroid hormone.
Human Reproduction Class 12 – Very Short Answer Type Questions
Q.1. Make a list of the following events which are observed in human reproduction in the chronological order. Fertilization,gestation,parturition, implantation,insemination,gametogenesis.
A.1. Following are the sequence of events which are occurring in the process of human reproduction:
- Gametogenesis
- Insemination
- Fertilization
- Implantation
- Gestation
- Parturition
Q.2. Write the significance of the cervix in female reproductive system.
A.2. Cervix is the narrow opening through which the uterus opens till up to the vagina. Cervical canal is the cavity of cervix that alongside the vagina goes on to form birth canal.
Q.3. Write the reason for the absence of menstrual cycles during the conception or pregnancy?
A.3. During the pregnancy, all events of the menstrual cycle gets stop and there is no menstruation. The menstruation occurs only when the egg which is released is not fertilized. But in the pregnancy, the released egg is fertilized and therefore the uterus lining does not shed out, instead of this it nourishes the fetus. That’s why a woman may experience uterine bleeding during the pregnancy due to various reasons. It is not the reason of the period.
Q.4. Fill the missing data in the table where in the Column A shows female reproductive organs and in the Column B shows its respective functions.
| Column A(Organs) | Column B(Corresponding Functions) |
| Pregnancy | |
| Vagina | Birth |
| Ovaries | Ovulation |
| Oviduct |
Human Reproduction Class 12
A.4. Following are the female reproductive organs and their associated functions.
| Column A(Organs) | Column B(Corresponding Functions) |
| Uterus | Pregnancy |
| Vagina | Birth |
| Ovaries | Ovulation |
| Oviduct | Fertilization |
Q.5. Write the name of the hormone crucial in parturition. Does the signal of parturition originate from the mother or the fetus?
A.6. The hormone that is crucial for parturition is Oxytocin. Signal originates from placenta and fully developed fetus that initiate the foetal ejection reflex which triggering the release of the hormone, oxytocin.
Q.7. Write the role of epididymis in male fertility.
A.7. This is situated along with the posterior surface of each testis where the spermatozoa acquire motility and capacity to fertilize the egg. The surface of sperm is altered in the response to secretions of epididymis, that is a key to achieve the ability to fertilize an egg.
Q.8. Write the names of the hormones, endocrine glands along with the functions of hormones which are crucial in causing spermatogenesis.
A.8. The given table below provides the required data:
| Name of the hormone | Endocrine glands where the hormone is released | Functions of the hormone |
| Gonadotropin-releasing hormone(GnRH) | Hypothalamus | The increase in secretion of GnRH that initiates spermatogenesis at the age of puberty age, After acting on the anterior pituitary gland – triggers the secretion of LH and FSH |
| Luteinising hormone(LH) | Anterior pituitary gland | Triggers the production and secretion of androgens |
Q.9. Write the events which cause the chromosome number of gametes to go from 2n, n, and again back to the 2n during reproduction.
A.10. The Chromosomes replicate once but they divide twice. The chromosomes undergo mitosis, first meiotic cell division and the second meiotic cell division, outcome of which is n number of the chromosomes. And it fuse with the haploid(n) sex gamete of opposite sex to form a diploid(2n) cell during the process of reproduction.
Human Reproduction Class 12 Quiz
Q.11. What is difference between the primary oocyte and the secondary oocyte?
A.11. Primary oocyte is a diploid type of cell whereas the secondary oocyte is a haploid type of cell. Primary oocyte is formed when the oogonia are at the prophase-I of the meiotic division in avfoetal ovary whereas the secondary oocyte is formed from the primary oocyte after the meiosis – I division to produce the ova in females during the stage of puberty.
Q.12. Write the role of ampullary-isthmic junction in the female reproductive system.
A.12. In the ampullary-isthmic junction, the process of fertilization of the ovum takes place.
Q.13. How zona pellucida of the ovum checks the polyspermy ?
A.13. Zona pellucida is a thick layer which is girdled by corona radiata cells. During the fertilization, cortical granules are released from the egg that blocks the fusing of multiple sperms with an egg.
Human Reproduction Class 12
Q.14. Write the significance of LH surge through the menstrual cycle .
A.14. LH Surge triggers rupture of the Graafian follicle and causes the release of the ovum in the fallopian tube in female reproductive system.
Q.15. In which stage of cell division are the spermatids formed from the secondary spermatocytes?
A.15. In the second meiotic division.
Human Reproduction Class 12 – Short Answer Type Questions
Q.1. Write the significance of the following stages during the lifetime of a female.
- Menarche
- Menopause
A.1. The first menstruation or the onset of the menstruation at puberty is called as menarche.That indicates the attainment of the sexual maturity and the commencement of the fertile period or the normal period the female. Menstruation cycle is cycle of the events from the one up to till the next menstruation and this is repeated for about the 28 days on an average wherein one ovum is released.The Menopause, on the other hand, is when the menstruation cycle comes to a halt or to stop, it indicating the end of the fertile period of the female as the process of ovulation stops. The Cyclic menstruation denotes the regular reproductive phase stretching from the menarche to menopause.
Q.2.
a. How many number of spermatozoa does one secondary spermatocyte produce?
b.In which part of the zygote does the first cleavage division occur?
A.2. a. Secondary spermatocytes undergo the meiotic division – II to generate the four haploid spermatids through which the process of the spermiogenesis are transformed into spermatozoa.
A.2. b. The Cleavage occurs within the fallopian tube and it is holoblastic, dividing the zygote completely into the blastomeres. First cleavage divides the zygote longitudinally into the two blastomeres wherein one is slightly larger than the other.
Q.3. Why the corpus luteum stay active throughout pregnancy and in the absence of fertilization, is active only for 10-12 days in the female?
A.3. During at the luteal phase, the leftover or the remaining parts of the Graafian follicle transform into the corpus luteum. It discharges the large quantities of the progesterone hormone which is required for the maintenance of the endometrium wall. The endometrium is important for the implantation of the fertilized egg and for the various other stages of pregnancy. Therefore, the corpus luteum has a long life in pregnancy. In the absence of the fertilisation, upholding of the corpus luteum is not required and therefore it declines within 10-12 days, that causes the lining of the endometrium wall to menstruate and therefore the onset of the new menstrual cycle.
Q.4. Define the foetal ejection reflex. How does foetal ejection reflex causes parturition?
A.4. The Foetal ejection reflex is the mild uterine contractions which arise or generated from the parturition signals from the fully developed fetus and the placenta. This reflex stimulates the release of the oxytocin, that causes the uterine contractions, in turn of, stimulating the increased secretion of oxytocin. This action of the uterine contractions and the oxytocin secretion further results in the stronger contractions leading to the dilation and therefore expulsion of the baby out of the uterus through the cervical canal, expelling placenta along, therefore the parturition or childbirth occurs.
Human Reproduction Class 12
Q.5. Write the functions of the placenta other than its endocrine function.
A.5. The placenta promotes to the supply of nutrients and the oxygen to the embryo. This also facilitates the elimination of excretory wastes and the carbon dioxide produced by the embryo. The Placenta aids in the transportation of the substances to and from the embryo as this is connected to the embryo through the umbilical cord.
Q.6. Why is the breastfeeding recommended during the initial stages of infant growth?Give the reason.
A.6. The mammary glands or the milk gland in females start producing milk towards the end of the pregnancy through the process of lactation which helps the mother to feed the newborn. The Colostrum is the first milk produced during the initial few days. The Colostrum contains the antibodies which are crucial in developing the resistance in the newborns, therefore it is recommended by the doctors to bring up a healthy baby.
Human Reproduction Class 12
Q.7. Write the different stages of the follicular phase of the menstrual cycle taking place in the ovary and the uterus.
A.7. In this phase,the primary follicles transform into the fully mature Graafian follicle inside the ovary. The endometrium wall of the uterus simultaneously regenerates through the proliferation. The changes in the levels of ovarian and the pituitary hormones induce changes in the uterus and the ovaries. During this stage, the secretion of the FSH and the LH eventually increases and triggers the secretion and the follicular development of the estrogen by the growing follicles. In the middle of the this cycle, both the LH and the FSH reach the peak level. This speedy secretion of the LH at the maximum level during the mid-cycle causes rupture of the Graafian follicle and therefore the ovulation.
Human Reproduction Class 12 study materials
Q.8. Describe the changes that taking place during the transition of a primary follicle to the Graafian follicle in the oogonia.
A.8.The Oogonia or the gamete mother cells are formed within the each fetal ovary. Their is no more oogonia are formed after birth. They enter into the prophase-I stage of the meiotic division when they start cell the division to approach the primary oocyte stage. These primary oocytes are girdled by the layer of the granulosa cells to form the primary follicle which degenerates during the stages of the birth to the puberty. The primary follicles are encircled by more layers of the granulosa cells and a new theca called as secondary follicles. This theca is subdivided into the other theca externa and an inner theca interna which secretes the estrogen. The secondary follicle is then transformed into the tertiary follicle characterized by the antrum, that is a fluid-filled cavity. At this phase, of the primary oocyte grows in size inside tertiary follicle to complete the first meiotic division. The tertiary follicle finally takes transitions to form the Graafian follicle.
Q.9. What is Parturition?
A.9. The Parturition refers to the process of delivering a baby from the uterus to the vagina to the outside world from the mother’s body. There are three types of stages of Parturition:
- Dilation.
- Expulsion.
- Placental.
Q.10.What is Fertilization?
A.10. The Fertilization refers to the biological process of the fusion of male and the female gametes resulting in the formation of a zygote. In humans beings,the fertilization process takes place in the fallopian tube of the reproductive system.
Q.11. What are the main functions of each testis and the ovary?
A.11.. Tests are also known as the Testicles. It is a pair of the oval-shaped organs that is masked in a pouch known as the scrotum. It is responsible for the production of the sperms and the male hormone that is testosterone.
The ovary is a ductless reproductive gland, which helps in functioning by producing a female sex hormone known as estrogen and it is also involved in producing and the storing the ovum or the egg cell.
Human Reproduction Class 12 – Long Answer Type Questions
Q.1. Describe the role of the pituitary gonadotropins during the follicular and theovulatory phases of the menstrual cycle. Explain the shifts in steroidal secretions.
A.1. The menstrual flow or the bleeding is due to the breakdown of the lining of the uterine endometrium wall and blood vessels that forms the liquid discharged from the vagina. The menstrual cycle is controlled by the pituitary gland through the hypothalamus. The Changes in the ovary and the uterus during the menstrual cycle is due to the fluctuation in the levels of the ovarian and the pituitary hormones. Towards the end of the menstrual phase, the pituitary FSH eventually increases that causes the development of follicles inside the ovaries. Both the FSH and the LH attain or achieve a peak level during the mid of the cycle. This speedy secretion of the LH leads to the LH surge that induces the rupture of the Graafian follicle and therefore the ovulation. During the maturation of the follicles, more of the estrogen is secreted causing a surge in the FSH and the LH from the anterior pituitary. The LH surge causes the ovulation. The LH also induces or persuade luteinisation. The LH hormone causes conversion of the empty follicle in the form of the corpus luteum. The Corpus luteum produces the steroidal hormones – progesterone and the estrogen. These hormones rule the growth and the maintenance of the uterine endometrium for the probable implantation.
Q.2. Write in detail the difference between the meiotic division of oogenesis and the spermatogenesis.
A.2. The Spermatogenesis is the process of production sperm from the male germ cell whereas the oogenesis is the process of production the eggs from the oogonia in females. The meiosis is different in the spermatogenesis and the oogenesis in the quantity of the end product. This is the unequal division that is necessary to maintain the essential constituent of the cytoplasm. The one minor part is detached as the polar body where as a single daughter cell known as the ovum is formed which is functional. But in the spermatogenesis, the four spermatids are produced which are the functional and that later develops into the spermatozoa.
| Oogenesis | Spermatogenesis |
| The production of eggs from the oogonia in the female. | The production of the sperm from the spermatogonia |
| It takes place inside ovary of the females | It takes place inside the testes in the males |
| All except last phase takes place inside the ovary of the female | The all phases occur inside the testis |
| The early stages are observed during the fetal period. The rest stages observed between the puberty and the menopause | It is a continuous process which is initiated from the puberty and lasts until the death |
| The matured from germinal the epithelium overlying the ovary | It is developed from the germinal epithelial lining of the seminiferous tubules |
| The Sertoli cells is not found in the germinal cell epithelium | The sertoli cells found in the germinal cell epithelium |
| Few of the oogonia divide to produce the eggs, one at a time | Th spermatogonia are divided by the meiosis to produce sperms |
| This is the lengthy growth phase in oogonia | The growth phase of the spermatogonia is short |
| It generates the non-motile gametes | It produces the motile gametes |
| The primary oocyte divides to form the secondary oocyte and the polar body during meiosis-I | During the meiosis-I, primary spermatocyte divides to form the two secondary spermatocytes |
Q.3. Define Reproduction.Describe how the humans reproduce their young ones?
A.6. Reproduction is a biological process of producing young ones or offspring, that are identical to their parents to continue their race on earth. The process of reproduction is of two different modes of and are classified mainly based on the involvement of the parents.
Following are the two different modes of reproduction are:
Asexual Reproduction: In this mode of reproduction they involves only one parent and the new offspring produced that is genetically similar to the parent.
Sexual Reproduction: In this mode of reproduction involves the formation and the transfer of gametes, followed by the fertilization, the formation of the zygote and embryogenesis. It is very complex process.
Humans beings and all mammals reproduce their young ones through the sexual mode of reproduction.
Q.4. How many number of eggs does a woman have?
A.4. As the fetus early in development, the female produces about 6 million to 7 million eggs.
And At birth, they are approximately 1 million eggs. By time of puberty, only about 300,000 eggs remaining. Out of these eggs only 200 to 300 eggs will be ovulated during the woman’s reproductive lifetime. The fertility can drop as a woman ages due to the decreasing number and quality of the remaining eggs.
Q.5. Write about the female reproductive system.
A.5.Female reproductive system involves both the internal and the external organs. These organs are mainly included with the reproduction process.
- Internal Reproductive Organs
The females internal reproductive organs include the vagina, uterus (womb), cervix, fallopian tubes and ovaries.
- External Reproductive Organs
The females reproductive organs involve vulva consists of all of the external parts of female reproductive organs.
Q.6.Define Menopause.
A.6. The Menopause is final stage or end of the woman’s menstrual cycle, the fertility and the different types of changes a woman experiences. It is a natural process in all thecfemales and happens in all older women, between age of 40 and 50, therefore it may also vary. The main reason for the menopause is the female sex hormone levels, that naturally reduces along with the age and eventually the ovaries stop releasing the eggs. Hence,women in this phase no longer have their periods and they are not able to get pregnant.
Q.7.Define menstrual cycle.Write the name of the Hormones that control the menstrual cycle.
A.7.It is defined as the natural process, that occurs in all females after reaching the age of their puberty. At this period, an ovary releases a mature egg, that travels to the uterus, if the egg is not fertilized, uterine lining sheds and a new cycle begins. The menstrual cycle lasts for 28 days. The Menstrual cycles may either last for 21 days or as long as for 35 days in some individuals.
This entire process of the menstrual cycle is controlled by endocrine system and hormones involved are FSH, LH, estrogen, and progesterone. Both the FSH and LH hormones are produced by gonadotropic cells and the progesterone hormones are produced by ovaries.
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