NEET Biology Human Reproduction MCQs Set 26

Answer: (b) R. D. Graaf

Explanation:
1. Regnier de Graaf described the mammalian ovarian follicle.

Teacher's Note:
1. Von Baer discovered the mammalian egg.
2. Leeuwenhoek discovered sperm.

Answer: (b) Endocrine

Explanation:
1. It secretes hormones (progesterone, estrogen), so it is a temporary endocrine gland.

Teacher's Note:
1. Formed after ovulation.
2. LH maintains it.

Answer: (d) Secretory phase

Explanation:
1. After ovulation the corpus luteum forms and the endometrium becomes secretory.

Teacher's Note:
1. Follicular phase = proliferative phase.
2. Luteal phase lasts about 14 days.

Answer: (c) Menopause

Explanation:
1. Permanent end of menstrual cycles is menopause.

Teacher's Note:
1. Menarche is the first period.
2. Occurs around 50 years.

Answer: (a) LH

Explanation:
1. The LH surge causes ovulation and converts the ruptured follicle into the corpus luteum.

Teacher's Note:
1. LH is luteinizing hormone.
2. LTH (prolactin) helps milk production.

Answer: (a) Ovulation

Explanation:
1. Release of the secondary oocyte from the Graafian follicle is ovulation.

Teacher's Note:
1. Occurs about the 14th day.
2. Triggered by the LH surge.

Answer: (b) Inhibits further ovulation

Explanation:
1. High progesterone and estrogen levels suppress FSH and LH, so ovulation stops during pregnancy.

Teacher's Note:
1. Combined oral pills act likewise.
2. Menstrual cycles stop in pregnancy.

Answer: (b) The menstrual cycle is present in all primates

Explanation:
1. Menstruation occurs only in primates (humans, apes, monkeys).
2. Most other mammals show an estrous cycle.

Teacher's Note:
1. Not all mammals have estrous cycles (primates do not).
2. Most mammals are viviparous.

Answer: (d) Ovary, for secretion of progesterone

Explanation:
1. The corpus luteum is a temporary endocrine structure in the ovary that secretes progesterone.

Teacher's Note:
1. Corpus callosum connects the cerebral hemispheres.
2. Corpus luteum has a yellow pigment.

Answer: (d) Estrogen

Explanation:
1. Estrogen from growing follicles causes the repair and growth of the endometrium.

Teacher's Note:
1. Progesterone makes the endometrium secretory.
2. Oxytocin causes uterine contraction.

Answer: (b) Progesterone

Explanation:
1. Progesterone maintains the endometrium and suppresses uterine contraction in pregnancy.

Teacher's Note:
1. Called the hormone of pregnancy.
2. hCG maintains the corpus luteum early on.

Answer: (d) hCG

Explanation:
1. hCG is secreted by the placenta and passes into urine; pregnancy tests detect it.

Teacher's Note:
1. hCG appears about a week after implantation.
2. It keeps the corpus luteum active.

Answer: (d) Formation of the fertilization membrane

Explanation:
1. After the first sperm enters, the cortical reaction forms the fertilization membrane.
2. This blocks further sperm.

Teacher's Note:
1. Cortical granules release enzymes.
2. In mammals the zona reaction acts as the block.

Answer: (d) Both 1 and 2

Explanation:
1. Eggs with hard shells and development inside the female need internal fertilization.
2. Those developing in water use external fertilization.

Teacher's Note:
1. Aquatic animals mostly have external fertilization.
2. Terrestrial animals have internal fertilization.

Answer: (c) In the perivitelline space

Explanation:
1. Cortical granules discharge into the perivitelline space and form the fertilization membrane.

Teacher's Note:
1. It makes the zona impenetrable to more sperm.
2. It prevents polyspermy.

Answer: (d) All of the above

Explanation:
1. Cleavage is also called segmentation or cellulation.

Teacher's Note:
1. Cleavage divides the zygote into smaller blastomeres.
2. Total size does not increase.

Answer: (a) Fallopian tube

Explanation:
1. Mitotic division of the zygote begins while it is in the fallopian tube.

Teacher's Note:
1. The morula reaches the uterus after ~4 days.
2. Implantation occurs about day 7.

Answer: (b) Superficial

Explanation:
1. The yolk in the centre allows only the peripheral cytoplasm to divide: superficial cleavage.

Teacher's Note:
1. Seen in insects.
2. Telolecithal eggs of birds show discoidal cleavage.

Answer: (d) Differentiation of blastomeres

Explanation:
1. Cleavage is rapid mitosis with short interphase, making smaller cells.
2. Differentiation occurs later.

Teacher's Note:
1. No growth between divisions.
2. Differentiation starts at gastrulation.

Answer: (d) Chick

Explanation:
1. Yolk-rich eggs like those of birds undergo partial (meroblastic) cleavage.

Teacher's Note:
1. Amphioxus: holoblastic equal.
2. Frog: holoblastic unequal.

Answer: (c) Starts when the egg is in the fallopian tube

Explanation:
1. The zygote starts to divide in the fallopian tube.
2. Human cleavage is holoblastic.

Teacher's Note:
1. Morula is reached on the 3rd-4th day.
2. Human eggs lack much yolk.

Answer: (b) Unequal holoblastic

Explanation:
1. Moderate yolk makes the lower cells larger, so cleavage is unequal holoblastic (frog).

Teacher's Note:
1. Heavily yolked eggs show meroblastic cleavage.
2. Yolk slows division.

Answer: (b) Size of cells decreases

Explanation:
1. Cleavage divides the zygote without growth, so blastomeres get smaller while the overall embryo size stays the same.

Teacher's Note:
1. Cell number increases, size per cell decreases.
2. Nucleocytoplasmic ratio rises.

Answer: (c) Morula

Explanation:
1. The morula is a solid mulberry-like ball of blastomeres.

Teacher's Note:
1. The blastula has a cavity.
2. Gastrula has germ layers.

Answer: (d) All of these

Explanation:
1. Gastrulation forms the three primary germ layers.

Teacher's Note:
1. Ectoderm, mesoderm, endoderm.
2. Each gives specific organs.