Human ReproductionNEET Zoology · Class 12 · NCERT Chapter 1

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Tubectomy involves the removal or ligation of a small part of the fallopian tube to prevent fertilization. This method is a form of female sterilization, as described in NCERT XII Human Reproduction, so option (a) is correct.

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LNG-20 is a hormone-releasing Intra Uterine Device (IUD) that releases levonorgestrel. NCERT XII chapter Human Reproduction describes LNG-20 as an IUD that releases hormones to prevent pregnancy, so option (b) is correct.

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In vitro fertilization (IVF) involves the transfer of a zygote or early embryo into the uterus, not the fallopian tube. According to NCERT XII Human Reproduction, the correct option is (b).

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Any extra uterine pregnancy is ectopic pregnancy. Implantation can occur in the wall of abdominal cavity, ovaries but 90- 95% of ectopic pregnancies are tubal pregnancy where implantation occurs in fallopian tube.

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In 28 days reproductive cycle, ovulation occurs on 14th day due to LH surge. In the mid cycle, the level of FSH and estrogen are also high. The female gamete is released from the ovary in secondary oocyte stage after completing meiosis I.

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GIFT - Gamete intra fallopian transfer

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In human females, meiosis II is completed after the entry of sperm into the cytoplasm of secondary oocyte at the time of fertilisation leading to the formation of ovum and IInd polar body.

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Zona pellucida is non-cellular membrane made up of glycoproteins. It is secreted by secondary oocyte in Graafian follicle.

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Fertilization is practically only feasible if the ovum and sperms are transported simultaneously into the ampulla isthmus region of fallopian tube.

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LH and FSH both increase during follicular phase.

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Vasectomy causes sterilization by preventing transfer of sperms. www.vedantu.com 60

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Capacitation is increase in fertilising capacity of sperms which occurs in female reproductive tract.

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Inbreeding results in increase in the homozygosity. Therefore, mating of the related individuals of same breed will increase homozygosity.

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Total number of teeth in human child = 20. Premolars are absent in primary dentition.

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In male frog the sperms will move from Testes → Vasa efferentia → Kidney → Bidder’s canal → Urinogenital duct → Cloaca.

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Infertility cases due to inability of the male partner to inseminate the female or due to very low sperm count in the ejaculates, could be corrected by artificial insemination (AI).

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Cu 2+ interfere in the sperm movement, hence suppress the sperm motility and fertilising capacity of sperms.

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SAHELI is an oral contraceptive that blocks estrogen receptors in the uterus, preventing the implantation of the egg. NCERT XII chapter Human Reproduction describes SAHELI as a non-steroidal, anti-fertility drug, so option (c) is correct.

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- Proliferative Phase: ii. Follicular Phase
- Secretory Phase: iii. Luteal Phase
- Menstruation: i. Breakdown of endometrial lining

According to NCERT XII Human Reproduction, these phases and their corresponding events are correctly matched in option (d).

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Factual- NCERT

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Factual NCERT

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Factual- NCERT

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Mutations are random and directionless.

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Ref. XI NCERT Chapter- 15, Page No. 252

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Ref. XII NCERT Chapter- 05, Page No. 83

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Zygote Intrafallopian Transfer (ZIFT) and Gamete Intrafallopian Transfer (GIFT) are techniques where embryos or gametes are transferred to the fallopian tubes to assist conception. NCERT XII chapter Human Reproduction describes these techniques, so option (b) is correct.

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High concentrations of estrogen trigger the release of luteinizing hormone (LH), which in turn causes ovulation. NCERT XII chapter Human Reproduction explains that a surge in LH levels, induced by high estrogen, leads to the rupture of the Graafian follicle and release of the ovum, so option (a) is correct.

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Meiotic division of the secondary oocyte is completed at the time of fusion of a sperm with an ovum, forming the second polar body. NCERT XII chapter Human Reproduction states that the secondary oocyte completes its second meiotic division only after fertilization, so option (d) is correct.

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- Placenta produces Human Chorionic Gonadotropin (hCG).
- Zona pellucida is a layer of the ovum.
- Bulbo-urethral glands provide lubrication of the penis.
- Leydig cells produce androgens.

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LNG 20 is a hormone-releasing IUD that releases levonorgestrel, a progestin hormone, to prevent pregnancy. NCERT XII chapter Human Reproduction lists LNG 20 as an example of a hormone-releasing IUD, so option (b) is correct.

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- Vaults: (i) Entry of sperm through cervix is blocked.
- IUDs: (iii) Phagocytosis of sperms within the uterus.
- Vasectomy: (ii) Removal of vas deferens.
- Tubectomy: (iv) Removal of fallopian tube.

Thus, the correct option is (b).

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Receptors for sperm binding are present on the zona pellucida, which is a glycoprotein layer surrounding the mammalian egg. NCERT XII chapter Human Reproduction describes the zona pellucida as the site of sperm binding and subsequent acrosome reaction, so option (d) is correct.

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Prolactin is not a key component in the initiation of parturition. The increase in the estrogen to progesterone ratio, synthesis of prostaglandins, and release of oxytocin are the primary factors that initiate labor, as described in NCERT XII Human Reproduction. Therefore, option (d) is correct.

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Relaxin is secreted by the corpus luteum during the later phase of pregnancy to facilitate childbirth by relaxing the pelvic ligaments. NCERT XII chapter Human Reproduction describes the role of the corpus luteum in hormone secretion, so option (b) is correct.

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In MOET, the cow is administered hormones for superovulation, typically yielding more than 6-8 eggs. The number of eggs can be much higher, often around 20-30. Therefore, option (b) is not a correct step in MOET, as it underestimates the number of eggs produced.

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Option (4) is the correct answer. • In both, spermatogenesis and oogenesis haploid gametes are formed. So (a) is true for both. • The spermatids are transformed into spermatozoa (sperms) by the process called spermiogenesis. Hence, (b) is true for spermatogenesis only. • Spermatogenesis and oogenesis both are controlled by LH and FSH secreted by the anterior pituitary. Hence (d) is true for both. • Spermatogenesis is a continuous process that begins at puberty. So (e) is true for spermatogenesis. Oogenesis on the other hand begins during embryonic development of the female.

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Option (3) is the correct answer because the intrauterine device (IUD) presently available as the non- medicated IUDs, is Lippe’s loop. Option (4) is incorrect as copper releasing IUDs are CuT, Cu7 and multiload 375. Option (1) and (2) are incorrect as diaphragms, cervical caps and vaults are included in barrier method of contraception.

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isMeiosis involves two sequential cycles of nuclear and cell division called meios -I and meiosis-II but only single cycle of DNA replication. The stage between two meiotic divisions is called interkinesis and is generally short lived and involves no DNA replication.

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Option (3) is the correct answer because Sta tement II is incorrect as the transformation of spermatids into spermatozoa (sperms) are called spermiogenesis. After this, sperm head becomes embedded in the Sertoli cells and are finally released from the seminiferous tubules by the process called spermiation. Hence, Statement I is a correct statement. Spermatogenesis is the process of formation of sperms from spermatogonia.

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Option (2) is the correct answer as oogenesis is initiated during the embryonic development stage when a couple of million gamete mother cells (oogonia) are formed within each foetal ovary. No more oogonia are formed and added after birth in a human female. At puberty only 60,000 to 80,000 prim ary follicles are left in each ovary, rest degenerate during the phase from birth to puberty.

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Option (2) is the correct answer because • Diaphragms are barrier methods of contraception. They cover the cervix and block the entry of sperms. • Contraceptive pills are preparations containing either progestogens alone or combination of progestogen and oestrogen. They inhibit ovulation and implantation as well as alter the quality of cervical mucus to prevent entry of sperms. • Intra uterine devices increase the phagocytosis of sperms within the uterus. • Lactational amenorrhoea is a natural method of contraception and it is based on the fact that the ovulation and therefore menstrual cycle do not occur during the period of intense lactation following parturition. - 69 - NEET (UG)-2022 (Code- Q1)

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Klinefelter’s Syndrome is characterized by the presence of an extra X chromosome (XXY), leading to overall masculine development with some feminine traits and sterility. The affected individuals are typically tall, not short, and do not show significant retardation in physical, psychomotor, or mental development, so option (d) is correct.

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Statement I is true as the vas deferens does receive a duct from the seminal vesicle and opens into the urethra as the ejaculatory duct. Statement II is also true as the cervical canal, along with the vagina, forms the birth canal. Both statements are accurate according to NCERT XII Human Reproduction, so option (b) is correct.

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Both statements are true. The endometrium is essential for blastocyst implantation, and in the absence of fertilization, the corpus luteum degenerates, leading to endometrial disintegration. However, the reason does not explain the necessity of the endometrium for implantation, so option (c) is correct.

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Statement A is correct as non-primate mammals exhibit oestrus cycles. Statement B is incorrect; the first menstrual cycle is called menarche, not menopause. Statement C is correct; lack of menstruation can indicate pregnancy. Statement D is correct; cyclic menstruation occurs between menarche and menopause. Therefore, option (a) is correct.

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A broad palm with a single transverse crease is a characteristic feature of Down’s syndrome, which is caused by trisomy of chromosome 21. NCERT XII chapter Human Reproduction describes this as one of the physical traits associated with Down’s syndrome, so option (b) is correct.

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The correct answer is option no. (3) because the presence or absence of hymen is not a reliable indicator of virginity because hymen can also be broken by a sudden jolt, insertion of a vaginal tampon, active participation in some sports and in some women the hymen persists even after coitus.

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The correct answer is option (4) as FSH is a gonadotropin affects ovarian follicles in females and causes their growth but in males LH affects Leydig cells leading to secretion of androgens. Growing ovarian follicles secrete estrogen in females while interstitial cells secrete androgen in male human being. Hence, Assertion is false and Reason is true.

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The correct answer is option (1) as uterine fundus is the upper, dome-shaped part of the uterus, above the opening of fallopian tubes. • Option (2) is incorrect as isthmus is the last and narrow part of the oviduct that links to the uterus. • Option (3) is incorrect as infundibulum is the part of oviduct which is closer to the ovary. • Option (4) is incorrect as ampulla is the wider part of the oviduct.

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The correct answer is option no. (1) as (A) is FSH which is a pituitary hormone. (B) is Leydig cells which are found in the interstitial space outside of the seminiferous tubules. (C) is Sertoli cells are found inside the seminiferous tubules. (D) is Spermiogenesis which is a process that helps in transformation of spermatids into spermatozoa.

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In male frogs, copulatory pad is present on the first digit of the forelimbs which are absent in female frogs.

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The sperm head contains elongated nucleus which possesses the genetic material.

The middle piece possesses numerous mitochondria, which produce energy for movement.

Acrosome is a cap-like structure filled with enzymes that help in fertilization of ovum.

The tail of sperm facilitates sperm motility essential for fertilisation.

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In a human female’s pregnancy.
• By the end of 12 weeks (1st trimester), most of major organ systems are formed (not by end of 8 weeks).

• After one month of pregnancy, the embryo’s heart is formed.

• By the end of second month of pregnancy, the foetus develops limbs and digits.

• The first movements of foetus and appearance of hair on head are usually observed during the fifth month.

Solution

Statements A and B are true while statements C and D are false.

The first polar body is associated with the formation of the secondary oocyte LH surge leads to ovulation.
Decreased levels of progesterone during late luteal phase leads to degeneration of the endometrium and onset of menstrual bleeding.

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Sol. The first menstruation begins at puberty and is called menarche.

• Ovulation is the process that deals with the release of secondary oocyte from the mature Graafian follicle.

• In human beings, menstrual cycles ceases around 50 years of age; that is termed as menopause.

• Diapause is a state of dormancy or developmental arrest in an organism.

Solution

The sperm head contains elongated nucleus which possesses the genetic material.

The middle piece possesses numerous mitochondria, which produce energy for movement.

Acrosome is a cap-like structure filled with enzymes that help in fertilization of ovum.

The tail of sperm facilitates sperm motility essential for fertilisation.

Solution

Twins of different sexes (boy and girl) are always fraternal (dizygotic) twins, as monozygotic twins are always of the same sex. NCERT XII chapter Human Reproduction states that monozygotic twins result from a single fertilized egg, while fraternal twins result from two separate eggs fertilized by different sperm, so option (b) is correct.