Reproduction in Plants and Humans — Practice

Question 1

The male reproductive whorl of a flower, made of stamens, is the:
(a) androecium (b) gynoecium (c) corolla (d) calyx

Accepted Answer

(a) androecium.

The androecium is the whorl of stamens (anther + filament) — the male reproductive part. The gynoecium (carpels) is the female whorl; calyx and corolla are accessory whorls.

Question 2

The tough, highly resistant outer wall of a pollen grain is made of:
(a) sporopollenin (b) cellulose (c) chitin (d) lignin

Accepted Answer

(a) sporopollenin.

The exine of the pollen grain is made of sporopollenin, the most resistant known biological material, able to survive high temperature and strong acids. The inner intine is of cellulose and pectin.

Question 3

One microspore mother cell produces how many pollen grains?
(a) four (b) two (c) one (d) eight

Accepted Answer

(a) four.

Meiosis of one diploid microspore mother cell yields four haploid microspores (a tetrad), each of which becomes a pollen grain — so four pollen grains per mother cell.

Question 4

Of the four megaspores formed from a megaspore mother cell, the number that is normally functional is:
(a) one (b) two (c) three (d) all four

Accepted Answer

(a) one.

Meiosis gives four megaspores, but usually three degenerate and only one functional megaspore survives to form the embryo sac (monosporic development).

Question 5

A typical mature embryo sac is:
(a) 7-celled and 8-nucleate (b) 8-celled and 8-nucleate (c) 7-celled and 7-nucleate (d) 6-celled and 8-nucleate

Accepted Answer

(a) 7-celled and 8-nucleate.

The embryo sac has 8 nuclei but 7 cells because the central cell contains two polar nuclei: 1 egg + 2 synergids + 3 antipodals + 1 (binucleate) central cell.

Question 6

The egg apparatus at the micropylar end of the embryo sac consists of:
(a) one egg and two synergids (b) three antipodals (c) two polar nuclei (d) one egg only

Accepted Answer

(a) one egg and two synergids.

The egg apparatus comprises the egg cell flanked by two synergids (which bear the filiform apparatus guiding the pollen tube). The three antipodals lie at the opposite (chalazal) end.

Question 7

In double fertilisation, the primary endosperm nucleus formed by triple fusion is:
(a) triploid (3n) (b) diploid (2n) (c) haploid (n) (d) tetraploid (4n)

Accepted Answer

(a) triploid (3n).

Triple fusion unites one male gamete (n) with the two polar nuclei (n + n), giving a triploid (3n) primary endosperm nucleus. Syngamy gives the diploid (2n) zygote.

Question 8

After fertilisation, the ovary of a flower develops into the:
(a) fruit (b) seed (c) embryo (d) endosperm

Accepted Answer

(a) fruit.

The ovary wall becomes the pericarp of the fruit, while the ovule becomes the seed (integuments → seed coat, zygote → embryo, PEN → endosperm).

Question 9

Testosterone in the human male is secreted by the:
(a) Leydig (interstitial) cells (b) Sertoli cells (c) seminiferous tubule lumen (d) epididymis

Accepted Answer

(a) Leydig (interstitial) cells.

The Leydig cells between the seminiferous tubules secrete testosterone. Sertoli cells nourish the developing sperm; the tubules themselves are the site of spermatogenesis.

Question 10

The acrosome of a sperm, containing enzymes to penetrate the egg, is located in the:
(a) head (b) middle piece (c) tail (d) neck

Accepted Answer

(a) head.

The sperm head carries the nucleus capped by the acrosome (with hydrolytic enzymes). The middle piece packs mitochondria for energy; the tail (flagellum) provides motility.

Question 11

One primary spermatocyte and one primary oocyte respectively produce:
(a) 4 sperms and 1 ovum (b) 1 sperm and 4 ova (c) 4 sperms and 4 ova (d) 2 sperms and 2 ova

Accepted Answer

(a) 4 sperms and 1 ovum.

One primary spermatocyte yields four functional sperms; one primary oocyte yields only one functional ovum (plus polar bodies), because oogenesis divides the cytoplasm unequally.

Question 12

In human females, the primary oocytes are arrested at which stage until each menstrual cycle?
(a) prophase I (b) metaphase II (c) anaphase I (d) telophase II

Accepted Answer

(a) prophase I.

Primary oocytes enter and arrest at prophase I of meiosis before birth. Each cycle one resumes to give a secondary oocyte; meiosis II completes only if fertilisation occurs.

Question 13

Ovulation in the human menstrual cycle is triggered by a surge of:
(a) LH (b) FSH (c) progesterone (d) oxytocin

Accepted Answer

(a) LH.

A sharp surge of luteinising hormone (LH) from the anterior pituitary around day 14 ruptures the mature Graafian follicle and releases the secondary oocyte. FSH earlier grows the follicle.

Question 14

Fertilisation in humans normally occurs in the:
(a) ampulla of the fallopian tube (b) uterus (c) ovary (d) cervix

Accepted Answer

(a) ampulla of the fallopian tube.

The sperm meets and fuses with the secondary oocyte in the ampulla (the wider part of the oviduct). The zygote then travels to the uterus to implant.

Question 15

The hormone detected in pregnancy tests, which maintains the corpus luteum early in pregnancy, is:
(a) hCG (b) LH (c) FSH (d) prolactin

Accepted Answer

(a) hCG.

Human chorionic gonadotropin (hCG), secreted by the developing placenta, maintains the corpus luteum so that progesterone continues in early pregnancy. Its presence in urine is the basis of pregnancy tests.

Practice — Reproduction in Plants and Humans

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