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Karnataka 2nd PUC Biology Question Bank Chapter 3 Human Reproduction
2nd PUC Biology Human Reproduction One Mark Questions and Answers
Question 1.
What is gametogenesis?
Answer:
The process of production of haploid gametes from diploid gonial cells of the gonads is called gametogenesis.
Question 2.
Define Placenta?
Answer:
The placenta is an association of foetal and maternal tissues for the purpose of attachment and physiological exchange.
Question 3.
What is nebenkern?
Answer:
The mitochondrial sheath present in the middle piece of sperms is called nebenkern.
Question 4.
Which hormone is called pregnancy hormone?
Answer:
Progesterone.
Question 5.
Define Amphimixis.
Answer:
Amphimixis is the fusion of the pronucleus of the sperm with that of the egg.
Question 6.
Define implantation.
Answer:
Implantation is the process in which the mammalian embryo (blastocyst) becomes attached to the endometrium of the uterus.
Question 7.
Define spermiogenesis.
Answer:
It is the process in which non motile spermatid develops into motile sperm or spermatozoan.
Question 8.
Name the membrane around fertilized egg which prevent polyspermy.
Answer:
Fertilisation membrane.
Question 9.
Name the endocrine part of the testes.
Answer:
Intestitial cells or leydig’s cells.
Question 10.
What do you mean by manchette?
Answer:
It is the cytoplasmic content of the middle piece in sperm.
Question 11.
What is fertilisin?
Answer:
Fertilisin is a gynogamone produced by ovum during approximation of gametes.
Question 12.
What is antifertilisin?
Answer:
It is the androgamone produced by sperm during approximation of gametes.
Question 13.
What is acrosome reaction?
Answer:
Acrosome of the sperm releases lytic enzymes to help in dissolving the membranes surrounding the egg and to facilitate entry of the sperm into the egg.
Question 14.
Define blastulation?
Answer:
Formation of blastula with a hollow cavity (blastocoel) from morula is called blastulation.
Question 15.
What is antrum?
Answer:
The cavity found within the graafian follicle containing fluid rich in FSH and LH is called antrum.
Question 16.
What is liquor folliculi?
Answer:
It is the fluid present in antrum cavity secreted by grantilosa a cells of graafian follicle. It is rich in FSH and LH.
Question 17.
Define fertilisation?
Answer:
The process of union of male and female gametes is known as fertilisation.
Question 18.
Name the gametokinetic factor?
Answer:
FSH.
Question 19.
Where are sperms produced in the testis?
Answer:
In the seminiferous tubules of testis.
Question 20.
What is the role of placenta?
Answer:
To provide nutrition to the developing embryo.
Question 21.
Define gametogenesis.
Answer:
Production of gametes by gonads is called gametogenesis.
It is of two types.
- Spermatogenesis and
- Oogenesis.
Question 22.
Name the hormone secreted by corpus luteum.
Answer:
Progesterone.
Question 23.
Define spermiogenesis? Where does it occur?
Answer:
The process of the transformation of spermatids into spermatozoa is called spermiogenesis. It occurs in seminiferous tubules of testis.
Question 24.
Expand (one mark each)
(a) IVE
(b) ZIFT
(c) IUT
(d) GIFT
(e) ICSI
(f) AI
(g) IUI
(h) ART
Answer:
IYE-in vitro fertilization
ZIFT – zygote intra fallopian transfer
IUT – intra uterine transfer
GIFT – gamete intra fallopian transfer
ICSI – intra cytoplasmic sperm injection
AI – artificial insemination
IUI – intra uterine insemination
ART – assisted reproduction technologies.
Question 25.
Name the functions of the following: (one mark each)
(a) Corpus luteum
(b) Endometrium
(c) Acrosome
(d) Sperm tail
(e) Fimbriae.
Answer:
(a) Corpus luteum : It secretes hormones like progesterone and estrogen.
(b) Endometrium : Undergoes cyclical changes during menstrual cycle and also act as a site for the implantation of the fertilized ovum.
(c) Acrosome : Filled with hydrolytic enzymes that help in fertilization of the ovum by sperm, (hyaluronidase).
(d) Sperm tail: Facilitate sperm motality essential for fertilization.
(e) Fimbriae: Help in collection of the ovum after ovulation.
Question 26.
Name the layer of cells that forms the outer wall of blastocyst.
Answer:
Trophoblast.
Question 27.
What is menarche?
Answer:
The first menstruation which starts in females at puberty is called menarche.
Question 28.
Name the finger like projections that appear on the trophoblast after the implantation.
Answer:
Chorionic villi.
Question 29.
What is the significance of scrotum?
Answer:
It helps to maintain the lower temperature of the testes by 2-2.5°C less than body temperature which is necessary for spermatogenesis.
Question 30.
What is foetal-ejection reflex?
Answer:
Mild uterine contractions that trigger release of oxytocin from the maternal pituitary is known as foetal-ejection reflex.
Question 31.
“Colostrum is considered as essential for newborn baby”. Give reason.
Answer:
Colostrum contains several antibodies which provide immunity to the new born baby.
2nd PUC Biology Human Reproduction Two Marks Questions and Answers
Question 1.
Explain fertilizin and antifertilizin reactions.
Answer:
These are the sex hormones which are responsible for the approximation of gametes. The sperm produces antifertilizin and egg produces fertilizin. The fertilizin of egg attracts sperms by interacting with antifertilizin and it is species specific.
Question 2.
Give two differences between spermatogenesis and oogenesis.
Answer:
Spermatogenesis | Oogenesis |
1. It occurs in seminiferous tubules of testes. | It occurs in the follicles of ovary |
2. Four functional sperms are produced from each spermatocyte. | One functional ovum is produced from each primary oocyte; the polar bodies are non functional |
Question 3.
Mention the significance of fertilization.
Answer:
Significance of fertilization:
- Brings the fusion of gametic haploid nuclei and restores the diploid number of chromosoma number of the species.
- Activates the egg to undergo development. (ATP synthesis)
- Allows the recombination of parental genes to effect variations.
- Brings about the polarity of the future embryo.
- Increases metabolic activity and rate of protein synthesis in the egg.
Question 4.
Name two gonadotrophic hormones with a function of each.
Answer:
a. FSH (Follicle Stimulating Hormone): It stimulates the development of follicles of ovary in females and spermatogenesis in males.
b. LH (Luteinizing hormone): It stimulates the ovulation and the formation and maintenance of corpus luteum.
Question 5.
What is fertilization membrane? How it is formed?
Answer:
The membrane formed by the contents of cortical granules of egg in the perivitelline space is called fertilization membrane. It prevents the polyspermy condition in human beings.
The cortex has a number of granules that rupture and release their contents. The contents released at the vitelline membrane become applied to the inner surface of the vitelline membrane which is very thick. This thickened membrane is called fertilization membrane.
Question 6.
What is corpus luteum? What is its function?
Answer:
Empty or ovulated graafian follicle is known as corpus luteum.
Function: It secretes progesterone which maintains pregnancy.
Question 7.
Mention any two functions of testosterone.
Answer:
a. It stimulates the growth of various parts of the reproductive system in males.
b. It influences the spermatogenesis and development of secondary sexual characteristics such as deepening of voice, greater skeletal and muscular growth.
Question 8.
Distinguish between oogonium and ovum.
Answer:
Oogonium | Ovum |
1. It is a diplod cell. | It is the haploid cell. |
2. It is not a gamete but a sex organ. | It is a gamete. |
3. It undergoes series of divisions both mitotically and meiotically to produce ovum. | It cannot produce oogonium. |
Question 9.
What is acrosome? Mention its role in fertilization.
Answer:
The anterior end of the sperm nucleus partially covered by a cap like structure formed from the golgi complex of spermatid is called acrosome. It contains several hydrolytic enzymes. At the time of fertilization, the acrosome releases lytic enzymes to help in dissolving the egg membranes and penetrate through them.
Question 10.
Give any four differences between external and internal fertilization.
Answer:
External fertilization | Internal fertilization |
1. It occurs outside the body generally in an aquatic medium. | It occurs in side the female body. |
2. Physical contact between male and female is not necessary. | Mating is essential. |
3. No special organs of copulation are present. | Special organs of copulation are present. |
4. Generally numerous eggs are laid. | Number of eggs laid are limited. |
Question 11.
Explain the role of gonadotrophic hormones in the female reproductive cycle.
Answer:
(a) FSH (Follicle stimulating hormone): It stimulates the development of follicles of ovary in females.
(b) LH (Luteinizing hormone): It stimulates the ovulation and the formation and maintenance of corpus luteum.
Question 12.
Briefly explain implantation.
Answer:
About 24 hours after fertilization zygote begins rapid and orderly pattern of divisions. As a result of cleavage an embryo having a spherical mass of 32 cells is formed. This stage is called morula. It reaches the uterus due to peristalsis and ciliary action of fallopian tube. Morula which is bathed in nutritive fluid secreted by the uterine glands, gets converted into blastula of 58 cell stage. Within the next five days it attaches to the wall of the uterus.
This process is called implantation. During this process, the cells of the trophoblast secrete proteolytic enzymes which dissolve a small area in the uterine wall. This creates a depression to accommodate the blastocyst.
Question 13.
With reference to the study of human sperm, mention the functions of acrosome, proximal centriole, distal centriole and nebenkern.
Answer:
Acrosome : It releases hydrolytic enzymes to dissolve (penetrate) egg membranes and help the sperm to penetrate through them.
Proximal centriole: It produces spindle apparatus during Amphimixis.
Distal centriole: It produces axial filament which forms the axis of middle piece and tail.
Nebenkern: It is the mitochondrial sheath which provides the energy for the movement of the sperm.
Question 14.
Write two major functions each of testis and ovary.
Answer:
(a) Testes: Production of spermatozoa (spermatogenesis) and secretion of male sex hormone (testosterone).
(b) Ovary: Formation of ovum (oogenesis) and secretion of female sex hormones (oestrogen and progesterone).
Question 15.
Describe the structure of a seminiferous tubule.
Answer:
Seminiferous tubules are highly coiled tubular structures present in testicular lobules of testis. The wall of each seminiferous tubule is lined by germinal epithelium. Majority of cells of this epithelium are cuboidal called male germ cells (spermatogonia), but a few large cells called Sertoli cells or sustentacular cells. The male germ cells grow into primary spermatocytes, which undergo meiosis to produce spermatozoa.
Question 16.
Name the hormones involved in the regulation of spermatogenesis.
Answer:
GnRH, LH, FSH and Testosterone.
Question 17.
Define spermiogenesis and spermiation.
Answer:
(a) Spermiogenesis: Transformation of non motile spherical spermatids into motile spindle shaped spermatozoa is called spermiogenesis.
(b) Spermiation: The process of release of sperms from seminiferous tubules is called spermiation.
Question 18.
What are the major components of seminal plasma?
Answer:
The secretions of the male accessory glands (seminal vesicles, prostate gland and bulbourethral glands) is called seminal plasma. It is rich in fructose, calcium and certain enzymes.
Question 19.
What are the major functions of male accessory ducts and glands?
Answer:
Male accessory ducts store and transport the sperms from the testes to the outside through urethra. The male accessory glands produce seminal plasma, which is rich in fructose, calcium and certain enzymes. The mucoid secretions of bulbourethral glands helps in the lubrication and smooth flow of seminal plasma in the urethra and its descent in the vagina.
Question 20.
What is menstrual cycle? Which hormones regulate menstrual cycle?
Answer:
The cycle of events starting from one menstruation till the next one in human females, is called menstrual cycle. It is a reproductive cycle in which one ovum is produced and released. Gonadotropins (LH and FSH) released by pituitary gland, and ovarian hormones (progesterone) regulate menstrual cycle.
Question 21.
What is parturition? Which hormones are involved in induction of parturition?
Answer:
The process of delivery of the foetus (child birth) is called parturition. The hormones oxytocin and relaxin are involved in the induction of parturition.
Question 22.
What is colustrum? What is its significance to the new born baby?
Answer:
The milk secreted from mammary glands just after birth for 2 or 3 days is called colustrum. It is rich in proteins and low in fats. It also contains antibody IgA which provides immunity to the new born infant.
Question 23.
What is parturition? Name the neuroendocrine hormone that induces parturition.
Answer:
The process of delivery of foetus (child birth) is called parturition. Oxytocin.
2nd PUC Biology Human Reproduction Three Marks Questions and Answers
Question 1.
Draw a labelled diagram of a section through ovary.
Answer:
2nd PUC Biology Human Reproduction Five Marks Questions and Answers
Question 1.
Describe oogenesis.
Answer:
Oogenesis: The formation of ova or eggs from the diplod oogonial cells of the ovary is called oogenesis. Primordial germ cells give rise to oogonial cells and follicular cells (nurse cells). It is the oogonial cells that develop into ova. Oogenesis involves three phases, viz.,
1.. Multiplication phase
2. Growth phase
3. Maturation phase
1. Multiplication phase: The diploid oogonial cells of the ovarian follicles divide repeatedly by mitosis to produce more oogonial cells. Among them only a few will enter into growth phase and others are kept in reserve.
2. Growth phase: During this phase, few oogonial cells synthesise yolk or vitelline in the cytoplasm and transform into primary oocytes. Hence this phase is also called vitellogenesis. During the growth of oogonial cells into primary oocytes, follicular cells or nurse cells or granulosa cells assist vitellogenesis.
3. Maturation phase: This phase involves two successive divisions namely meiosis I and meiosis II. The meiosis I is a reductional cell division resulting in the formation of a smaller cell often called the first polar body and larger secondary oocyte. The larger secondary oocyte undergoes meiosis II to form a larger cell called ootid or ovum and a smaller cell called as second polar body. The first polar body may also undergo meiosis II to produce two more secondary polar bodies. So at the end of oogenesis one ovum and three polar bodies are formed. These polar bodies will not survive. They undergo disintegration.
Question 2.
Describe the process of spermatogenesis up to the formation of spermatids. Mention the fate of spermatids.,
Answer:
Spermatogenesis:
Formation of haploid sperms from the diploid spermatogonial cells of the testes is called spermatogenesis. Primordial germ cells give rise to spermatogonial cells and sertoli cells. It is the spermatogonial cells that develop into the spermatozoa. Spermatogenesis involves four phases., viz..
a. Multiplication Phase
b. Growth Phase
c. Maturation Phase
d. Spermiogenesis
(a) Multiplication Phase: The diploid spermatogonial cells of the seminiferous tubules divide repeatedly by mitosis to form more spermatogonial cells. Among them only a few will enter into growth JS phase and others are kept in reserve.
(b) Growth Phase: Spermatogonial cells obtained from multiplication phase grow in size, however they still remain diploid. These cells are now called primary spermatocytes.
(c) Maturation Phase: This phase involves two successive divisions, viz., Meiosis I and Meiosis II. The meiosis I is reductional and two haploid cells are formed from each primary spermatocyte. The resultant cells of I meiotic division are called secondary spermatocytes. These secondary spermatocytes undergo meiosis II which is equational. As a result each secondary spermatocyte produces two haploid cells of equal size called spermatids. Hence, four haploid M spermatids are formed during maturation phase g from each diploid primary spermatocyte.
(d) Spermiogenesis: Spermatids are not gametes, they are ordinary haploid cells. During spermiogenesis or spermateliosis each spermatid in association with sertoli cells become tadpole like, flagellated and highly motile gamete called spermatozoan or sperm.
Question 3.
Describe the role of hormones in the female reproductive cycle.
Answer:
Role of hormones in the female reproductive cycle :
i. Gonadotropins of the pituitary: The FSH and LH play a vital role in the development of ovarian follicle. LH also stimulates the ovulation and the formation and maintenance of the corpus luteum.
ii. Ovarian hormones:
(a) Estrogen: It stimulates the growth of various parts of the reproductive system including uterus, It stimulates the development of female secondary characteristics such as high pitched voice, deposition of the fat in particular area to produce female body contour. It also stimulates the development of mammary glands.
(b) Progesteron: It promotes the development of uterine mucosa and prepares it for implantation and increases its secretory activity. It stimulates mammary gland development. It maintains, pregnancy and prevents premature expulsion of the foetus. It inhibits ovulation.
iii. Hormones of the placenta: It secretes estrogen, progesterone and the human chorionic gonadotropin. All these support to maintain pregnancy by,
(a) Extending the life of the corpus luteum.
(b) Keeping the FSH and LH levels low.
Question 4.
Describe briefly the structure of a human sperm.
Answer:
Sperm is a male gamete produced in the testes by spermatogenesis. The shape and the size of the sperm varies from species to species. However all the animal sperms show a common structure.
Typical structure of sperm shows four regions. They are
(a) Head
(b) Neck
(c) Middle piece
(d) Tail
(a) Head: Head is the anterior segment of the sperm which is oval in shape. Head includes a haploid sperm nucleus and a little cytoplasm. The sperm is devoid of yolk. The head is covered by a cap like structure called acrosome, containing hydrolytic enzymes. Acrosome helps the sperm to penetrate ovum. Acrosome is formed by golgi apparatus.
(b) Neck: It is an indistinct part that connects the head and the middle piece, it includes a proximal centriole close to the sperm nucleus.
(c) Middle piece: It contains a distal centriole and an axial filament. Surrounding the axial filament mitochondrial sheath is present which provides energy needed for the movement of the sperm. Hence middle piece may also be referred to as engine room of the sperm. Axial filament is also called axoneme and arises from the distal centriole which forms the axis of the tail.
(d) Tail: It is divided into two parts namely,
1. Main piece: It is covered by a cytoplasmic sheath.
2. End piece: It is naked and forms the terminal part of the tail.
The tail shows lateral undulating motion and bring about the propulsion of the sperm.
Question 5.
Draw a labelled diagram of male reproductive system.
Answer:
Question 6.
Draw a labelled diagram of female reproductive system.
Answer:
Question 7.
Explain the menstrual cycle with a diagram.
Answer:
Question 8.
Differentiate between spermatogenesis and oogenesis.
Answer:
Spermatogenesis | Oogenesis |
1. It occurs inside the tests | 1. It occurs inside the Ovary |
2. All the stages are completed inside the tests. | 2. Majority occurs inside the ovary but last stages occur in the oviduct. |
3. Spermatogonia develop from the germinal epithelium lining in the seminiferous tubules. | 3. Oogonia develop from the germinal epithelium overlaying the ovary. |
4. All spermtogonia give rise to spermatocytes | 4. Only few oogonia give rise to oocytes. |
5. Primary spermatocytes divide by meiosis I to give rise to two secondary spematocytes | 5. Primary spermatocytes undergoes meiosis I to give rise to one secondary oocyte and a polar body |
6. Secondary spermtocyte divides by meiosis II to give rise to two spermatids | 6. Secondary oocyte divides by meiosis II to form the ovum and the second polar body. |
7. Each spermatid differentiates into spermatozoan or sperm. | 7. No differentiation is required after meiosis II |
8. The sperm formed are motile. | 8. The ovum or egg is non-motile. |
Question 9.
a) Draw a neat labelled diagram of sectional view of seminiferous tubule.
b) Explain the mechanism of parturition with the help of fetal ejection reflex.
Question 10.
What is spermatogenesis? Explain with a schematic representation.
Answer:
Formation of haploid sperms from the diploid spermatogonial cells of the testes is called spermatogenesis. Primordial germ cells give rise to spermatogon ial cells and sertoli cells. It is the spermatogonial cells that develop into the spermatozoa. Spermatogenesis involves four phases.. viz..
a. Multiplication Phase
b. Growth Phase
e. Maturation Phase
d. Spermiogenesis
(a) Multiplication Phase: The diploid spermatogonial cells of the seminiferous tubules divide repeatedly by mitosis to form more spermatogonial cells. Among them only a few will enter into growth phase and others are kept in reserve.
(b) Growth Phase: Spermatogonial cells obtained from multiplication phase grow in size, however they still remain diploid. These cells are now called primary spermatocytes.
(c) Maturation Phase: This phase involves two successive divisions, viz., Meiosis I and Meiosis H. The meiosis is reductional and two haploid cells are formed from each primary spermatocyte. The resultant cells of I melotic division are called secondary spermatocytes. These secondary spermatocytes undergo meiosis II which is equational. As a result each secondary spermatocyte produces two haploid cells of equal size called spermatids. Hence, four haploid spermatids are formed during maturation phase from each diploid primary spermatocyte.
(d) Spermiogenesis: Sjrmatids are not gametes. they are ordinary haploid cells. During spermiogenesis or spermateliosis each spermatid in association with sertoli cells become tadpole like, flagellated and highly motile gamete called spermatozoan or sperm.
Hormonal Control of Spermatogenesis:
- Spermatogenesis is initiated due to an increase in the secretion of gonadotropin-releasing hormone (GnRH) by the hypothalamus at the age of puberty.
- The increased levels of GnRH act on the anterior pituitary and stimulate the secretion of two gonadotropins, i.e., luteinizing hormone (LH) and folilcie stimulating hormone (FSH).
- LH acts on the Leydig cells and stimulates them to secrete testosterone.
- FSH acts on the Sertoli cells and stimulates secretion of some factors, which help in spermiogenesis.
Oogenesis:
The formation of ova or eggs from the diplod oogonial cells of the ovary is called oogenesis. Primordial germ cells give rise to oogoñial cells, and follicular cells (nurse cells). It is the oogonial cells that develop into ova. Oognesis involves three phases, viz.,
1. Multiplication phase
2. Growth phase
3. Maturation phase
1. Multiplication phase: The diploid oogonial cells of the ovarian follicles divide repeatedly by mitosis to produce more oogonial cells. Among them only a few will enter into growth phase and others are kept in reserve.
2. Growth phase: During this phase few oogonial cells synthesise yolk or vitelline in the cytoplasm and transform into primary oocytes. Hence this phase is also called vitellogenesis. During the growth of oogonial cells into primary oocytes. follicular cells or nurse cells or granulosa cells assist vitellogenesis.
3. Maturation phase: This phase involves two successive divisions namely meiosis I and meiosis II. The meiosis I is a reductional cell division resulting in the formation of a smaller cell often called the first polar body and higher secondary oocyte. The larger secondarý oocyte undergoes meiosis II to form a larger cell called ootid or ovum and a smaller cell called as second polar body. The first polar body may also undergo meiosis II to produce two more secondary polar bodies. So at the end of oogenesis one ovum and three polar bodies are formed. These polar bodies will not survive. They undergo disintegration.
Question 11.
What is menstrual cycle? Describe the different phases in it.
Answer:
Menstruation:
It ¡s a normal female periodic cycle of discharge of blood due to rupturing of endometrium of uterus. The period of menstruous cycle is about 28 days. The menstruous cycle may be divided into four phases.
1. Menstrual Phase: It is also called menses. It is a normal female periodic cycle of discharge of blood due to rupturing of endometrium of uterus. Also unfërtilised egg and ruptured tissue of endometrium is discharged. It lasts for about five days of the cycle.
2. Pre ovulatory Phase I Follicular phase (Proliferative phase) : Here regeneration and thickening of endometrium of the uterus occurs. Also this phase is charäcterized by the transformation of primary follicle into mature Graafian follicle under the influence of FSH. The secretion of gonadotropins (LH and FSH) increases gradually during the follicular phase. It takes about 6 to 13 day in a 28 day cycle.
3. Ovulation / Luteal phase (Secretory phase): During this process ovum is released from ovary in the pelvic cavity and the process is called ovulation. it occurs approximately on 14th day of menstrual cycle. It is a phase in which both LH and FSH are at the peak level and there is an LH surge.
4. Post Ovulation Phase: It ¡s also known as lutcal phase. It lasts from 15h to 28 in a menstrual cycle. After ovulation. LII stimulates the development of corpus luteum which starts secreting progesterone prepares the endometrium of the uterus to receive the fertilized ovum. However, if fertIlization does not occur the corpus lutcum degenerates and becomes the corpus albicans.
Note: Menarche: The first menstruation begins at puberty and is called menarche. It starts at
puberty between the age of 12 to 15 years.
Menopause: In human beings, nìenstrual cycles ceases aroúnd 50 years of age; that is termed as menopause. Menopause results due to the decline in the production of estrogen and progesterone from the ovary.