Which of the following parameters are correct regarding human male ejaculate and fertility?
(I) During a single coitus, a human male ejaculates about 200 to 300 million sperms. (II) For normal fertility, at least 40% of sperms must have a normal shape and size. (III) For normal fertility, at least 40% of sperms must show vigorous motility. (IV) Normal fertility requires at least 60% of sperms to have a normal shape and size.
Explanation: Statements (I), (III), and (IV) are correct. According to NCERT, at least 60% of sperms should have a normal shape and size, and at least 40% should show vigorous motility. Therefore, statement (II) is incorrect.
Question 72 of 100
📘 CLASS XII
Concerning the maturation, motility, and maintenance of male sperms:
(I) Secretions of the epididymis, vas deferens, seminal vesicle, and prostate are essential for sperm maturation and motility. (II) Semen consists of seminal plasma combined with spermatozoa. (III) The functions of male accessory ducts and glands are maintained by pituitary gonadotropins directly. (IV) Androgens are the primary hormones maintaining the male sex accessory ducts and glands.
Explanation: Statements (I), (II), and (IV) are correct. Statement (III) is incorrect because the male accessory ducts and glands are maintained primarily by androgens, not directly by pituitary gonadotropins.
Question 73 of 100
📘 CLASS XII
Read the statements below regarding the onset and progression of oogenesis:
(I) Oogenesis is initiated during the embryonic development stage of the female. (II) A couple of million oogonia are formed within each fetal ovary during gestation. (III) No more oogonia are formed and added after birth. (IV) Oogonia enter prophase-I of meiotic division and complete it immediately before birth.
Explanation: Statements (I), (II), and (III) are correct. Statement (IV) is incorrect because primary oocytes become arrested in prophase-I until puberty.
Question 74 of 100
📘 CLASS XII
Trace the progression of primary follicles from birth to puberty:
(I) Each primary oocyte gets surrounded by a layer of granulosa cells to form a primary follicle. (II) A large number of primary follicles degenerate during the phase from birth to puberty. (III) At puberty, only about 60,000 to 80,000 primary follicles are left in the entire female body. (IV) Primary follicles get surrounded by more granulosa cells and a new theca to form secondary follicles.
Explanation: Statements (I), (II), and (IV) are correct. Statement (III) is incorrect because about 60,000 to 80,000 primary follicles remain in each ovary, not in the entire female body.
Question 75 of 100
📘 CLASS XII
Analyze the structural characteristics of a tertiary follicle and choose the correct statement combination:
(I) The tertiary follicle is characterized by a fluid-filled cavity called the antrum. (II) The theca layer is organized into an inner theca interna and an outer theca externa. (III) The primary oocyte within the tertiary follicle completes its first meiotic division. (IV) The first meiotic division is an equal division producing two haploid cells of equal size.
Explanation: Statements (I), (II), and (III) are correct. Statement (IV) is incorrect because the first meiotic division is an unequal division, producing a large secondary oocyte and a small first polar body.
Question 76 of 100
📘 CLASS XII
Read the statements below regarding the hormonal control of the menstrual cycle:
(I) Secretion of LH and FSH increases gradually during the follicular phase. (II) Estrogen secreted by the growing follicles stimulates the proliferation and regeneration of the endometrium. (III) A sudden rise in LH levels in the middle of the cycle causes the corpus luteum to form immediately before ovulation. (IV) Progesterone is secreted in high amounts by the intact Graafian follicle prior to its rupture.
Explanation: Statements (I) and (II) are correct because LH and FSH gradually increase during the follicular phase, stimulating follicular growth and estrogen secretion, which regenerates the endometrium. Statement (III) is incorrect because the LH surge induces ovulation; the corpus luteum forms only after rupture of the Graafian follicle. Statement (IV) is incorrect because high levels of progesterone are secreted by the corpus luteum, not by the intact Graafian follicle.
Question 77 of 100
📘 CLASS XII
Which of the following statements regarding the human zygote and sex determination are accurate?
(I) Sex of the baby is determined at the zygote stage itself. (II) All haploid gametes (ova) produced by human females contain only the X sex chromosome. (III) Males produce two types of gametes (sperms), where 50% carry X and 50% carry Y chromosomes. (IV) The sex of the baby is determined scientifically by the genetic contribution of the mother.
Explanation: Statements (I), (II), and (III) are correct. Statement (IV) is incorrect because the sex of the baby is determined by the father, whose sperms carry either an X or a Y chromosome.
Question 78 of 100
📘 CLASS XII
Examine the statements concerning the mitotic divisions (cleavage) of the human zygote:
(I) Cleavage begins as the zygote moves through the isthmus of the oviduct toward the uterus. (II) The cleavage divisions are typical meiotic divisions that reduce the chromosome number. (III) The daughter cells formed during these divisions are called blastomeres. (IV) An embryo with 8 to 16 blastomeres is specifically called a blastocyst.
Explanation: Statements (I) and (III) are correct. Statement (II) is incorrect because cleavage consists of rapid mitotic divisions. Statement (IV) is incorrect because an embryo with 8 to 16 blastomeres is called a morula, which later develops into a blastocyst.
Question 79 of 100
📘 CLASS XII
Regarding the structure and implantation of the blastocyst, choose the correct statements:
(I) Blastomeres in the blastocyst are arranged into an outer layer called the trophoblast. (II) The inner group of cells attached to the trophoblast is called the inner cell mass. (III) The inner cell mass attaches directly to the endometrium of the uterus. (IV) After implantation, the trophoblast layer gets differentiated as the embryo.
Explanation: Statements (I) and (II) are correct. Statement (III) is incorrect because the trophoblast attaches to the endometrium. Statement (IV) is incorrect because the inner cell mass develops into the embryo.
Question 80 of 100
📘 CLASS XII
Analyze the statements regarding the functional features of the human placenta:
(I) The placenta facilitates the supply of oxygen and nutrients to the developing embryo. (II) It helps in the removal of carbon dioxide and excretory/waste materials produced by the embryo. (III) The placenta acts as an endocrine tissue and produces hormones like hCG, hPL, estrogens, and progestogens. (IV) The placenta is connected to the embryo directly through the fallopian tube.
Explanation: Statements (I), (II), and (III) are correct. Statement (IV) is incorrect because the placenta is connected to the embryo through the umbilical cord, not the fallopian tube.
