RBSE Class 12 Biology Chapter 31- Gametogenesis in Human. In this chapter, students can learn in detail about spermatogenesis, the formation of spermatids, the formation of spermatocytogenesis, the structure of human sperm, oogenesis and an egg of a mammal. It also deals with the process of oogenesis, differentiation of spermatid, cell organelles involved in the formation of sperm, the process of spermatogenesis and a lot more.
These important questions help students to perform exceptionally well in their exams. By practising these important questions, students can analyze their preparation, get a thorough knowledge about all the important terminologies and perform their best in the examinations.
RBSE Solutions for Class 12 are the best study material for both class assignments and other board examinations. By practising these important questions, students can gain deep knowledge about the topics explained in this chapter and also help them to be well prepared for their upcoming examinations.
RBSE Class 12 Biology Chapter 31 Important Questions
RBSE Biology Chapter 31: MCQ Type Questions
Q.1. In which process the polar body is formed?
(a) Regeneration
(b) Spermiogenesis
(c) Fertilization
(d) Oogenesis
Sol: (d) Oogenesis.
Q.2. How many ova are produced from one primary oocyte?
(a) One
(b) Two
(c) Four
(d) Eight
Sol: (a) One.
Q.3. An arrangement of fibrils in the tail of the sperm is _________.
(a) 9 singlet + 2 doublet
(b) 9 singlet + 9 doublet
(c) 9 doublet + 2 singlet
(d) 9 singlet + 9 doublet +2 singlet
Sol: (d) 9 singlet + 9 doublet +2 singlet.
Q.4. The process of ova formation is called _________.
(a) Ovipary
(b) Oogenesis
(c) Ovulation
(d) Gametogenesis
Sol: (b) Oogenesis.
Q.5. Releasing the mature ovum from an ovary is called _________.
(a) Implantation
(b) Fertilization
(c) Ovulation
(d) Parturition
Sol: (c) Ovulation.
Q.6. How long does sperm last inside a woman vagina?
(a) 1 to 2 days
(b) 3 to 4 days
(c) 5 to 10 days
(d) 7 to 14 days
Sol: (a) 1 to 2 days.
Q.7. In mammalian sperm, the shedding of an acrosomal membrane is called _________.
(a) Activation
(b) Agglutination
(c) Capacitation
(d) Fertilization
Sol: (c) Capacitation.
Q.8. Which of the following is immortal?
(a) Glomerular cell
(b) Germ cell
(c) Somatic cell
(d) Pituitary cell
Sol: (b) Germ cell.
Q.9. Which phase of sperm development does not participate in the ovum development?
(a) Growth phase
(b) Spermiogenesis
(c) Multiplication phase
(d) Formation of the polar body
Sol: (b) Spermiogenesis.
Q.10. Oogenesis has _________.
(a) Growth phase
(b) Maturation phase
(c) Multiplication phase
(d) All of the above
Sol: (d) All of the above.
RBSE Biology Chapter 31: Short Answer Type Questions.
Q.1.Which cell do organelles participate in the formation of the middle part of the sperm?
Sol: Mitochondria and the centrosomes are the two main cell organelles involved in the formation of the middle part of the sperm.
Q.2.Which part of the sperm comes in contact with the egg at the time of fertilization?
Sol: Acrosome is the apical part of the sperm’s head, which comes in contact with the egg at the time of fertilization.
Q.3. What kind of eggs are found in the placental mammals?
Sol: Alecithal is a type of egg found in the placental mammals.
Q.4. What are spermatids?
Sol: Spermatids are the group of cells formed as a result of the second maturation division during the process of spermatogenesis, which gives rise to four spermatids.
Q.5. Where is the Barr body found?
Sol: The Barr body, also called the sex chromatin are found within the nucleus of every somatic cell in females.
Q.6. Why are sperms produced in quantity in comparison to eggs?
Sol: During the process of spermatogenesis four sperms are formed, while in the process of oogenesis only one ovum is produced per one oogenesis.
Q.7. Which hormone is found on the surface of an egg?
Sol: Gynogamone and Fertilizin are the two main hormones found on the surface of an egg.
Q.8. What is Zygote?
Sol: A zygote is a fertilized ovum. The germ cells undergo meiosis to reach a haploid state(n) as part of spermatogenesis and oogenesis. The sperm and the unfertilized ovum reinstates a chromosome set in zygote in a diploid state(2n).
Q.9. What is oogenesis?
Sol: Oogenesis is the process of formation of female gametes. It is the type of gametogenesis through which ova or the female gametes are formed, and this female gamete is known as an ovum.
Q.10. What are germ cells?
Sol: Germ cells are a central component of sexual reproduction in all sexual reproducing living organisms. The germ cells differentiate to produce male and female gametes, sperm and unfertilized eggs and undergo meiosis to produce a haploid set of chromosomes. These cells are immortal cells
Q.11.What is the Barr body.?
Sol: The inactive X chromosome in the female somatic cells is known as a Barr body. These Barr bodies are not involved in sexual reproduction. The Barr bodies are also sometimes called the sex chromatin.
Q.12. What is Gametogenesis?
Sol: Gametogenesis is the process of division of haploid or diploid cells to produce new haploid cells. In humans, two different types of gametes are present. Male gametes are called sperm and female gametes are called the ovum.
Q.13. What is spermatogenesis?
Sol: Spermatogenesis is a process of developing male gametes, known as sperm within the male reproductive organs, the testes. During the process of spermatogenesis, four spermatids are produced which are functional and that later develops into spermatozoa.
Q.14.What is an Ovulatory phase?
Sol: It is the phase of the menstrual cycle. It is the mid-cycle phase, in which ovulation takes place, which begins after day 12 and in between the day 13 to day 17. The end of the follicular phase along with the ovulation period defines the fertilization period.
Q.15.What are menstrual hormones?
Sol: The entire process of the menstrual cycle is controlled by the endocrine system and the hormones involved are estrogen, progesterone, FSH and LH are the main female hormones involved in the variation and regulation of the menstrual cycles in all women.
Q.16. What is the luteal phase?
Sol: Luteal phase is the post-ovulation phase of the menstrual cycle. In this phase, the fate of corpus luteum is decided. If fertilization occurs, pregnancy starts. If fertilization doesn’t occur, it marks the onset of another cycle.
Q.17. How is a primary oocyte different from a secondary oocyte?
Sol: The primary oocyte is a diploid cell whereas secondary oocyte is a haploid cell. The primary oocyte is formed when oogonia are at the prophase-I of the meiotic division in the foetal ovary whereas secondary oocyte is formed from primary oocyte after meiosis – I division to produce ova in females during the stage of puberty.
Q.18. What are the stages of Oogenesis?
Sol: The process of oogenesis has three stages. They are as follows:
- Pre-natal Stage
- Antral Stage
- Pre-Ovulatory Stage.
Q.19.What is menopause?
Sol: Menopause is when the menstruation cycle comes to a halt, indicating the end of the fertile period as the process of ovulation stops.
Q.20. What is fertilization?
Sol: Fertilization is the biological process of fusion of both male and female gametes resulting in the formation of a zygote. In humans, the fertilization process takes place in the fallopian tube.
RBSE Biology Class 12: Long Answer Type Questions
Q.1. What is the difference between oogenesis and spermatogenesis?
Sol: Oogenesis and spermatogenesis are the processes of formation of male and female gametes. Spermatogenesis helps in the formation of sperms and oogenesis helps in the formation of ova.
The differences between the oogenesis and spermatogenesis are:
| Oogenesis | Spermatogenesis |
| Production of eggs from oogonia. | Production of sperm from spermatogonia. |
| Takes place inside the ovary in females. | Takes place inside the testes in males. |
| All except the last phase takes place inside the ovary. | All phases occur inside the testis. |
| Early stages observed during the fetal period. Rest stages observed between puberty and menopause. | A continuous process that is initiated from puberty and lasts until death. |
| Matured from germinal epithelium overlying the ovary. | Developed from the germinal epithelial lining of the seminiferous tubules. |
| Sertoli cells not found in germinal cell epithelium. | Sertoli cells found in germinal cell epithelium. |
| Few oogonia divide to produce eggs, one at a time. | Spermatogonia are divided by meiosis to produce sperms. |
| The growth phase of oogonia is lengthy. | The growth phase of spermatogonia is short. |
| Generates non-motile gametes. | Produces motile gametes. |
| Primary oocyte divides to form a secondary oocyte and polar body during meiosis-I. | During meiosis-I, primary spermatocytes divide to form two secondary spermatocytes. |
Q.2. Draw a schematic diagram of oogenesis.
Sol: The schematic diagram representing oogenesis in the female reproductive system.
Q.3. Explain the process of spermatogenesis.
Sol: The process of spermatogenesis in the male reproductive system takes place in four different stages:
Stage 1:
The Diploid spermatogonia are situated in the seminiferous tubules which include twice the total number of chromosomes. This replicates mitotically in interphase before the method of meiosis 1 to create 46 pairs of sister chromatids.
Stage 2:
In this, the chromatids allow the exchange of genetic information through the synapsis process. It is done before dividing into haploid spermatocytes through meiosis.
Stage 3:
In this division, the new two daughter cells will further divide into 4 spermatids, having unique chromosomes that are approximately half in number to the original spermatogonium.
Stage 4:
In this stage, the cells move from the lumen of the testes to the epididymis. They mature and develop into four sperm cells with the growth of microtubules on the centrioles to develop an axoneme. The remaining centrioles elongate and develop into sperm tail.
Q.4. What is Oogenesis? Draw a neat labelled diagram showing the process of Oogenesis.
Sol: Oogenesis is the process of formation of female gametes. This process begins inside the fetus before birth. The steps in oogenesis up to the production of primary oocytes occur before birth. Primary oocytes do not divide further. They either become secondary oocytes or degenerate. Oogenesis occurs in the outermost layers of the ovaries. Oogenesis starts with a germ cell called oogonium and undergoes mitosis to increase in number.
The process of Oogenesis.
Q.5. Describe the structure of human sperm.
Sol: Structure of Human Sperm:
The male gamete is called a spermatozoon or a sperm. It is a single cell structure and it bears a haploid set of chromosomes within the nucleus.
The human sperm comprises a head, neck, middle piece and tail.
Head
It is the anterior part of the sperm, whose shape varies from species to species. The anterior part of the head is occupied by the acrosome, which is formed by the Golgi body and it is bounded by a unit membrane. It comprises sperm lysins and is involved in the process of fertilization. There is a nucleus just behind the acrosome, which is slightly elongated and its posterior end has a notch.
The nucleus has a haploid set of chromosomes, which consists of protamines in addition to the DNA. The sperms of some species have a vacuole -like structure between the acrosome and the nucleus, which is called the perforator.
The posterior position of the nucleus protects the proximal centriole, which is to be contributed to the egg at the time of fertilization.
It helps at the beginning of the first cleavage.
Neck
It is a small part, which connects the head to the mid-piece. It comprises a distal centriole, which remains at 90° to the proximal centriole. This distal centriole produces an axial filament that extends throughout the length of midpiece and the tail. It exhibits a fibrilar arrangement of 9 doublets + 2 singlets.
Middle-piece
In the middle piece, the axial filament is surrounded by a sheath called manchette. The manchette is made up of a nebenkern and the little condensed cytoplasm. In the sperm of some species, the posterior end of the middle place may have a ring called centriole.
Tail
In the tail, the axial filaments are covered by a sheath, which is composed of 9 singlet fibres. This sheath is absent around the terminal end of the tail. The whole sperm is bounded by a plasmalemma. Most of the sperms are mono-flagellated.
Structure of Human Sperm
Q.6. Describe the formation of Acrosome.
Sol: Acrosome is the apical part of the sperm’s head, which comes in contact with the egg at the time of fertilization.
Formation of Acrosome
The anteriormost part of the sperm is called an acrosome. It is formed by the Golgi body during the process of spermiogenesis.
At first, one of the vacuoles of the Golgi body develops an acrosomal granule, which gradually accumulates lytic enzymes and forms a cap-like structure on the anterior end of the nucleus.
Later, this cap-like structure gets bound by a single unit of the plasma membrane and forms an acrosome.
The remaining parts of the Golgi body are lost in the form of Golgi, rest along with some cytoplasm.
Q.7. Draw a schematic diagram of spermatogenesis.
Sol: The schematic diagram representing spermatogenesis in the male reproductive system.
Q.8. Write a brief note on the three stages of gametogenesis.
Sol: Gametogenesis includes spermatogenesis and oogenesis. It includes three phases:
Multiplication phase
The phase in which the diploid germ cell divides by mitosis and forms diploid oogonia in oogenesis and spermatogonia in spermatogenesis.
Growth phase
This phase involves only the growth in size. It is the longest phase and results in the formation of the primary oocyte in oogenesis and primary spermatocyte in spermatogenesis.
Maturation phase
This phase involves meiosis division and it is divided into two phases:
- Maturation – I
In this phase, the spermatocyte or diploid primary oocyte is divided by meiosis-I and haploid secondary spermatocytes are produced in spermatogenesis. In oogenesis, one secondary oocyte and one polar body is formed.
- Maturation – II
In spermatogenesis, the two secondary spermatocytes are divided by meiosis-II and four haploid spermatids are produced, which is finally converted into four haploid sperms.
In oogenesis, the secondary oocytes are divided by meiosis-II and one haploid ootid and one haploid polar body-II are formed.
Q.9. Explain the process of oogenesis.
Sol: Process of Oogenesis in the female reproductive system takes place in three different stages:
Pre-natal Stage
In this stage, the primary oocyte grows while being arrested in meiosis-I. The follicular cells proliferate and form a stratified cuboidal epithelium. Such cells are known as granulosa cells. These cells secrete glycoproteins to form zona pellucida around the primary oocyte.
Antral Stage
The fluid-filled spaces between granulosa cells combine to form a central fluid-filled space called the antrum. These are known as secondary follicles. In every month cycle, these secondary follicles develop under the influence of follicle-stimulating hormone and luteinizing hormone.
Pre-Ovulatory Stage
This stage is induced by LH surge, and meiosis-I completed here. Two haploid cells of unequal sizes are formed within the follicle. One of the daughter cells that receive less cytoplasm forms a polar body. This cell does not participate in ovum formation. The other daughter cell is known as the secondary oocyte. The two daughter cells undergo meiosis-II. The polar body replicates to form two polar bodies, while the secondary oocyte arrests in the metaphase stage of meiosis-II.
Q.10. What is spermatogenesis? Draw a neat labelled diagram showing the process of spermatogenesis.
Sol: Spermatogenesis is a process of developing male gametes, known as sperm within the male reproductive organs, the testes. During the process of spermatogenesis, four spermatids are produced which are functional and that later develops into spermatozoa.
Process of Spermatogenesis in the male reproductive system
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