Q.(a)
You're viewing a preview — the full solution, concept, methods & PYQ mapping are locked.
Start your 14-day free trial to unlock the full solution →Concept understanding — Male And Female Gametophyte
Let’s start with something you already know. Think of a plant like a mango tree. It produces flowers, and those flowers eventually turn into mangoes. How does that happen? The flower is the plant’s reproductive organ, and inside it, two tiny but crucial structures are made: the male gametophyte and the female gametophyte. These are not the “male” and “female” parts of the flower themselves (like the stamen and pistil) — they are the microscopic, single-generation cells that actually carry the genetic material to form the next plant.
The everyday intuition
Imagine you are baking a cake. The male gametophyte is like the packet of dry yeast — it’s small, mobile, and needs to be added to the mixture. The female gametophyte is like the bowl of flour, eggs, and sugar — it’s larger, stationary, and provides the environment where the yeast works. Without the yeast reaching the bowl, no cake rises. Without the bowl, the yeast has nothing to act on. In a flower, the male gametophyte (pollen grain) must travel to the female gametophyte (embryo sac) for fertilisation to happen.
The precise meaning
In NCERT biology, the male gametophyte is the pollen grain. It develops inside the anther (the top part of the stamen). A mature pollen grain contains two cells: a tube cell and a generative cell. The tube cell will grow a long tube down the style of the pistil, and the generative cell will divide to form two sperm cells. So the male gametophyte is not the whole stamen — it’s the tiny, single-celled (or two-celled) structure that carries the male genetic material.
The female gametophyte is the embryo sac. It develops inside the ovule, which is located in the ovary of the pistil. The embryo sac is a seven-celled, eight-nucleate structure (though you don’t need to memorise numbers for a prose subject — just know it’s a small, organised sac). It contains the egg cell (the female gamete) and other cells that help in fertilisation and nourishment. The female gametophyte is not the whole pistil — it’s the microscopic sac inside the ovule.
The male gametophyte (pollen grain) is haploid — it has only one set of chromosomes. The female gametophyte (embryo sac) is also haploid. When they fuse during fertilisation, they form a diploid zygote, which grows into the seed. This is why both are called “gametophytes” — they produce gametes (sperm and egg).
Why it matters …
Part (a): the microspore undergoes two mitoses (→ vegetative + generative cell, then two male gametes) to form the 3-celled male gametophyte.
Part (b): human primary follicles form before birth; an LH surge causes ovulation, then the corpus luteum secretes progesterone, and its degeneration (no pregnancy) triggers menstruation.
Within the anther's microsporangia, diploid microspore mother cells (pollen mother cells) undergo meiosis to form tetrads of haploid microspores. Each microspore is the first cell of the male gametophyte, protected by a resistant exine and an inner intine.
The microspore nucleus then divides mitotically to give an unequal pair of cells: a large vegetative (tube) cell, rich in reserves and destined to form the pollen tube, and a small generative cell that is engulfed within the vegetative cell's cytoplasm. In most angiosperms this 2-celled stage is what is shed as the pollen grain. The generative cell divides once more (mitosis) to produce two non-motile male gametes, yielding a 3-celled pollen grain. In plants shed at the 2-celled stage, this division happens later in the pollen tube.
A labelled diagram of the 3-celled male gametophyte shows the pollen wall (exine + intine) enclosing a single vegetative cell with a large irregular nucleus and, within its cytoplasm, two spindle-shaped male gametes.
The male gametophyte is highly reduced — it has no free-living existence and its only job is to deliver two male gametes to the embryo sac (one fuses with the egg, the other with the central cell — double fertilisation).
Concept understanding — Human Reproduction
Human Reproduction: A First Look
Think about what makes you you. You have your mother's eyes, your father's laugh, a mix of traits from two people you may never have met — your grandparents. That chain of life, stretching back thousands of years, runs through one process: human reproduction. It is not a topic for biology students alone. It is the story of how every single person on this planet came to be here.
The Big Picture: Why Does Reproduction Exist?
Every living thing has one fundamental drive: to continue its kind. A mango tree grows fruit so its seeds can sprout elsewhere. A bacterium splits in two. For humans, reproduction is more complex — and more personal. It is the reason families exist, why you have siblings or cousins, and why populations grow or shrink.
At its simplest, human reproduction is the biological process by which a new human individual is created. It requires two parents — a male and a female — each contributing a special cell that fuses to form a single, new cell. That single cell then grows, divides, and develops into a baby over about nine months.
Reproduction is not the same as sex. Sex is an act; reproduction is the entire sequence from cell fusion to birth. Not every act of sex leads to reproduction, and reproduction can sometimes happen with medical help (like IVF) without sex.
The Two Key Players: Male and Female Reproductive Systems
Your body, whether male or female, has a set of organs designed specifically for reproduction. These are not the same as the organs that keep you alive — they are the "spare set" dedicated to creating the next generation.
The Male System: Production and Delivery
The male reproductive system has one main job: to produce male sex cells (sperm) and deliver them to the female body. The key parts are:
- Testes (two oval organs in a pouch called the scrotum): These are the factories. They produce sperm continuously from puberty onwards — millions every day. They also produce testosterone, the hormone that drives male physical changes at puberty.
- Duct system (a series of tubes): Sperm travel from the testes through a long coiled tube (epididymis) where they mature, then through a muscular tube (vas deferens) that carries them toward the urethra.
- Accessory glands (seminal vesicles, prostate gland, bulbourethral glands): These add fluids to the sperm to nourish them and help them swim. The mixture of sperm and these fluids is called semen.
- Penis: The organ that delivers semen into the female reproductive tract.
The Female System: Production, Reception, and Nurturing
The female system has a bigger job: it produces female sex cells (eggs), receives sperm, and if fertilization occurs, houses and nourishes the developing baby for nine months. The key parts are:
- Ovaries (two almond-sized organs): These produce eggs — but unlike sperm, eggs are not made continuously. A female is born with all the eggs she will ever have (about 1–2 million at birth, reducing to around 300,000–400,000 by puberty). Each month, one egg matures and is released.
- Fallopian tubes (also called oviducts): These are not connected directly to the ovaries. When an egg is released, the finger-like ends of the tube sweep it inside. Fertilization — the meeting of sperm and egg — happens here, in the tube.
- Uterus (womb): A hollow, pear-shaped muscular organ. If fertilization happens, the embryo implants in the lining of the uterus and grows here. If not, the lining is shed — that is menstruation.
- Cervix: The lower, narrow part of the uterus that opens into the vagina. It produces mucus that changes consistency during the month to help or hinder sperm.
- Vagina: A muscular canal that receives the penis during intercourse and serves as the birth canal during delivery.
The female reproductive system has a monthly cycle (the menstrual cycle) that prepares the body for a possible pregnancy. This cycle is controlled by hormones and typically lasts about 28 days. The release of the egg (ovulation) happens around day 14. If no pregnancy occurs, the uterine lining is shed as menstrual blood — this is a normal, healthy process, not a "curse" or something to be ashamed of.
The Moment of Creation: Fertilization
When sperm from the male meet the egg from the female inside a fallopian tube, one sperm may penetrate the egg's outer layer. That single moment — fertilization — creates a new cell called a zygote. This zygote contains 23 chromosomes from the mother and 23 from the father, making 46 in total. That is the complete genetic blueprint for a new human being.
The zygote immediately begins to divide as it travels down the fallopian tube toward the uterus. By the time it reaches the uterus (about 5–7 days later), it has become a ball of about 100 cells called a blastocyst. This blastocyst burrows into the soft, thick lining of the uterus — a process called implantation. That is when pregnancy truly begins.
The Nine-Month Journey: Development
Once implanted, the developing human is called an embryo for the first eight weeks, and then a fetus from the ninth week until birth. During these months:
- A special organ called the placenta develops, connecting the mother's blood supply to the fetus. It delivers oxygen and nutrients and removes waste — without the mother's and baby's blood ever mixing directly.
- The umbilical cord links the baby to the placenta.
- The baby is protected by a fluid-filled sac (amniotic sac) that cushions it.
- All major organs form in the first three months (first trimester). The next three months (second trimester) are about growth and refinement. The final three months (third trimester) are about rapid weight gain and preparation for life outside the womb. …
Part (a): the microspore undergoes two mitoses (→ vegetative + generative cell, then two male gametes) to form the 3-celled male gametophyte.
Part (b): human primary follicles form before birth; an LH surge causes ovulation, then the corpus luteum secretes progesterone, and its degeneration (no pregnancy) triggers menstruation.
(i) A sectional view of the ovary shows an outer cortex packed with follicles at different stages and an inner medulla with connective tissue and blood vessels. Label the small single-layered primary follicle, the large antral tertiary (Graafian) follicle, the ovum within it, and the blood vessels.
(ii) The primary follicles are formed during fetal (embryonic) life. In a female fetus the ovaries contain a large number of primordial follicles; many degenerate, and those remaining are already at the primary-follicle stage at birth. No new primary follicles are formed after birth — a female is born with her full complement.
(iii) Ovulation is triggered by a mid-cycle surge of luteinising hormone (LH) (around day 14 of a 28-day cycle) from the anterior pituitary. The surge ruptures the mature Graafian follicle, releasing the secondary oocyte into the fallopian tube — this is ovulation. The remaining follicular and thecal cells are reorganised into the corpus luteum under LH influence. …
Unlock everything free for 14 days
- Full step-by-step solutions
- Concept-first explanations
- Methods, shortcuts & mistakes
- PYQ mapping + timed mock tests
Full access for 14 days. No credit card required.