Reproduction in Organisms Test - 1

• Menopause is a natural biological process that marks the end of a woman 's reproductive years.
• It occurs when a woman 's ovaries stop producing eggs and her body produces lower levels of estrogen and progesterone hormones.
• The average age for menopause is 50 years , but it can happen earlier or later, usually between the ages of 45 and 55 .
• Some factors that may influence the age of menopause include genetics, smoking, and certain health conditions.
• During menopause, a woman may experience various symptoms, such as hot flashes, night sweats, and mood changes.

Hence, the Correct Answer is B

NCERT Reference:  T opic “Menstrual cycle ”of chapter: Human Reproduction of NCERT.

The correct answer is b. A human female reaches menopause around the age of 50 years.

Corona Radiata

• The corona radiata is a layer of cells that surround the oocyte (immature egg cell) in the ovarian follicle.
• These cells provide nourishment and support to the developing oocyte.
• The corona radiata remains attached to the oocyte during ovulation and helps in the recognition and binding of sperm during fertilization.

Zona Pellucida

• The zona pellucida is a transparent, glycoprotein layer that surrounds the oocyte and is located just outside the cell membrane.
• It plays a crucial role in protecting the oocyte, regulating sperm binding and penetration, and preventing polyspermy (entry of multiple sperm cells).

Zona Radiata

• Zona radiata is not a correct term related to the ovum. It might be confused with the corona radiata or zona pellucida, but it is not a valid term in this context.

Chorion

• The chorion is an extraembryonic membrane that develops from the outer cells of the blastocyst after fertilization.
• It is involved in the formation of the placenta and plays a role in gas exchange, nutrient transport, and waste removal between the mother and the developing fetus.

In summary, the corona radiata is the correct answer because it is the membranous cover of the ovum at ovulation, providing support and nourishment to the developing oocyte.

As we know that spermatogenesis as the name suggests is the process of generation of sperms.

• Spermatogonia or the immature germ cells are present within the seminiferous tubules
• These cells divide by mitosis and some of them enter Meiosis I to become primary spermatocytes and then they complete Meiosis I to become secondary spermatocytes.
• Secondary spermatocytes now undergo Meiosis II to become spermatids which will differentiate into spermatozoa or sperms and will be released into the lumen of tubules.
• In these tubules, two types of cells present one is Sertolis cells which will provide nutrition to the growing sperms and the Leydig cells which secretes Testosterone which helps in maintaining the reproductive tract.
• Testosterone is a male hormone that is responsible for the male reproductive system 's maintenance.

Therefore, from the above explanation we can say that spermatogenesis is promoted by Testosterone .

Hence, the Correct Answer is C

Spermatogenesis ​:

NCERT Reference: Topic “Gametogenesis ”of chapter: Human Reproduction of NCERT.

Menstrual Cycle Phases:

• The menstrual cycle is divided into several phases, including the follicular phase, ovulation, and the luteal phase.

(i) Follicular Phase:

• During the follicular phase, the level of estrogen increases, which stimulates the growth and development of follicles containing the eggs (ova).
• Estrogen also helps in thickening the endometrium (uterine lining) to prepare it for the potential implantation of a fertilized egg.

(ii) Ovulation:

• Ovulation is triggered by a surge in luteinizing hormone (LH), not by high levels of estrogen, so statement a is incorrect.
• During ovulation, a mature egg is released from the dominant follicle and enters the fallopian tube.

(iii) Luteal phase (post ovulatory phase):

• After ovulation, the remnants of the dominant follicle transform into the corpus luteum, which secretes progesterone.
• Progesterone is responsible for maintaining the endometrial lining and preparing it for the possible implantation of a fertilized egg.

Hence, statement b is correct, as progesterone levels are high during the post ovulatory phase of the menstrual cycle.

Sperms and oogonial cells:

• Statement c is incorrect because sperms released from seminiferous tubules are not fully motile, but they gain motility as they travel through the epididymis, where they mature and become capable of fertilizing an egg.
• Statement d is also incorrect because oogonial cells do not proliferate and give rise to functional ova during regular cycles. Instead, oogonial cells differentiate into primary oocytes before birth, and these primary oocytes are arrested in meiosis until puberty. From puberty onwards, a few primary oocytes resume meiosis and develop into functional ova during each menstrual cycle.

So, the correct answer is "Progesterone level is high during the post-ovulatory phase of the menstrual cycle."

Hence, the Correct Answer is B

NCERT Reference: Topic “Menstrual Cycle ”of chapter : Human Reproduction of NCERT.

• Zygote is  diploid (46 chromosomes i.e. 23 pairs of chromosomes) and  formed by fusion of male and female gametes.
• Spermatogonia are the cells on the inside wall of seminiferous tubules and consist of 46 chromosomes.
• The secondary oocyte is a haploid cell that develops from the primary oocyte during puberty. It is a haploid cell with23 chromosomes .
• Oogonia are also diploid and are formed in the foetal ovary.​

Hence, the Correct Answer is C

NCERT Reference: T opic Gametogenesis ”of chapter - Human Reproduction of NCERT

Ovulation is a critical event in the menstrual cycle, during which the mature ovum is released from the Graafian follicle. This process is regulated by hormones, including Estrogen, Progesterone, Luteinizing Hormone (LH), and Follicle-Stimulating Hormone (FSH). The release of the ovum is primarily driven by a high concentration of Estrogen.

• High concentration of Estrogen: Estrogen is produced by the growing follicles in the ovary. As the follicles mature, the levels of Estrogen increase. When the Estrogen level reaches a threshold, it triggers a surge in the Luteinizing Hormone (LH). This LH surge is responsible for initiating the process of ovulation. Therefore,a high concentration of Estrogen is necessary for the release of the ovum from the Graafian follicle.

• High concentration of Progesterone:  Progesterone is not responsible for triggering ovulation. Instead, it is involved in preparing the endometrium for implantation of the fertilized ovum and maintaining pregnancy. Progesterone levels rise after ovulation has occurred under the influence of LH.
• Low concentration of LH: A low concentration of LH does not cause ovulation. In fact, it is the surge in LH levels, triggered by high Estrogen levels, that stimulates the release of the ovum from the Graafian follicle.
• Low concentration of FSH : FSH plays a role in the growth and maturation of ovarian follicles. However, a low concentration of FSH is not directly responsible for the release of the ovum. It is the high concentration of Estrogen, produced by the maturing follicles, that ultimately triggers ovulation. Ovulation occurs when the level of hormones is as follows:

Hence, the Correct Answer is D

NCERT Reference:  Topic “Menstrual cycle ”of chapter: Human Reproduction of NCERT.

• Primary and secondary spermatocytes are formed through the process of spermatocytogenesis. Primary spermatocytes are diploid (2N) cells. After meiosis I, two secondary spermatocytes are formed. Secondary spermatocytes are haploid (N) cells that contain half the number of chromosomes.
• During meiotic cell-cycle progression, unequal divisions take place, resulting in a large oocyte and two diminutive polar bodies. Both these polar bodies are haploid in nature.
• A secondary oocyte only undergoes the second meiotic cell division to form a haploid ovum if it is fertilised by a sperm. The one egg cell that results from meiosis contains most of the cytoplasm, nutrients, and organelles. It is a haploid in nature.

Hence, the Correct Answer is B

NCERT Reference:  Topic “Gametogenesis ”and “Fertilisation and implantation ”of chapter: Human Reproduction of NCERT.

The presence of estradiol and progesterone in the luteal phase results in negative feedback on both FSH and  LH secretion. Because of this negative feedback, the levels of FSH and LH are relatively low in the luteal phase . This inhibits  FSH release  and thus restricts follicular development during the luteal phase.

Hence, the Correct Answer is D

NCERT Reference: Topic “Menstrual cycle ”of chapter: Human Reproduction of NCERT

Spermiogenesis

• In spermiogenesis, immature sperm cells called spermatids undergo a series of morphological and functional changes to become mature spermatozoa.
• Spermatids are formed from the process of meiosis during spermatogenesis.
• The process involves the development of an acrosome, elongation and condensation of the nucleus, formation of the tail, and other changes required for a sperm cell to become motile and capable of fertilizing an egg.

Spermiation

• Spermiation refers to the release of mature spermatozoa from Sertoli cells into the cavity of the seminiferous tubules.
• Sertoli cells are somatic cells that support and nourish the developing sperm cells throughout spermatogenesis.
• During spermiation, spermatozoa are detached from the Sertoli cells and move into the lumen of the seminiferous tubules, from where they will eventually be transported to the epididymis for storage and further maturation.

In summary, spermiogenesis involves the maturation of spermatids into spermatozoa, while spermiation involves the release of mature spermatozoa from Sertoli cells into the cavity of the seminiferous tubules.

Hence, the Correct Answer is D

NCERT Reference: T opic “Gametogenesis ”of chapter: Human Reproduction of NCERT

• LH is a Luteinizing hormone produced by the gonadotropic cells in the anterior pituitary gland.
• It plays an important role in puberty, menstruation, and fertility.
• It triggers ovulation and development of the corpus luteum.
• In male, LH triggers the secretion of androgen called testosterone from the Leydig cells.
• FSH is follicle-stimulating hormone produced by gonadotropic cells in the anterior pituitary gland.
• It helps in regulation of development, growth, pubertal maturation and reproductive processes of the body.
• It stimulates the Sertoli cells of the testicles and helps in spermatogenesis, production of sperm.
• During the follicular phase, the LH and FSH increase gradually.
• They stimulate follicular development and estrogen secretion by follicular cells.

Thus, the correct answer is 'LH and FSH decrease gradually during the follicular phase.'

Hence, the Correct Answer is B

NCERT Reference: T opic “Menstrual cycle ”of chapter: Human Reproduction of NCERT