Class 12 Biology Chapter 3 Human Reproduction The answer to each chapter is provided in the list so that you can easily browse through different chapters Assam Board HS 2nd Year Biology Chapter 3 Human Reproduction Question Answer.
Class 12 Biology Chapter 3 Human Reproduction
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Human Reproduction
Chapter – 3
REPRODUCTIONS
Very Short Answer Type Questions
Q.1. The process of formation of gametes is called_____
Ans : Gametogenesis.
Q.2. The testes in mammal are situated outside the abdominal cavity within a pouch called ____
Ans : Scrotum.
Q.3. The process of release of ovum from mature follicle is called ____
Ans : Ovulation.
Q.4. Ovulation is induced by hormone called ____
Ans : LH or luteinizing hormone.
Q.5. The fusion of a male and female gamete is called____
Ans : Fertilization.
Q.6. Secondary spermatocytes are formed from_____ by first meiotic division.
Ans : Primary spermatocytes.
Q.7. Zygote divides to form ____ which is implanted in uterus.
Ans : Embryo.
Q.8. The structure which provides connection between foetus amd uterus of the mother is called____
Ans : Placenta.
Q.9. The process which transform zygote to blastula is called _____
Ans : Cleavage.
Q.10. Gestation period of human female is_____
Ans : 9 months. (270 days)
Q.11. Cessation of menstrual cycle in a female is called____
Ans : Menopause.
Q.12. Progesterone is secreted by____
Ans : Corpus luteum.
Q.13. The secretory phase of menstruation cycle is also called the ____
Ans : Luteal phase.
Q.14. Each ovary is connected to the pelvic wall and uterus wall by _____
Ans : Ligament.
Q.15. Acrosome of sperm is formed from the ____
Ans : Golgi Body.
Q.16. ____ is an example of viviparous animal.
Ans : Mammal (man monkey etc)
Q.17. Union of male gamete and the female gamete is called ____
Ans : Fertilization.
Q.18. The function of the sertoli cell is to provide nutrition to the ____ cells.
Ans :Germ cells or spermatozoa.
(B). True or False :
Q.1. Humans are ovoviviparous.
Ans : False.
Q.2. Leydig cells are present in the interstitial spaces between the seminiferous tubules.
Ans : True.
Q.3. The funnel shaped part of the fallopian tube close to ovary is called isthmus.
Ans : False
Q.4. The secondary spermatocytes- contain haploid chromosome.
Ans : True.
Q.5. Spermatogonia undergo mitotic division.
Ans : True.
Q.6. GnRH is an anterior pituitary hormone.
Ans : False.
Q.7. The primary ovarian follicle is also called Graffian follicle.
Ans : False.
Q.8. XY sex chromosomes are found in human male.
Ans : True.
Q.9. Blastocyst is formed from the morula.
Ans : True.
Q.10. Acrosome is found in female gamete.
Ans : False.
(C). Very Short Answer Questions :
Q.1. State the difference in reproductive age of man and woman.
Ans : There äre a remarkable difference in the reproductive age of man and woman i.e. in male sperm formation continues even in old but in females the formation of ovum ceases around the age of fifty year.
Q.2. What is urethral meatus?
Ans : In males the urethra originates from the urinary bladder and extends through the penis to its external opening called urethral meatus.
Q.3. Name two male accessory glands.
Ans : A paired seminal vesicles and a paired bulbourethral glands.
Q.4. State the components of seminal plasma.
Ans : The components of seminal plasma includes rich fructose, calcium and certain enzymes secretions of male accessory glands constitute the seminal plasma.
Q.5. Define spermiation.
Ans : After the formation of sperms by the process of spermiogenesis, sperm heads become embedded in the sertoli cells and are finally released from the seminiferous tubules by the process called spermiation.
Q.6. What is the function of acrosome?
Ans : Acrosome, the cap like anterior portion of the sperm head is filled with enzymes that helps in the fertilization of the ovum.
Q.7. Why sperm contains mitochondria?
Ans : The middle pices of sperm contains numerous mitochondria, which produce energy for the movement of tail that facilitate sperm motility essential for fertilization.
Q.8. Name the hormones which maintain the functions of the male sex accessory ducts and glands.
Ans : Androgen.
Q.9. What is Semen?
Ans : The seminal plasma along with the sperms constitute the semen.
Q.10. Why human female has fixed number of primary follicle in the ovary?
Ans : Oogenesis is initiated during the embryonic development stage in females where a couple of million of oogonia are formed in the fetal ovary and no more oogonia are formed after birth. So females have a fixed number of follicle in ovary.
Q.11. What do you understand by ovulation?
Ans : The process of release of the secondary oocyte from the ovary by rupturing the Graffian follicle is known as ovulation.
Q.12. Define menstrual cycle.
Ans : The reproductive cycle in the female primates like monkeys, apes and human being is called menstrual cycle.
Q.13. How the corpus luteum is formed?
Ans : After ovulation the luteal phase starts where the remaining parts of the Graffian follicle transform as the corpus luteum.
Q.14. What happens to corpus luteum in absence of fertilization?
Ans : In absence of fertilization the corpus luteum degenerates.
Q.15. Define menopause.
Ans : The ceasing of the menstrual cycle at a particular age is known as menopause.
Q.16. Name the secretion of corpus luteum.
Ans : The recreation of the corpus luteum is known as proges terone which is a hormone.
Q.17. What is fertilization?
Ans :The process of fusion of sperm of male with the ovum of a female is known as fertilization.
Q.18. You studied the chromosome of a human and found that there present two identical sex chromosomes. What will be the sex of the individual?
Ans : As there found two identical sex chromosome so the sex of the individual will be female.
Q.19. How many sex chromosome is present in the sperm?
Ans : Sperm contains haploid number i.e. half the number of chromosome present in the organisms somatic cells.
Q.20. What are two layers of cells found in the blastocyst.
Ans : The outer layer of the blastocyst is called trophoblast and the inner is inner cell mass.
Q.21. Name an organ which is formed of tissues of two different individuals.
Ans : Placenta.
(D) Short Answer Questions (Two Marks Each):
Q.1. What is the significance of presence of testes within scrotum?
Ans : The scrotum helps in maintaining the low temperature of testes which is 2-2.5°C lower than the normal internal body temperature of necessary for spermatogenesis.
Q.2. Write the functions of two types of cells found within the seminiferous tubule.
Ans : The two types of cells found within the seminiferous tubules are:
(i) Male germ cells that gives rise to sperm.
(ii) Sertoli cells which provide nutrition to germ cells.
Q.3. Name the different events of reproduction occur in human.
Ans : The different events of reproduction occur in human are :
(i) Formation of male and female gametes.
(ii) Transfer of sperms into the female genital tract.
(iii) Fusion of male and female gametes.
(iv) Formation and development of blastocyst.
(v) Implantation.
(vi) Gestation.
(vii) Parturition.
Q.4. What is Leydig cell? State its function.
Ans : The regions outside the seminiferous tubule is called interstitial spaces that contain small blood vessels and interstitial cells or leydig cells. Leydig cells synthesise and secrete testicular hormones called androgens.
Q.5. State the function of FSH and LH.
Ans : (i) Follicular stimulating hormone (FSH) acts on the sertoli cells and stimulates secretion of some factors which help in the process of spermiogenesis.
(ii) Luteinizing hormone (LH) acts at the leydig cells and stimulates synthesis and secretion of androgens which in turn stimulate the process of spermatogenesis.
Q.6. State the structure of sperm head.
Ans : A sperm is a microscopic structure composed of a head, neck, a middle piece and a tail. The sperm head contains and elongated haploid nucleus, the anterior portion of which is covered by a cap like structure, acrosome. The acrosome is filled with enzymes that help fertilization of 6. the ovum.
Q.7. Why unequal division of cytoplasm occurs during formation of ovum?
Ans : In the process of oogenesis the primary oocyte within the tertiary follicle grows in size and completes its first meiotic division. This division is unequal and results in the formation of a large haploid secondary oocyte and a tiny first polar body. The secondary oocyte retains bulk of the nutrient rich cytoplasm of the primary oocyte.
Q.8. What are the changes that occurred during follicular phase of menstrual cycle in human female.
Ans : The second phase of the menstrual cycle is the follicular phase. During this phase, the primary follicles in the ovary grow to become a fully mature Graffian follicle and simultaneously the endometrium of uterus regenerates through proliferation. These change in the ovary and the uterus are induced by changes in the levels of pituitary and ovarian hormones.
Q.9. Differentiate between menarche and menopause.
Ans :
| Manche | Menopause | ||
| (i) | The first menstruation that begins of puberty is known as Menarche. | (i) | The cessation of menstrual cycle at a particular time period is known as menopause. |
| (ii) | It starts at an age of 10-12 years. | (ii) | It occurs at 50-55 age. |
Q.10. State the functions of progesterone.
Ans :The progesterone hormone secreted by corpus luteum is very much essential for maintenance of the endometrium. Endometrium is necessary for implantation of the fertilized ovum and other events of pregnancy.
Q.11. How implantation of human embryo occurs in the mother uterus?
Ans : After the formation of the blastocyst and the trophoblast layer of the blastocyst gets attached to the endometrium and the inner cell mass gets differentiated as the embryo. After attachment, the uterine cells divide rapidly and covers the blastocyst. This become embedded in the endometrium of the uterus which is known as implementation.
Q.12. State the functions of placenta.
Ans : After implementation, finger placenta appear on the trophoblast which plays an important role during pregnancy. The placenta facilitate the supply of oxygen and nutrients to the embryo and also removal of carbon di oxide and excretory or waste mate rials produced by the embryo. The placenta is connected to the embryo through an umbilical cord which help in the transport of substances to and from the embryo. It also plays as an endocrine gland of secretion different hormones.
Q.13. How placenta is formed?
Ans : After implementation, a finger like projections appear on the trophoblast called chorionic villi which are surrounded by the uterine tissue and maternal blood. This chorionic villi and uterine tissue become interdigitated with each other and jointly form a structural and functional unit between developing embryo and maternal body called placenta.
Q.14. What are Stem cells? Where they are found?
Ans: Stem cells are those cells which have the potency to give rise to all the tissues and organs.
These are found in the inner cell mass of the blastocyst.
Q.15. Why breast-feeding during initial period of infant growth is recommended?
Ans :The milk produced during the initial few days of lactation is called colostrum which contains several antibodies absolutely essential to develop resistance for the new born babies. Breast feeding during the initial period of infant growth is recommended by doctors for bringing up a healthy baby.
Q.16. Describe the luteal phase of the menstrual cycle.
Ans : Luteal phase is also called as progestational or premenstrual or secretory or post ovulatory phase. It lasts for about 12-14 days and extends from 16th th 28th day of the menstrual cycle.
It is characterised by the following changes :
(i) Corpus luteum (yellow body) formed from empty graafian follicles, increases in size, so called luteal phase.
(ii) Corpus luteum secrets progesterone hormone whose level in blood gradually increases and in duces the following changes:
(a) Decreases the secretion of FSH and LH from the anterior pituitary so inhibits the maturation of follicle and ovulation.
(b) Uterine endometrium further proliferates and ready for implantation.
(c) Reduces the uterine movements.
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