Human Reproduction Important Questions

CBSE Class 12 Biology Human Reproduction Important Questions have been provided in this article along with detailed solutions. The important questions have been formulated as per the latest CBSE Board Curriculum that would assist the students to understand all the important topics covered in the chapter like Human Reproductive System, Process of Reproduction, Gametogenesis, Oogenesis, Pregnancy, Fertilization, Menstrual Cycle, etc. 

Human Reproduction refers to the process through which humans give birth to their young ones which involves internal fertilization by sexual intercourse. Humans are viviparous creatures and reproduce sexually. Fertilisation in humans consists of a variety of events, which include- Gametogenesis (spermatogenesis for the formation of sperms in males; and oogenesis for the formation of the ovum in females), formation of the zygote, different phases of embryo development before parturition. 

Human Reproduction

Read More: Sexual Reproduction

---

Very Short Answer Questions (1 Mark Questions)

Ques. Enlist the different phases of events as observed during the human reproduction cycle.

Ans. Following is the sequence of events occurring in the process of human reproduction:

1. Gametogenesis
2. Insemination
3. Fertilization
4. Implantation
5. Gestation
6. Parturition

Ques. Why does the failure of testes to descend in the scrotal sac lead to sterility?

Ans. The high temperature of the abdomen is sometimes responsible to kills the spermatogenic tissues, which leads to the failure of the testes to descend into the scrotal sac.

Ques. Why does a female not undergo menstruation during her pregnancy?

Ans. All events involved during menstruation in a female are halted during pregnancy, as the egg released is now fertilized. Whereas, menstruation only occurs when the egg is not fertilized.

Ques. Write the number of sperms produced by a primary spermatocyte.

Ans. 40 sperms are produced by a primary spermatocyte.

Ques. How many eggs will be produced by a primary oocyte?

Ans. 10 eggs are produced by a primary oocyte.

Ques. Mention the functions that are carried out by the respective female reproductive organs:

• Ovaries
• Oviduct
• Vagina
• Uterus

Ans. The functions are as follows:

1. Ovulation
2. Fertilization
3. Birth
4. Pregnancy

Ques. What is the main hormone that is secreted during childbirth?

Ans. Oxytocin hormone is secreted during childbirth.

Ques. Where do the sperm and ovum meet?

Ans. The sperm and the ovum meet at the ampulla-isthmus junction of the fallopian tube.

Read More: Male and Female Reproductive Organs

---

Short Answer Questions (2 Marks Questions)

Ques. Why do the testes remain suspended from the scrotum outside the abdomen?

Ans. The formation of spermatocytes is not possible at the human body temperature. The process of spermatogenesis and the seminiferous tubules involves a temperature slightly lower than the human body temperature. Hence, the scrotum lies in the cavity outside the abdomen.

Ques. Explain the different parts of the sperm with a diagram.

Ans.  The sperm is the male gamete that consists of a head, neck, middle piece, and tail. The parts of sperm are bounded by a plasma membrane.

The head consists of a haploid nucleus. The front part of the head is protected by a cap-like structure called the acrosome. The acrosome is filled with enzymes that help in reaching the ovum and cause fertilization.

Structure of Sperm

The main parts of the sperm are as follows:

• Head: The head contains the nucleus. The nucleus has the DNA of the cell. It helps the sperm to break through the membrane of an egg.
• Middle Piece: The mid part of the sperm is filled with mitochondria, for producing the energy to swim with the semen.
• Tail: The tail paddles and helps the sperm to move. This tail helps to push the sperm forward.

Ques. What is the function of the placenta?

Ans. The placenta develops in the uterus during the gestation period. The placenta is the provider of nutrition and oxygen for the embryo. The growing baby is connected to the placenta via an umbilical cord. It also helps the embryo to excrete waste and carbon dioxide. It is attached to the wall of the uterus, functioning as an endocrine tissue, and regulating hormones.

Ques. Draw the schematic diagram representing the oogenesis process.

Ans. A schematic diagram representing the oogenesis process is as follows: 

Ques. Write the difference between Graafian follicle and corpus luteum.

Ans. The difference between the Graafian follicle and corpus luteum is tabulated below: 

Ques. What is the significance of fertilization?

Ans. The significance of fertilization can be described as follows: 

• The diploid number of chromosomes is again formed after the fusion of the haploid male and female gamete.
• The secondary oocyte is activated and matured to give rise to the ovum cleavage and segmentation is initiated.

Read More: Difference between Haploid and Diploid

---

Long Answer Questions (3 Marks Questions)

Ques. What changes are observed in the primary follicle while it transforms into the Graafian follicle?

Ans. Cells are formed within the ovary in the oogonia. After birth, oogonia are not formed. The cells enter into the Prophase-I stage of the Meiotic Division. These primary oocytes attach themselves by a layer of granulosa cells for the formation of the primary follicle which degenerates during the stages of birth to puberty. The primary follicles are surrounded by extra layers of granulosa cells and a new theca known as secondary follicles. 

The theca is split into other theca externa and an inner theca interna which secretes oestrogen. The secondary follicle transforms into a tertiary follicle distinguished by an antrum. It is a fluid-filled cavity. Now, the primary oocyte grows in size inside the tertiary follicle to finish the first meiotic division. Finally, the tertiary follicle transitions to form the Graafian follicle.

Ques. Describe the main function of the testes and the ovaries in reproduction.

Ans. The testes are the male reproductive organ. It is located in the sac-like scrotum, in the cavity outside the abdomen. It produces sperms and the male hormone testosterone.

The female reproductive organ is called the ovaries. It is responsible for the secretion of two hormones- oestrogen and progesterone. It also produces the egg, which when fertilised with the sperm forms the zygote.

Ques. Differentiate between spermatogenesis and oogenesis.

Ans. The difference between spermatogenesis and oogenesis is tabulated below:

Read More: Female Reproductive System

Ques. Explain the statement: “A fertile egg is the blueprint of future development.”

Ans. The genetic information inside a sperm carries the DNA of the male, who becomes the father. This DNA has 23 chromosomes (represented as XY, the male sex chromosome). Although, the mother is responsible for the secretion of the egg, which also has the genetic information from the mother’s side. This sex chromosome has 23 chromosomes (represented as XX).

When fertilization occurs, the infusion of the male and female gametes takes place and a new genetic combination is formed. The zygote will contain this variation of the genetic combination, and hence control the development of the embryo.

Read More: Human Development, Pregnancy Stages, Embryogenesis

---

Very Long Answer Questions (5 Marks Questions)

Ques. Draw and explain in detail the female reproductive system. Also, mention the functions of each part.

Ans. The female reproductive system is positioned in the lower pelvic region. It consists of the ovaries, the oviduct, uterus, cervix, vagina and the external genitals. The female reproductive system has to provide for ovulation, fertilization, gestation, and parturition.

Female Reproductive System

• Ovaries: Ovaries are a pair which contain germ cells. These germ cells mature to form follicles and the egg. It is also responsible for releasing one egg every month for menstruation, in case the egg is not fertilized.
• Fallopian Tubes: The egg released enters the fallopian tube through the ostium. There are finger-like projections, called fimbriae. The fallopian tube has three segments- the infundibulum, ampulla and isthmus. The ampulla junction is the site of fertilisation of the egg and the sperm.
• Uterus: It is the sac-like structure in the lower abdomen of the female body. There are three linings of the uterus- the endometrium, myometrium, and perimetrium. The lining of the cell proliferates during the process of implantation. This structure is involved in the implantation of the foetus. The sac holds the developing embryo during gestation.
• Cervix: It is located in the lower region of the uterus. The cervix allows the penetration of the penis and receives the sperm.
• Vagina: This is the tube-like region which gets open in the outer region of the female body through the vulva. This is basically the region through which the sperms move towards the egg for fertilisation and it is also called the birth canal through which the child comes out.

Ques. Explain the entire menstruation process, with respect to the roles of FSH, LH, oestrogen, and progesterone.

Ans. Menstruation is a process in which the endometrial layer and lining of muscles are released along with the blood. This happens when the egg which is released every month is not fertilised. The cycle of menstruation starts on the 28th day.

During this cycle, the ovary undergoes the influence of hormones.

• Menstrual Phase: In this phase, the lining of the uterus breaks down as a result of lower secretion of LH, FSH, oestrogen and progesterone.
• Follicular Phase: the release of FSH and LH is higher, which triggers the release of oestrogen. FSH is responsible to control the follicular phase and stimulating the follicles.
• Ovulatory Phase: The level of LH is at its peak, which is known as the LH surge. It activates and ruptures the mature Graafian follicles, thereby releasing the ovum.
• Luteal Phase: The secretion of the LH and FSH hormones decreases. After the ovulation period, the follicle ruptures, and it begins to transform into the corpus luteum. Then, this secretes large quantities of progesterone.

Ques. Explain with a diagram, the mammary gland in females.
Ans. Mammary glands in females are accessory glands. It is a layer of fat stored in the breasts. This gland has 15-20 lobes in each breast. These glands are responsible for secreting milk and are called alveoli. The milk is supplied through the mammary ducts that are fed to the baby via the nipple. Near the nipple, the ducts expand to form ampullae, also known as the lactiferous sinuses. The milk gets stored here before being supplied through the ducts.

Mammary Glands in Females

This whole process is known as lactation which is controlled by the prolactin hormone. The discharge of milk is controlled by the pituitary gland stimulated by the oxytocin hormone.

Ques. What is the role of the pituitary gland during the menstrual cycle?

Ans. Gonadotropin-releasing hormone (GnRH) is emitted by the hypothalamus of the brain, which stimulates the influx of follicle-stimulating hormone (FSH) and luteinizing hormone (LH). FSH stirs the ovarian follicles to deliver oestrogen during the proliferative stage. LH stimulates the corpus luteum of the ovary to emit progesterone. The menstrual stage is brought about by the decrease of progesterone and oestrogens. The proliferative stage is the excessive release of oestrogens. 

LH causes ovulation. LH likewise causes a change of the void Graafian follicle into the corpus luteum by luteinization inside the ovary. LH likewise animates the corpus luteum to discharge progesterone chemical to help in implantation, placentation, and upkeep of pregnancy. A secretory stage is brought about by the increased release of progesterone.

Learn More About:

Also check: