Short & Long Question Answers with Solution: Human Reproduction | Biology for SSS 3 PDF Download

Short Answer Type Questions

Q1: Write the main functions each of testis and ovary?
Ans: The testes, also known as the testicles, are a pair of oval-shaped organs enclosed in a pouch called the scrotum. They play a crucial role in sperm production and the secretion of the male hormone testosterone.
On the other hand, the ovary is a ductless reproductive gland that primarily produces the female sex hormone estrogen. It is also responsible for the production and storage of egg cells, known as ova.

Q2: A sperm has just fertilised a human egg in the fallopian tube. Write down the events that the fertilised eggs will go through till the implantation of the blastocyst in the uterus.
Ans: 

• Cleavage: When the zygote travels through the isthmus of the oviduct, mitotic division begins, known as cleavage, as it approaches the uterus. This process results in the formation of 2, 4, 8, or 16 daughter cells called blastomeres.
• Blastocyst: Following fertilization, the morula undergoes further division, forming a large mass of cells called a blastocyst. The outer peripheral cells of the blastocyst enlarge and flatten, eventually giving rise to the trophoblast. Trophoblast cells release fluid into the interior, forming a cavity known as the blastocoel. This embryonic stage, characterized by the presence of the blastocoel, is referred to as a blastula.

Q3: What is meant by L.H. Surge? Write the role of L.H.
Ans: The menstrual cycle consists of three phases: the follicular phase, the ovulatory phase, and the luteal phase. The ovulatory phase is particularly significant in terms of the surge of luteinizing hormone (LH).
In the follicular phase, which marks the start of the menstrual cycle, a follicle begins to develop. The menstrual cycle commences with the menstrual period, which involves the shedding of the uterine lining. This shedding helps cleanse the uterine lining in preparation for ovulation, which occurs during the ovulatory phase.

Q4: Define Fertilization.
Ans: Fertilization is the biological process that involves the fusion of male and female gametes, leading to the formation of a zygote. In humans, this fertilization process occurs within the fallopian tube.

Q5:  ‘A fertilised egg is the blueprint of future development’. Explain the statement.
Ans: The father's genetic material is carried by the sperm, which includes 23 chromosomes, including either the X or Y sex chromosome. On the other hand, the mother's genetic material is carried by the egg, which includes the X sex chromosome. Therefore, when fertilization occurs and these male and female gametes fuse, it results in a unique genetic combination that brings about genetic diversity in the offspring. The zygote, or the fertilized egg, contains this genetic information, which guides the development of the embryo.

Q6: Explain significance of the condition in which the testes remain suspended in scrotum outside the abdomen.
Ans: Sperm production in humans is not possible at the body's normal temperature. The process of spermatogenesis and the health of the seminiferous tubules require a slightly lower temperature than the body's core temperature. The scrotum, which is located outside the abdominal cavity, provides this lower temperature necessary for sperm development and maintenance.

Q7: Define Parturition.
Ans: Parturition, also known as childbirth, is the process of delivering a baby from the uterus through the vagina to the outside world.
It typically occurs in three stages:

• Dilation: During this stage, the cervix begins to dilate (widen) and efface (thin out) to allow the baby to pass through the birth canal.
• Expulsion: In this stage, the baby is pushed through the birth canal and is born.
• Placental: After the baby is born, the placenta is expelled from the uterus.

Q8: State the male accessory glands and their function.
Ans: The male reproductive system consists of accessory glands such as the prostate gland, paired seminal vesicles, and paired bulbourethral glands. These glands release seminal plasma, which contains substances like calcium, fructose, and enzymes. Seminal fluid provides essential nutrients and enzymes to support sperm function. Moreover, the bulbourethral glands produce fluids that help lubricate the penis during sexual arousal and intercourse. Together, these accessory glands contribute to the composition of semen, which is expelled during ejaculation and plays a critical role in fertilization.

Q9: Enlist any two functions of a female placenta.
Ans: The placenta, which serves as both the structural and functional interface between the developing embryo and the mother, plays a crucial role in providing nutrients and oxygen to the embryo while removing carbon dioxide and other waste products generated by the embryo. Additionally, the placenta functions as an endocrine organ, producing various hormones.

Q10: Mention the changes taking place during the transition of a primary follicle to Graafian follicle in the oogonia.
Ans: Oogonia, which are the precursor cells for gametes, are generated within each fetal ovary. No additional oogonia are produced after birth. These oogonia undergo the prophase-I stage of meiotic division, initiating cell division towards becoming primary oocytes. These primary oocytes are surrounded by a layer of granulosa cells, forming the primary follicle. The primary follicles undergo degeneration from birth to puberty. More layers of granulosa cells and a new theca, composed of an outer theca externa and an inner theca interna that produces estrogen, encircle the primary follicles, transforming them into secondary follicles. The secondary follicle further develops into a tertiary follicle characterized by the presence of an antrum, a fluid-filled cavity. During this stage, the primary oocyte within the tertiary follicle increases in size as it completes the first meiotic division. Finally, the tertiary follicle matures into a Graafian follicle.

Q11: Where are the Leydig cells situated? What do they release?
Ans: The Leydig cells, also known as interstitial cells, are located in the spaces between the seminiferous tubules. These Leydig cells produce the male sex hormone called 'testosterone.' Testosterone plays a crucial role in promoting the development of accessory glands and controlling the development of secondary sexual characteristics in males.

Q12: Explain significance of the condition in which the testes remain suspended in scrotum outside the abdomen.
Ans: Human sperm cells cannot develop at body temperature, as spermatogenesis and the maintenance of the seminiferous tubules require a slightly lower temperature than that of the body. This lower temperature is provided by the scrotum, which is situated outside the abdominal cavity.

Q13: What are the different stages of the follicular phase of the menstrual cycle taking place in ovary and uterus?
Ans: During this phase, primary follicles in the ovary undergo transformation into fully mature Graafian follicles. Simultaneously, the endometrium of the uterus regenerates through proliferation. This phase is characterized by changes in the levels of ovarian and pituitary hormones, which induce changes in the uterus and ovaries. As this stage progresses, the secretion of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) gradually increases, leading to the secretion and follicular development of estrogen by the growing follicles. In the middle of the menstrual cycle, both LH and FSH reach their peak levels. This rapid secretion of LH at its maximum level during the mid-cycle triggers the rupture of the Graafian follicle and, consequently, ovulation.

Q14: What is colostrum? State its importance to a newborn baby.
Ans: The initial milk produced by mammary glands immediately after birth for a period of 2 to 3 days is referred to as colostrum. Colostrum is characterized by its high protein content and low fat content. It also contains the antibody IgA, which plays a crucial role in providing immunity to newborn infants.

Q15: What is meant by L.H. Surge? Write the role of L.H.
Ans: The menstrual cycle consists of three main phases: the follicular phase, ovulatory phase, and luteal phase. Among these phases, the ovulatory phase holds particular significance due to the surge in luteinizing hormone (LH). The menstrual cycle commences with the menstrual period, which involves the shedding of the uterine lining, effectively cleansing the uterus in preparation for ovulation, which occurs during the ovulatory phase.

Long Answer Type Questions

Q1: What is the menstrual cycle? Name the Hormones which control the menstrual cycle.
Ans: The menstrual cycle, a natural process occurring in all females after puberty, involves the release of a mature egg from an ovary. If the egg remains unfertilized, the uterine lining sheds, marking the start of a new cycle. Typically, a menstrual cycle spans 28 days, though it can range from 21 to 35 days in some individuals.
This entire process is regulated by the endocrine system, with key hormones such as FSH, LH, estrogen, and progesterone playing pivotal roles. FSH and LH are produced by gonadotropic cells, while the ovaries produce progesterone.

Q2: Where does oogenesis occur? Explain the stages of this process.
Ans: Oogenesis is the process of ovum formation and maturation that takes place in the ovaries of a female fetus during embryonic development.
It consists of three phases:

• Multiplication Phase: Oogonia, derived from primordial germ cells through meiosis, undergo repeated mitotic divisions, forming clusters. Within each cluster, only one oogonium enters the growth phase and becomes the primary oocyte.
• Growth Phase: After reaching puberty, the growth phase begins, resulting in a significant increase in the size of the primary oocyte.
• Maturation Phase: During the first meiotic division, two haploid (n) cells are produced. This division is unequal, yielding a larger daughter cell with most of the cytoplasm, known as the secondary oocyte, and a smaller one with less cytoplasm called the polar body. The secondary oocyte then undergoes a second meiotic division to form an ovum and a second polar body.

Q3:  ‘A fertilized egg is the blue print of future development’. Explain.
Ans: Sperm contains 23 chromosomes, including the male sex chromosome (X or Y), from the father, while the egg contains genetic information from the mother, including the female sex chromosome (X). When fertilization occurs, the fusion of these male and female gametes creates a new genetic combination, introducing genetic variation in the offspring. The zygote, or fertilized egg, carries this genetic information, which subsequently controls the development of the embryo.

Q4: What is Menopause??
Ans: Menopause is the natural cessation of a woman's menstrual cycle, fertility, and associated changes that typically occurs in older women, usually between the ages of 40 and 50, though this can vary. The primary reason for menopause is the gradual reduction in female sex hormone levels as women age, leading to the cessation of egg release from the ovaries. Consequently, women going through menopause no longer have menstrual periods and are unable to conceive.

Q5: What is menstruation? What are the roles of FSH, LH, oestrogen & progesterone in the menstrual cycle?
Ans: On the 28th day of the menstrual cycle, the endometrial lining in the female genital tract breaks down, resulting in bleeding, due to a lack of progesterone. This monthly blood flow is referred to as menstruation.
Throughout the menstrual cycle, various hormonal changes influence the ovary, including:

• Menstrual Phase: The endometrial lining of the uterus breaks down due to very low levels of hormones LH, FSH, estrogen, and progesterone.
• Follicular Phase: An increase in pituitary hormones FSH and LH leads to the release of estrogen, which controls the growth of follicles. Around the 14th day of the cycle, both FSH and LH reach their peak levels.
• Ovulatory Phase: The peak level of LH hormones, known as the LH surge, triggers the rupture of the mature Graafian follicle, resulting in the release of the ovum.
• Luteal Phase: LH and FSH hormone levels start to decline significantly. After ovulation, the ruptured follicle transforms into the corpus luteum, which produces high levels of progesterone.

Q6: Differentiate between spermatogenesis and oogenesis.
Ans:

Q7: What is the female reproductive system?
Ans: The female reproductive system comprises both internal and external organs that play a vital role in the process of reproduction.
Internal Reproductive Organs: Females have several internal reproductive organs, including the vagina, uterus (womb), cervix, fallopian tubes, and ovaries.
External Reproductive Organs: The external reproductive organs, collectively referred to as the vulva, encompass all the external parts of the female reproductive system.

Q8: Explain the menstrual cycle with a diagram.
Ans: The menstrual cycle can be divided into three phases: the menstrual phase, the proliferative phase, and the secretory phase.
(a) Menstrual Phase: This phase typically spans 3-5 days in human females. During this time, the lining of the uterus, known as the endometrium, is shed and expelled through the vagina in the form of a blood mixture.
(b) Proliferative or Follicular Phase: Occurring from the 6th to the 16th day of the cycle, this phase lasts for about 11 days. It involves the transformation of one ovarian follicle into a Graafian follicle and the restoration of the endometrial lining, including the repair of ruptured blood vessels. Estrogen levels rise during this phase, which concludes with ovulation.
(c) Secretory Phase: Extending from the 17th to the 28th day, this phase lasts for approximately 12 days. It involves the conversion of the Graafian follicle into the Corpus Luteum. The endometrium continues to grow and thicken. Progesterone levels increase during this phase, which concludes with the transformation of the Corpus Luteum into the Corpus Albicans.

Q9: What do the term parturition and lactation mean?
Ans: Parturition is the process in which strong contractions occur to deliver a fully developed fetus at the end of pregnancy. This process is initiated by signals from the mature fetus and placenta, leading to mild uterine contractions known as the fetal ejection reflex.
Oxytocin release from the maternal pituitary gland is also triggered.
The production of milk by the mammary glands in a female is referred to as "Lactation." It typically begins towards the end of pregnancy. During the early stages of lactation, the produced milk is called colostrum, which contains essential antibodies for the newborn.

Q10: What is Reproduction? Explain how humans reproduce their young ones?
Ans: Reproduction is a biological process that results in the production of offspring, which may or may not be identical to their parents. There are two primary modes of reproduction, which are categorized based on parental involvement.
These two modes of reproduction are:

• Asexual Reproduction: In this mode, only one parent is involved, and the offspring produced are genetically identical to the parent.
• Sexual Reproduction: This mode involves the formation and transfer of gametes, followed by fertilization, which leads to the formation of a zygote and subsequent embryogenesis. It is a more complex process.

Humans, as a species, reproduce through sexual reproduction.