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Karnataka 2nd PUC Biology Question Bank Chapter 3 Human Reproduction
2nd PUC Biology Human Reproduction NCERT Text Book Questions and Answers
Fill in the Blanks:
- Humans reproduce …………………….. (asexually/ sexually)
- Humans are …………………….. (oviparous, viviparous, ovoviviparous)
- Fertilization is …………………….. in humans, (external/internal)
- Male and female gametes are …………………….. (diploid/haploid)
- Zygote is …………………….. (diploid / haploid)
- The process of release of ovum from a mature follicle is called ……………………..
- Ovulation is induced by a hormone called ……………………..
- The fusion of male and female gametes is called ……………………..
- Fertilisation takes place in ……………………..
- The zygote divides to form …………………….. which is implanted in the uterus.
- The structure which provides a vascular connection between fetus and uterus is called ……………………..
- LH and FSH
- Fallopian tube
Draw a labelled diagram of male reproductive system.
Draw a labelled diagram of the female reproductive system.
Write two major functions each of testis and ovary.
Testes – Testes are the primary sexual organs in males. Two major functions of testes are
- Testosterone production from Leydig cells.
- Production of sperm cells in seminiferous tubules.
Ovary – Ovaries are the primary female sex organs. Two main functions of ovaries are
- Productions of female germ cells called eggs or oocytes.
- Production of hormones – estrogens & progesterone which affect many of the female secondary sexual characters & reproductive functions.
Describe the structure of a seminiferous tubule.
The testis has about 250 compartments (Testicular lobules) which contain 1-3 highly coiled seminiferous tubules. Each tubule is lined by 2 types of cells. Male germ cells (immature) (spermatogonia) and Sertoli cells.
Male germ cells form sperms by meiosis and Sertoli cells provide nutrition to these germ cells. Male germ cells and Sertoli cells together form germinal epithelium. A seminiferous tubule is covered outside by a basement membrane.
What is spermatogenesis? Describe the process of spermatogenesis.
Spermatogenesis is the production of sperms (n) by immature male germ cells (2n) at puberty inside the testis.
Hormonal role in spermatogenesis:
Spermatogenesis starts due to an increase in the secretion of GnRH (Gonadotropin-Releasing Hormone) by the hypothalamus. GnRH acts on the Anterior pituitary gland and stimulates the secretion of 2 gonadotropins – LH (Luteinizing Hormone) or ICSH (Interstitial Cell Stimulating Hormone) and FSH (Follicle Stimulating Hormone).
LH acts on Leydig cells for secreting testosterone and other androgens inturn stimulates process of spermatogenesis. FSH acts on sertoli cells which secretes some factors useful in spermiogenesis. Sertoli cells secrete inhebin that suppresses FSH synthesis.
It is the production of haploid spermatozoa from diploid spermatogonia inside the testis at puberty. At puberty, Spermatogonium undergoes mitosis forms 2 spermatogonia A and B. Both A and B are diploid with 46 chromosomes each.
A: Function as mother spermatogonia.
B: Grow in size to function as primary spermatocytes.
They then undergo meiosis to form 2 haploid cells called secondary spermatocytes (23 chromosomes). They then undergo 2nd meiotic division forming 4 haploid spermatids. These spermatids are transferred into spermatozoa (sperms) by spermiogenesis. After spermiogeneses, sperm heads become embedded into Sertoli cells and are released from seminiferous tubules by a process called spermiation.
Name hormones involved in the regulation of spermatogenesis.
After sexual maturity, spermatogenesis starts due to the secretion of gonadotropin-releasing hormone (GnRH) from the hypothalamus of brain. GnRH acts on pituitary gland and stimulates secretion of luteinizing hormone (LH) and follicle stimulating hormone (FSH). LH induce the Leydig’s cells of the testis to produce male sex hormones called androgens. High level of androgens stimulate the process of spermatogenesis. FSH acts on the Sertoli cells and stimulates secretion of some factors which help in the process of spermiogenesis.
Define spermiogenesis and spermiation.
Spermiogenesis is the final stage of spermatogenesis in which there is the maturation of spermatids into mature, motile spermatozoa. Spermiation is the release of mature spermatozoa from the surface of the Sertoli cell into the lumen of the seminiferous tubules
Draw a labelled diagram of sperm.
What are the major components of seminal plasma?
Seminal plasma consists of secretions of seminal vesicles, prostate gland and bulbourethral glands. It contains fructose, prostaglandins, citrate, inositol, dotting proteins, (secretions of seminal vesicles), calcium, phosphate, bicarbonate, enzymes, prostaglandins (secretions of prostate gland) and mucus (secretion of bulbourethral glands).
What are the major functions of male accessory ducts and glands?
Major functions of male-accessory ducts are
- Aid in sperm transport.
- Temporary storage of spermatozoa.
Male accessory glands secretions constitute the seminal plasma. These secretions are rich in fructose, ascorbic acid, citrate, calcium, certain enzymes and prostaglandins. These secretions nourish and activate the spermatozoa to swim.
What is oogenesis? Give a brief action of oogenesis.
Process of formation, development and maturation of haploid ovum or female gamete from diploid germinal cell of the ovary.
Cells of the germinal epithelium of ovary undergo repeated mitotic divisions to form diploid Oogonia or gamete mother cells. They are formed in the fetal ovary in large number by mitotic division from primary oocyte.
The primary oocyte enlarges and matures by taking food from the surrounding follicle cells. The mature primary oocyte undergoes its first meiotic division. It is an unequal division resulting in the formation of a large haploid secondary oocyte and a tiny first polar body or polocyte. The secondary oocyte remains bulk of the nutrient ride cytoplasm of the primary oocyte. The secondary oocyte undergoes second meiotic division which doesn’t proceed beyond metaphase until a sperm enters it. Ovulation occurs at this stage and the secondary oocyte is transferred to the fallopian tube.
Draw a labelled diagram of the section through the ovary.
Draw a labelled diagram of the Graafian follicle.
Draw diagramatic representation of various events during menstrual cycle.
Name the functions of the following.
- Corpus luteum
- Sperm tail
- Corpus luteum: It secretes the hormone progesterone, which prepares the uterus for implantation. If implantation fails the corpus luteum becomes inactive and degenerates. If an embryo gets implanted, the corpus luteum continues to secrete progesterone until the fourth month of pregnancy, after that the placenta takes over this function.
- Endometrium: It is the mucous membrane lining the uterus, which becomes progressively thicker and more glandular and has an increased blood supply in the latter part of the menstrual cycle. This prepares the endometrium for implantation of the embryo, but if this does not occur much of the endometrium breaks down and is lost in menstruation. If pregnancy is established the endometrium becomes the decidua, which is shed after birth.
- Acrosome: A membranous sac at or near the front of a sperm that assists in penetration of the egg. The acrosome contains enzymes, which are released when the sperm contacts the egg prior to fertilisation. The enzymes break down the outer layers of the egg to permit entry of
- Sperm tail: The tail is a fine vibrating posterior portion of the sperm which helps in swimming. This ability to swim (called motility) is essential for male fertility as the sperm has to swim up the vaginal canal, cervix and cervical canal to reach to the ovtim.
- Fimbriae: They help in the collection of ovum after ovulation.
Identify True / False statements. Correct each false statement to make it true,
- Androgens are produced by Sertoli cells.
- Spermatozoa get nutrition from Sertoli cells.
- Leydig cells are found in ovary
- Leydig cells synthesize androgens
- Oogenesis occurs in corpus luteum.
- Menstrual cycle ceases during pregnancy.
- Presence or absence of hymen is not a reliable indicator of virginity or sexual experience.
- False. Androgens are produced by Leydig cells.
- False. It is found in the testis.
- False. Oogenesis takes place in the ovary.
What is the menstrual cycle? Which hormone regulates the menstrual cycle?
The reproductive cycle in the female primates is called the menstrual cycle. The uterus linings become thick and spongy to receive fertilised egg. If the egg is not fertilized, this lining is not needed any longer so, it slowly breaks and comes out through vagina along with blood and mucous. This is called menstruation. It is repeated at an average interval of about 28/29 days.
Following hormones regulate this cycle:
- Luteinizing hormone
- Follicular stimulating hormone
What is parturition? Which hormones are involved in the induction of parturition?
The average duration of human pregnancy is about 9 months which is called 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 is called parturition. It is induced by hormone oxytocin which acts on the uterine muscle and causes stronger uterine contractions.
In our society women are blamed for giving birth to daughters. Can you explain why this is not correct?
Sex chromosome pattern in females is xx, i.e., both the gametes are with ‘X’ chromosomes. In males, sex chromosome is X Y i.e., one gamete with ‘X’ chromosome and other gametes with ‘Y’. So 50% sperms carry ‘X’ and 50% carry ‘Y’. A female child is producing when the sperm with ‘X’ chromosome fertilizes egg with ‘X’ chromosome. A male child is producing when sperm with ‘Y’ chromosome fertilizes egg with ‘X’ chromosome. Therefore sex of a baby depends on the father, not on the mother.
(a) How many egg are released by a human ovary in a month?
(b) How many eggs do you think would have been released if the mother gave birth to identical twins?
(c) Would your answer change if the twins born were fraternal?
(a) Only one egg is released by a human (female) ovary in a month.
(b) Only one egg is released if the mother gave birth to identical twins.
(c) Yes, two or more eggs are released in case fraternal twins are born.
How many eggs do you think were released by the ovary of a female dog, which gave birth to 6 puppies?
2nd PUC Biology Human Reproduction Additional Questions and Answers
2nd PUC Biology Human Reproduction One Mark Questions
Where are sperm produced in the testis?
In the seminiferous tubules of testis.
What is the role of placenta?
Provide nutrition to the developing embryo.
What is the function of amniotic fluid?
Protects foetus from shock.
Name the germ layer from which gonad develops.
Name the sperm lysin ? Which organelle secretes it ?
The process of formation of male and female gamete in the gonads is called gametogenesis.
The spermatogonia of an animal contains 32 chromosomes. What will be the number of chromosomes in its
(a) secondary spermatocyte
(b) spermatids respectively
(a) Secondary spermatocyte – 16 chromosome
(b) spermatids -16 chromosome
Name the structure formed from Graafian follicle after ovule?
Name the hormone secreted by corpusluteum.
Define spermiogenesis ? Where does it occur ?
The process of the transformation of spermatids into spermatozoa is called spermiogenesis. It occurs in the seminiferous tubules of testis.
Why middle piece of the sperm called power house of the sperm ?
Middle piece contains numerous mitochondria which produce energy for sperm movement.
The process of formation of mature female gametes.
Name the fluid filled space in the tertiary follicle.
What is the significance of secondary oocyte retaining the bulk of nutrient rich cytoplasm of the primary oocyte ?
These reserve food materials nourish the embryo till implantation.
When do the levels of FSH and LH reach the maximum in the menstrual cycle ?
The peak level of FSH and LH is reached in the middle of (14th day) menstrual cycle.
Implantation is the process in which the mammalian embryo (blastocyst) becomes attached to the endometriosis of the uterus.
What are the stem cells in human embryo?
Stem cells are those cells in the inner mass of the blastocyst, which have the potency to give rise to all tissues and organs.
What is colostrum ? How does it provide initial protection against diseases to new born infants. Give reason.
The milk produced during initial few days of lactation is called colostrum. It consists of several antibodies like IgA etc. which are essential for the development of resistance in new born babies.
2nd PUC Biology Human Reproduction Two Marks Questions
Name 2 types of cells present in the inner lining of seminiferous tubules. What are their functions?
Two types of cells in the inner lining of seminiferous tubule are
- Spermatogonia : Spermatogonia produces male gamete called spermatozoa.
- Sertoli cells : Sertoli cells provide nutrition to the developing spermatozoans.
Where are Leydig cells present? What is their role in reproduction?
- Ley dig cells are located in the interstitial space (space between the seminiferous tubule) in the testis.
- They secrete testicular hormones called androgens, mainly testosterone, this hormone regulates spermatogenesis.
Differentiate between vasa efferentia and vas deferens.
- Vasa efferentia are the ducts that leave the testis to open into epididymis. These are located inside the testis and are extra abdominal and do not receive the ducts of any glands.
- Vas deferens is the duct continues from epididymis. This ascends into the abdominal cavity. It receives the ducts of seminal vesicle.
Where are fimbriae present in a human female reproductive system ? Give their function.
Fimbriae are present in the free edges of the infundibulum of the fallopian tube. Then help in the easy capture of ova during ovulation.
Differentiate between endometrium and myometrium.
- Endometrium is the innermost glandular layer that lines the uterine cavity. It undergoes cylindrical changes during menstrual cycle. Implantation occurs in this layer.
- Myometrium is the middle thick layer of smooth muscles of the uterine wall. It doesn’t undergo any changes during menstrual cycle. It is responsible for the uterine movement.
Write the importance of inguinal canal in human reproductive system.
In males, the testis is formed in the abdomen close to kidneys. Soon after birth or at the 8th month of pregnancy, the testis descend into the scrotal sacs through a canal known as inguinal canal. If it is not present, the testis cannot reach to the scrotal sac.
Mention the sites of action of the hormones – GnRH and FSH, during spermatogenesis in human males. Give one function of each of the hormones.
GnRH acts on anterior pituitary and FSH acts on Sertoli cells of seminiferous tubules.
GnRH stimulates the release of two gonadotropin – Follicle-stimulating hormone and luteinizing hormone (LH) from the anterior pituitary. FSH stimulates the Sertoli cells to secrete some factors necessary for spermiogenesis.
Name the parts formed in the human embryo after
d. fifth month
b. Limbs and digits
c. Limbs and genital organs
d. Appearance of hair on head
Given below is the diagram of the sectional view of human ovum just after ovulation.
Mention the site of fertilization in the fallopian tube of a human female where the ovum and sperm meet.
Ampullary – Isthmus Junction.
How it blastula/blastocyte differ from Morula?
|(a) It is a hollow sphere of 32 or more cells formed by the rearrangement of blastomeres.
(b) Zona pellucida disintegrates with the enlargement of the blastocoel
|(a) It is a solid sphere of 8-16 cells blastomeres by cleavage of zygote.
(b) Zona pellucida is intact.
What are chroionic villi ? What is their fate?
The finger-like projections of the trophoblast produced after implantation are called chronic villi. Chroionic villi and uterine tissue become interdigitated with each other and jointly form the placenta.
While teaching “reproduction” in the class a student asked the teacher, “Why do human beings not reproduce by binary fission?” As a student of zoology, what will be your answer?
A human being is an advanced animal. He reproduces sexually. In man, the newborn is formed by the fusion of sperm (produced by father) and ovum (produced by mother). Binary fission is a type of asexual reproduction found only in primitive animals.
Write the functions of placenta in humans.
(a) It helps to supply oxygen and nutrients to the foetus.
(b) It helps in the removal of CO2 and other waste product formed by the foetus.
(c) Acts as endocrine gland by secreting hormone-like human placental lactogen, human chorionic gonadotropin, estrogen and progesteron which are necessary to maintain pregnancy.
2nd PUC Biology Human Reproduction Three/Five Marks Questions
Describe the accessary ducts of human male reproductive system.
The accessory ducts include rete testis, vasaefferentia, epididymis and vas deferens.
The seminiferous tubules end as short, straight tubules into rete testis. From the rete testis, 10-20 fine tubules called vasa efferentia leave the testis and open into the epididymis. The epididymis is a single convoluted tubule that is located along the posterior surface of the testis.
The epididymis leads into vas deferens that ascends into the abdomen and loops over the urinary bladder. It receives the ducts of seminal vesicle to form ejaculatory duct, that runs through the prostate and opens into the urethra, just after its origin from the urinary bladder. The urethra receives the ducts of prostrate and bulbourethral glands and runs through the penis to its external opening called urethral meatus.
Name the cells found
(a) inside the seminiferous tubules
(b) outside the seminiferous tubules in the human testis. Mention the function of each of them.
(a) Inside the seminiferous tubules are
- Spermatogonial cells
- Sertoli cells
(b) Outside the seminiferous tubules are Ley dig cells.
- Spermatogonial cells form spermatozoa.
- Sertoli cells provide nutrition to the germ cells and help in spermiogenesis.
- Ley dig, cells secrete the male sex hormone, testosterone.
During ovulation only one ovum is produced. But during one ejaculation about 200,000,000 sperms are released. Write the significance of increase in the number of sperms.
About 200 million (1 million = 10 lakhs) sperms are discharged by a single ejaculation. Since the sperms have to travel a great distance through the female genital tract there is trouble with chemical hazards and mechanical obstacles. Such a huge number of sperms is necessary to ensure a few to reach the anterior part of the fallopian tube, the site of fertilisation. Of the sperms only one sperm succeeds in fertilising the ovum present there.
Describe the structure of mammary glands of a human female with labelled diagram.
A mammary gland consists of glandular tissue and variable quantity of fat. The glandular tissue is divided into 15 – 20 mammary lobes and each lobe contains clusters of cells called alveoli, which opens into mammary tubules. The mammary tubules of each be join to form a mammary duct. Several mammary ducts join to form a wider mammary ampulla, which is connected to lactiferous duct through which milk comes out.
(a) Explain the role of ovarian hormones in inducing changes in the uterus during menstrual cycle.
(b) What triggers release of oxytocin at the time of parturition?
(a) Estrogen influences the uterus in the follicular phase. The endometrin is regenerated through protection. Progesterone influences the uterus in the luteal phase, the endometrin becomes further thickened and vascular for implantation
(b) Foetal ejection triggers the release of oxytocin.
Describe the events that take place during in fertilization in human being.
Fertilization refers to the fusion of a sperm and ovum in humans that occurs in the ampullary isthmic junction of the fallopian tube. When a sperm comes in contact with the zona pellucida of the ovum, it induces changes in the membrane that. blocks the entry of other sperms. The secretions of acrosome help the sperm to digest the zona pellucida and plasma membrane of the ovum and enter into its cytoplasm.
The entry of sperm induces the completion of secondary meiotic division of the secondary oocyte resulting in the formation of a second polar body and a large ootid. The haploid nucleus of the ootid and that of the sperm fuse to form a diploid zygote.
Describe the major steps in the development of a fertilized egg upto complete differentiation into blastocyst ready for implantation.
- The mitotic division called cleavage divisions start in the zygote as it moves through the isthmus of fallopian tube towards the uterus.
- The divisions result is 2,4,8,16 daughter cells, called blastomeres; the embryo with 8-16 blastomeres is a solid spherical structure and is called a morula.
- The morula continues to divide and the blastomeres rearrange themselves as it moves further into the uterus.
- As a result a hollow spherical structure, called blastocyst is formed.
- The blastocyst has an outer layer of cells, called trophoblast and an inner group of cells, called inner cell mass attached at one end of the trophoblast.
- The trophoblast layer becomes attached to the endometrium and the inner cell mass gets ready to form the embryo proper.
Draw a labelled diagram showing a human foetus developing within the uterus.
A connection between foetal membrane and uterine wall is known as placenta.
a. Mention the functions of placenta.
b. What is the fate of placenta after parturition?
c. Sometimes the expulsion of placenta is followed by bleeding. Give reason.
a. Functions of placenta
- It acts as a barrier between the foetus and the mother.
- It acts as an ultrafilter.
- Soluble inorganic and organic materials, nutrients, hormones, antibodies against diphtheria, small pox, scarlet fever, measles etc. can pass through the placenta from mother to foetus.
- It helps in the exchange of gases between the mother and the foetus.
- It helps in the elimination of nitrogenous discharges and other wastes of the foetus.
It acts as an endocrine gland and produces hormones such as HCG, chorionic thyrotropin, chorionic corticotropin, chorionic somatomammotropin, estrogens and progesterone. It also secretes progesterone until the end of pregnancy. At the time of parturition, the placenta secretes relaxin, which helps in the relaxation of pubic ligaments to enable birth of the child.
b. Shortly after the baby is born, the placenta and the remains of the umbilical cord, known as the afterbirth is expelled out.
c. Because the vascular tissues are damaged in the process of parturition.