How do Organisms Reproduce Topic Hub

How do Organisms Reproduce — Class 10 Notes

CBSE 2027 — dates, rules and official papers →
Biology · Ch 7Class 10 · CBSE 2026–27High weightage

How do Organisms Reproduce?

What the board actually asks: draw-and-label diagrams (longitudinal section of a flower, the human male and female reproductive systems), the asexual modes traced stage-by-stage (fission, budding, fragmentation, regeneration, spore formation, vegetative propagation), clear "difference between" answers (pollination vs fertilisation, binary vs multiple fission, self- vs cross-pollination), why DNA copying and variation matter, why menstruation occurs, and the basics of contraception and reproductive health - a high-weight Biology chapter examined heavily through labelled figures and reasoning.

NCERT VERBATIM sourced, word-for-wordAUTHORED LazyTopper teaching scaffolding
The Big Idea AUTHORED

Every organism makes copies of itself - some need one parent, some need two.

Reproduction is the one life process a single organism can live without, yet it is what keeps a species going. It always begins with a cell copying its DNA - the blueprint of body design - and the small errors in that copying create variation. Simple organisms reproduce asexually from one parent (fission, budding, fragmentation, regeneration, spore formation, vegetative propagation); more complex organisms use sexual reproduction, combining germ-cells from two parents so offspring carry a fresh mix of DNA. In Class 10 this chapter is mostly examined through labelled diagrams and stage-by-stage explanations, so most marks reward the exact NCERT terms and correctly labelled structures.

Formulae
Asexual modes (single parent)
Fission · Budding · Fragmentation · Regeneration · Spore formation · Vegetative propagation - offspring genetically identical to the parent
Tip: Offspring are genetically similar to the parent.
Fission types
Binary fission = 2 daughter cells (Amoeba, in any plane); Multiple fission = many daughters at once (Plasmodium)
Tip: Amoeba: binary; Plasmodium: multiple.
Flower parts
Male = Stamen (Anther + Filament) makes pollen; Female = Pistil (Stigma + Style + Ovary with ovules/egg)
Tip: Stamen = male; pistil = female.
Pollination vs Fertilisation
Pollination = pollen transferred anther → stigma; Fertilisation = male germ-cell fuses with egg → zygote
Tip: Pollination is the transfer; fertilisation is the fusion.
Male reproductive system
Testes (in scrotum) → vas deferens → (prostate + seminal vesicle secretions) → urethra → penis
Female reproductive system
Ovary → oviduct / fallopian tube (site of fertilisation) → uterus → cervix → vagina
Egg & menstrual cycle
One egg released per month; unfertilised egg lives about 1 day; menstruation lasts about 2-8 days; development takes about 9 months
Contraception categories
Barrier (condom) · Intra-uterine device (copper-T/loop) · Hormonal (oral pills) · Surgical (block vas deferens or fallopian tube) - condom also lowers STD transmission
Asexual Reproduction: Modes and Examples (Table)
Fission: Amoeba (binary), Plasmodium (multiple)
Fragmentation: Spirogyra
Regeneration: Hydra, Planaria
Budding: Hydra, yeast
Vegetative propagation: Bryophyllum (leaf); layering, grafting (sugarcane, rose, grapes)
Spore formation: Rhizopus
After Fertilisation in a Flower
The zygote divides to form an embryo inside the ovule. The ovule develops a tough coat and becomes the seed; the ovary ripens into the fruit; the other flower parts wither and fall. The seed germinates into a new plant under suitable conditions.
Pollen Tube and Fertilisation in Plants
Pollen lands on the stigma. A pollen tube grows through the style to the ovary and reaches the ovule. The male gamete travels down the tube and fuses with the egg to form the zygote.
Puberty: Changes in Boys and Girls
Both boys and girls: thick hair appears in new parts of the body (armpits, genital area), thinner hair on legs, arms and face; the skin becomes oily and pimples may appear; there is a new awareness of one's body. In girls: breast size increases and menstruation begins. In boys: thick hair grows on the face and the voice cracks. The testes make testosterone. The changes come slowly, over months and years, and not at the same age in everyone.
Placenta and Development of the Embryo
The embryo is implanted in the lining of the uterus. The placenta, a disc embedded in the uterine wall, gives the embryo nutrition from the mother's blood and removes waste. Development takes about nine months.
Sexually Transmitted Diseases (STDs)
Bacterial infections: gonorrhoea, syphilis. Viral infections: warts, HIV-AIDS. A condom helps to prevent transmission of many of these infections to some extent.
Reproductive Health: Family Planning and Sex Ratio
Contraceptive methods help in family planning. The female–male sex ratio must be maintained: female foeticide is a serious social problem that has lowered the child sex ratio.
Vegetative Propagation: Why Use It
Plants raised this way bear flowers and fruits earlier than those grown from seeds. Banana, orange, rose and jasmine have lost the capacity to produce seeds and can only be propagated this way. The new plants are genetically similar enough to the parent to have all its characteristics.

Shortcuts & memory tricks →

Definitions the board rewards NCERT VERBATIM

State these in NCERT’s exact words

Reproduction - the basic event (DNA copy)
NCERT verbatim — memorise this exact wording· Ch 7,
“Therefore, a basic event in reproduction is the creation of a DNA copy.”
What it means: Before a cell can reproduce it must first copy its DNA - the blueprint of body design - so this DNA copy is the starting event of all reproduction.
Fission
NCERT verbatim — memorise this exact wording· Ch 7,
“For unicellular organisms, cell division, or fission, leads to the creation of new individuals.”
What it means: In single-celled organisms the whole cell divides - binary fission gives two daughter cells (Amoeba, bacteria), while multiple fission gives many at once (Plasmodium).
Regeneration
NCERT verbatim — memorise this exact wording· Ch 7,
“simple animals like Hydra and Planaria can be cut into any number of pieces and each piece grows into a complete organism. This is known as regeneration.”
What it means: Some simple animals (Hydra, Planaria) can regrow a whole body from a cut piece; specialised cells proliferate and re-form the missing parts. NCERT stresses this is NOT the normal way they reproduce.
Budding
NCERT verbatim — memorise this exact wording· Ch 7,
“In Hydra, a bud develops as an outgrowth due to repeated cell division at one specific site.”
What it means: In Hydra an outgrowth (bud) forms by repeated cell division at one spot, grows into a tiny Hydra, then detaches to become a new independent individual.
Vegetative propagation
NCERT verbatim — memorise this exact wording· Ch 7,
“This property of vegetative propagation is used in methods such as layering or grafting to grow many plants like sugarcane, roses, or grapes for agricultural purposes.”
What it means: New plants are raised from a root, stem or leaf of the parent (layering, grafting, cuttings); all offspring are genetically identical to the parent and can bear flowers and fruit earlier than seed-grown plants.
Asexual reproduction
NCERT verbatim — memorise this exact wording· Ch 7,
“All the modes of reproduction that we have discussed so far allow new generations to be created from a single individual. This is known as asexual reproduction.”
What it means: Reproduction that needs only one parent and makes offspring genetically identical to it - fission, budding, fragmentation, regeneration, spore formation and vegetative propagation are all asexual.
Sexual reproduction
NCERT verbatim — memorise this exact wording· Ch 7,
“Sexual reproduction involves two individuals for the creation of a new individual.”
What it means: Reproduction that needs two parents (male and female); germ-cells from each combine, so the offspring receive a fresh mix of DNA and show greater variation.
Fertilisation
NCERT verbatim — memorise this exact wording· Ch 7,
“This fusion of the germ-cells or fertilisation gives us the zygote which is capable of growing into a new plant.”
What it means: The fusion of the male germ-cell with the female gamete (egg) to form a single cell, the zygote, which grows into a new individual.
Key terms — NCERT verbatim (state word-for-word)
Variation
Variation is thus useful for the survival of species over time. (Ch 7, )
Spores (spore formation)
The blobs are sporangia, which contain cells, or spores, that can eventually develop into new Rhizopus individuals. (Ch 7, )
Pollination
Reproduction in flowering plants involves transfer of pollen grains from the anther to the stigma which is referred to as pollination. (Ch 7, )
Germination
The seed contains the future plant or embryo which develops into a seedling under appropriate conditions. This process is known as germination. (Ch 7, )
Puberty
This period during adolescence is called puberty. (Ch 7, )
Menstruation
This cycle takes place roughly every month and is known as menstruation. It usually lasts for about two to eight days. (Ch 7, )
Placenta
The embryo gets nutrition from the mother's blood with the help of a special tissue called placenta. (Ch 7, )
Must-know concepts AUTHORED FRAMING

…and where they’re tested

Why reproduce? DNA copying and variation
Reproduction is not needed to keep an individual alive, but it keeps the species going. Its most basic event is copying the DNA that carries the body-design blueprint. No copying reaction is perfectly accurate, so each DNA copy carries small variations. Consistent copying keeps a population suited to its niche, while the variations give a few individuals a chance to survive if conditions change.
2-3 mark: importance of DNA copying in reproduction; why variation is useful for a species but not necessarily for the individual.
Asexual reproduction - modes in single and simple organisms
A single parent creates offspring with no fusion of germ-cells. Fission: unicellular organisms split - binary fission (two daughters, Amoeba) or multiple fission (many daughters, Plasmodium). Budding: an outgrowth in Hydra detaches as a new individual. Fragmentation: Spirogyra breaks into pieces that grow. Regeneration: a cut piece of Hydra/Planaria regrows a whole body (not the normal mode of reproduction). Spore formation: Rhizopus sporangia release spores.
NCERT Fig 7.4Budding in Hydra
A bud (labelled) arises as an outgrowth on the parent body, grows its own tentacles, and finally detaches as a new independent Hydra.
how binary fission differs from multiple fission; how spore formation benefits an organism; why complex organisms cannot reproduce by regeneration.
Vegetative propagation and tissue culture
In many plants the root, stem or leaf grows into a new plant. This is used in layering and grafting (sugarcane, roses, grapes) and lets banana, orange, rose and jasmine that no longer make seeds be propagated. Plants raised this way are genetically identical to the parent and flower/fruit earlier. In tissue culture, cells from the growing tip divide to form a callus, which is grown on a hormone medium into disease-free plantlets.
why vegetative propagation is practised for some plants; advantages over growing from seed; the steps of tissue culture.
Why sexual reproduction? Gametes and meiosis
Combining DNA from two individuals creates new combinations of variants faster than copying errors alone. To stop the DNA amount doubling each generation, germ-cells (gametes) are made with half the chromosomes by a cell division called meiosis; fusion at fertilisation restores the full number. The motile germ-cell is the male gamete and the larger, food-storing germ-cell is the female gamete.
advantages of sexual over asexual reproduction; role of meiosis in keeping chromosome number constant; male vs female gamete.
Sexual reproduction in flowering plants
The flower carries the reproductive parts: the stamen (anther + filament) is male and makes pollen; the pistil (stigma, style, ovary with ovules) is female. Pollination transfers pollen from anther to stigma (self- or cross-pollination, by wind, water or animals). A pollen tube grows through the style to the ovary, the male germ-cell fuses with the egg (fertilisation) to form the zygote; the ovule becomes the seed and the ovary ripens into the fruit.
NCERT Fig 7.7Longitudinal section of a flower
The reproductive parts labelled - Pistil (Stigma, Style, Ovary) and Stamen (Anther, Filament), with Petal and Sepal. The most-drawn diagram of this chapter (exercise Q7).
5-mark: draw and label the longitudinal section of a flower; difference between pollination and fertilisation; formation of seed and fruit.
The human reproductive systems and puberty
At puberty, reproductive tissues mature. The male system makes sperms in the testes (in the scrotum, needing a lower temperature); sperms travel through the vas deferens, gain secretions from the prostate and seminal vesicles, and leave via the urethra and penis. The female system makes eggs in the ovaries; an egg travels down the oviduct (fallopian tube) to the uterus, which opens into the vagina through the cervix.
NCERT Fig 7.10Human male reproductive system
The organs labelled - testis (in scrotum), vas deferens, seminal vesicle, prostate gland, bladder, ureter, urethra and penis.
5-mark: label the human male / female reproductive system; functions of the testis, seminal vesicles and prostate; changes at puberty in boys and girls.
Fertilisation, menstruation and reproductive health
If a sperm meets the egg in the oviduct, the zygote implants in the thick uterus lining and is nourished through the placenta for about nine months. If the egg is not fertilised, the unneeded lining breaks down and leaves the body as menstruation. Reproductive health covers avoiding sexually transmitted infections (condoms help) and contraception - barrier methods (condom), intra-uterine devices (the copper-T or loop, placed in the uterus), hormonal pills, and surgical methods that block the vas deferens or fallopian tube.
NCERT Fig 7.11Human female reproductive system
The organs labelled - ovary, oviduct or fallopian tube, uterus, cervix and vagina.
why menstruation occurs; how the embryo is nourished in the mother's body; methods of contraception; how a copper-T does and does not protect.
Worked examples — real solved problems NCERT VERBATIM

Solved exactly as the source does them

Every problem is a real sourced item, quoted verbatim with its page; the step-by-step decoding and mark-logic are LazyTopper-authored coaching.

Example Fig. 7.1(a) walkthrough,
“Trace how a new Amoeba is produced by binary fission. [authored prompt]”
DNA copying.The parent Amoeba first builds a copy of its DNA, since the basic event in reproduction is the creation of a DNA copy.
1 mark
Nuclear division.The nucleus divides into two, so that each future daughter cell will receive a full set of information.
1 mark
Splitting of the cell.The cytoplasm then divides and the cell splits into two; in Amoeba this splitting can take place in any plane, giving two new individuals similar to the parent.
1 mark
Mark-scheme logic (authored): CBSE 3-mark - 1 mark for DNA copying, 1 for division of the nucleus, 1 for splitting of the cytoplasm into two daughter Amoebae (splitting in any plane is the point that distinguishes Amoeba).
Example Fig. 7.4 walkthrough,
“Trace how a new Hydra is produced by budding. [authored prompt]”
Example Figs. 7.7-7.8 walkthrough,
“Trace the events from pollination to seed formation in a flowering plant. [authored prompt]”
Example Fig. 7.10 walkthrough,
“Trace the path of a sperm from where it is made to where it leaves the male body. [authored prompt]”
Example Fig. 7.11 walkthrough,
“Explain what happens to the egg and the uterus lining when the egg is fertilised, and when it is not. [authored prompt]”
Problem-solving strategies AUTHORED
Diagram question?Draw it large, label with straight ruled lines and use the exact NCERT terms - "vas deferens", "seminal vesicle", "oviduct / fallopian tube", "stigma", not slang. The LS of a flower and the two reproductive systems are the most-drawn figures.
"Difference between" asked?Answer in a two-column table - pollination vs fertilisation, binary vs multiple fission, self- vs cross-pollination, asexual vs sexual - one clear point per row scores faster than a paragraph.
Naming / one-word term?Pin the exact word to the exact process: fission (Amoeba), multiple fission (Plasmodium), budding (Hydra, Yeast), fragmentation (Spirogyra), regeneration (Planaria), spore formation (Rhizopus). Examiners award the specific term.
"Why / how" reasoning add-on?Give the reason, not just the fact - e.g. testes lie in the scrotum because sperm formation needs a lower temperature; menstruation occurs because the prepared uterus lining is not needed when the egg is not fertilised.
Common mistakes that cost marks

Where students lose easy marks

Confusing pollination with fertilisation. Pollination = transfer of pollen from anther to stigma; fertilisation = fusion of the male germ-cell with the egg to form the zygote. They are different steps (exercise Q1 asks exactly this).
Saying budding occurs in Amoeba. Amoeba reproduces by binary fission; budding is seen in Yeast and Hydra (exercise MCQ Q1).
Putting the vas deferens in the female reproductive system. The vas deferens is a male organ; the female system has ovary, oviduct/fallopian tube, uterus and vagina (exercise MCQ Q2).
Mixing up binary and multiple fission. Binary fission gives two daughter cells (Amoeba); multiple fission gives many daughter cells at once (Plasmodium).
Calling regeneration a normal method of reproduction. NCERT states regeneration is NOT the same as reproduction, since organisms do not normally depend on being cut up to reproduce.
Forgetting why menstruation happens - it occurs only because the egg is NOT fertilised, so the thick uterus lining is no longer needed and is shed.
Formulae
Asexual modes (single parent)
Fission · Budding · Fragmentation · Regeneration · Spore formation · Vegetative propagation - offspring genetically identical to the parent
Tip: Offspring are genetically similar to the parent.
Fission types
Binary fission = 2 daughter cells (Amoeba, in any plane); Multiple fission = many daughters at once (Plasmodium)
Tip: Amoeba: binary; Plasmodium: multiple.
Flower parts
Male = Stamen (Anther + Filament) makes pollen; Female = Pistil (Stigma + Style + Ovary with ovules/egg)
Tip: Stamen = male; pistil = female.
Pollination vs Fertilisation
Pollination = pollen transferred anther → stigma; Fertilisation = male germ-cell fuses with egg → zygote
Tip: Pollination is the transfer; fertilisation is the fusion.
Male reproductive system
Testes (in scrotum) → vas deferens → (prostate + seminal vesicle secretions) → urethra → penis
Female reproductive system
Ovary → oviduct / fallopian tube (site of fertilisation) → uterus → cervix → vagina
Egg & menstrual cycle
One egg released per month; unfertilised egg lives about 1 day; menstruation lasts about 2-8 days; development takes about 9 months
Contraception categories
Barrier (condom) · Intra-uterine device (copper-T/loop) · Hormonal (oral pills) · Surgical (block vas deferens or fallopian tube) - condom also lowers STD transmission
Asexual Reproduction: Modes and Examples (Table)
Fission: Amoeba (binary), Plasmodium (multiple)
Fragmentation: Spirogyra
Regeneration: Hydra, Planaria
Budding: Hydra, yeast
Vegetative propagation: Bryophyllum (leaf); layering, grafting (sugarcane, rose, grapes)
Spore formation: Rhizopus
After Fertilisation in a Flower
The zygote divides to form an embryo inside the ovule. The ovule develops a tough coat and becomes the seed; the ovary ripens into the fruit; the other flower parts wither and fall. The seed germinates into a new plant under suitable conditions.
Pollen Tube and Fertilisation in Plants
Pollen lands on the stigma. A pollen tube grows through the style to the ovary and reaches the ovule. The male gamete travels down the tube and fuses with the egg to form the zygote.
Puberty: Changes in Boys and Girls
Both boys and girls: thick hair appears in new parts of the body (armpits, genital area), thinner hair on legs, arms and face; the skin becomes oily and pimples may appear; there is a new awareness of one's body. In girls: breast size increases and menstruation begins. In boys: thick hair grows on the face and the voice cracks. The testes make testosterone. The changes come slowly, over months and years, and not at the same age in everyone.
Placenta and Development of the Embryo
The embryo is implanted in the lining of the uterus. The placenta, a disc embedded in the uterine wall, gives the embryo nutrition from the mother's blood and removes waste. Development takes about nine months.
Sexually Transmitted Diseases (STDs)
Bacterial infections: gonorrhoea, syphilis. Viral infections: warts, HIV-AIDS. A condom helps to prevent transmission of many of these infections to some extent.
Reproductive Health: Family Planning and Sex Ratio
Contraceptive methods help in family planning. The female–male sex ratio must be maintained: female foeticide is a serious social problem that has lowered the child sex ratio.
Vegetative Propagation: Why Use It
Plants raised this way bear flowers and fruits earlier than those grown from seeds. Banana, orange, rose and jasmine have lost the capacity to produce seeds and can only be propagated this way. The new plants are genetically similar enough to the parent to have all its characteristics.
Shortcuts & Tricks
Asexual: one parent, genetically similar offspring. Sexual: two gametes, variation.
MCQ / check only: don't write this as working
Pollination (transfer) comes first, fertilisation (fusion) after; do not swap them.
MCQ / check only: don't write this as working
Ovule → seed; ovary → fruit.
MCQ / check only: don't write this as working
Fertilisation occurs in the oviduct; the embryo implants in the uterus.
MCQ / check only: don't write this as working
Label stamen (anther, filament), pistil (stigma, style, ovary with ovule).
Safe in written answers
Memory Tricks
Fatafat Fruit Rakh Bhoola Vahan Sada.
Six asexual modes in NCERT order. F = Fission · F = Fragmentation · R = Regeneration · B = Budding · V = Vegetative propagation · S = Spore formation.
Amoeba do, Plasmodium bahut, Spirogyra tukde, Hydra-Planaria dobara, Hydra-Khameer kali, Bryophyllum patte se, Rhizopus bijanu se.
Which organism, which mode. Amoeba binary fission · Plasmodium multiple fission · Spirogyra fragmentation · Hydra, Planaria regeneration · Hydra, yeast budding · Bryophyllum leaf vegetative propagation · Rhizopus spores.
Sta-MEN = male (anther makes pollen); Pistil = female: Stigma, Style, Ovary.
Flower parts. Sta-MEN: stamen is the male part (anther makes pollen); Pistil: the female part, with stigma (top), style, ovary.
Girta, badhta, pahunchta, milta.
Pollen to zygote. lands on stigma · tube grows through style · reaches ovule · male gamete fuses with egg.
Ovule se Seed, Ovary se Fruit (phal).
After fertilisation. ovule → seed; ovary → fruit.
Tamatar Vatana Urad.
Path of sperm. T = Testes · V = Vas deferens · U = Urethra (prostate, seminal vesicle add secretions on the way).
Anda, naali, ghar, raasta.
Female path. ovary (egg) → oviduct (fertilisation) → uterus (embryo grows) → vagina.
Ek anda, ek din, do se aath din, nau mahine.
Numbers to remember. one egg per month · egg lives about a day · menstruation 2–8 days · development about nine months.
Bina Hichak Itna Samjho.
Four contraceptive categories. B = Barrier (condom) · H = Hormonal (oral pills) · I = loop or copper-T placed in the uterus · S = Surgical (blocking the vas deferens or the fallopian tube).
Jeevanu: Gonorrhoea, Syphilis. Virus: Warts, HIV-AIDS.
Infections by cause. bacterial: gonorrhoea, syphilis; viral: warts, HIV-AIDS.
Mindmap
      • Basic event = making a DNA copy
      • Copying is not perfect → variation
      • Variation helps a species survive changing niches
      • Not essential for the individual, but keeps the species going
      • Fission - binary (Amoeba), multiple (Plasmodium)
      • Budding (Hydra, Yeast)
      • Fragmentation (Spirogyra)
      • Regeneration (Hydra, Planaria) - not a normal mode
      • Spore formation (Rhizopus)
      • Vegetative propagation + tissue culture
      • Flower - stamen (male), pistil (female)
      • Pollination - self / cross (wind, water, animals)
      • Pollen tube → ovary; fertilisation → zygote
      • Ovule → seed, ovary → fruit
      • Puberty - reproductive tissues mature
      • Male - testes, vas deferens, prostate, urethra, penis
      • Female - ovary, oviduct, uterus, cervix, vagina
      • Fertilisation in oviduct → embryo → placenta (~9 months)
      • No fertilisation → menstruation
      • Pollination is NOT fertilisation
      • Vas deferens is a MALE organ
      • Binary (2) vs multiple (many) fission
      • Contraception - barrier, intra-uterine device (copper-T), hormonal, surgical; condom lowers STDs

The diagrams you must be able to draw and label - this chapter is examined heavily through labelled figures. Learn each one in the exact NCERT form, especially the longitudinal section of a flower and the two human reproductive systems.

NCERT Fig 7.1(a)Binary fission in Amoeba
The parent Amoeba copies its DNA, the nucleus divides, and the cell splits into two daughter Amoebae; the splitting can take place in any plane.
NCERT Fig 7.2Multiple fission in Plasmodium
The single-celled malarial parasite divides into many daughter cells simultaneously inside a common membrane - many nuclei form before the cytoplasm splits.
NCERT Fig 7.4Budding in Hydra
A bud (labelled) arises as an outgrowth on the parent body, grows its own tentacles, and finally detaches as a new independent Hydra.

Flower: Longitudinal Section

NCERT Fig 7.7Longitudinal section of a flower
The reproductive parts labelled - Pistil (Stigma, Style, Ovary) and Stamen (Anther, Filament), with Petal and Sepal. The most-drawn diagram of this chapter (exercise Q7).
NCERT Fig 7.8Germination of pollen on stigma
Pollen grains on the stigma grow a pollen tube down through the style, carrying the male germ-cell to the female germ-cell in the ovary. Labels: pollen grain, stigma, male germ-cell, pollen tube, ovary, female germ-cell.
NCERT Fig 7.10Human male reproductive system
The organs labelled - testis (in scrotum), vas deferens, seminal vesicle, prostate gland, bladder, ureter, urethra and penis.
NCERT Fig 7.11Human female reproductive system
The organs labelled - ovary, oviduct or fallopian tube, uterus, cervix and vagina.

3 competency questions from the CBSE board pattern, with the full step-marked solution for each — the marks are shown per step, as the official scheme awards them.

5 marksSection D

(a) Certain specialised cells in animals called stem cells have the ability to divide and differentiate into different cell types. This helps in the replacement of a damaged organ. Name and explain two methods of asexual reproduction that are similar to stem cells and occur mostly in multicellular organisms. (b) Identify TWO pairs of reproductive organs in males and females that are functionally similar to each other. Justify.

Step-marked solution
  1. [1 mark] (a) Regeneration: in some multicellular organisms (e.g. Planaria, Hydra) the cells of a body fragment divide and differentiate to rebuild all the missing body parts — similar to the way stem cells act.
  2. [1 mark] (a) Budding: a small outgrowth (bud) develops on the parent body (e.g. Hydra); its cells divide and differentiate into all the required tissues, and the bud then detaches as a new individual — also stem-cell-like.
  3. [1 mark] (b) Testes (male) and Ovaries (female) are a functionally similar pair — both produce gametes and secrete reproductive hormones (testosterone / oestrogen).
  4. [1 mark] (b) Vas deferens (male) and Fallopian tube / oviduct (female) are a functionally similar pair — both are ducts that transport the gametes towards the site of fertilisation.
  5. [1 mark] Justification: in each pair the two organs perform the same reproductive function in the two sexes, which is why they are described as functionally analogous.
3 marksSection C

Nivedita has dark brown eyes like her mother but the same shaped nose as her father. Explain why Nivedita has features from both of her parents.

Step-marked solution
  1. [1 mark] Features are passed on by inheritance.
  2. [1 mark] She was produced by sexual reproduction, involving both parents.
  3. [1 mark] Genes are transferred from each parent to the offspring, so she shows features of both.
1 markSection A

Two statements are given - one labelled Assertion (A) and the other labelled Reason (R). Read the statements carefully and choose the option that correctly describes statements A and R. Assertion (A): Oral contraceptive pills and copper-T do not prevent sexually transmitted diseases. Reason (R): Sexually transmitted disease are transmitted by contact with mucous membranes of infected organs.

  1. (A) Both A and R are true and R is the correct explanation of A.
  2. (B) Both A and R are true but R is not the correct explanation of A.
  3. (C) A is true but R is false.
  4. (D) A is false but R is true.
Step-marked solution
  1. [1 mark] Correct option: (1) Both A and R are true and R is the correct explanation of A. Neither pills nor copper-T forms a barrier at the mucous membranes, and it is exactly that contact route named in R which explains why these methods cannot prevent transmission.
Practise How do Organisms Reproduce? competency questions

Read NCERT Chapter 7 on LazyTopper (jesc107)

Official NCERT chapter PDF (jesc107) — ncert.nic.in

Sources: NCERT 2026-27 (tap to view)
Source ledger PROVENANCE

Source edition: NCERT Reprint 2026-27, Class 10 Science, Ch 7. One row per sourced item — every verbatim, example and NCERT figure traces to its page.

ItemTypeSource
Reproduction - the basic event (DNA copy)verbatimNCERT 2026-27 Ch7
FissionverbatimNCERT 2026-27 Ch7
RegenerationverbatimNCERT 2026-27 Ch7
BuddingverbatimNCERT 2026-27 Ch7
Vegetative propagationverbatimNCERT 2026-27 Ch7
Asexual reproductionverbatimNCERT 2026-27 Ch7
Sexual reproductionverbatimNCERT 2026-27 Ch7
FertilisationverbatimNCERT 2026-27 Ch7
VariationverbatimNCERT 2026-27 Ch7
Spores (spore formation)verbatimNCERT 2026-27 Ch7
PollinationverbatimNCERT 2026-27 Ch7
GerminationverbatimNCERT 2026-27 Ch7
PubertyverbatimNCERT 2026-27 Ch7
MenstruationverbatimNCERT 2026-27 Ch7
PlacentaverbatimNCERT 2026-27 Ch7
Binary fission in AmoebaexampleNCERT 2026-27 Ch7 Fig 7.1(a)
Budding in HydraexampleNCERT 2026-27 Ch7 Fig 7.4
Fertilisation in a flowerexampleNCERT 2026-27 Ch7 Figs 7.7-7.8 -121
Path of the sperm in the human male reproductive systemexampleNCERT 2026-27 Ch7 Fig 7.10
What happens when the egg is / is not fertilisedexampleNCERT 2026-27 Ch7 Fig 7.11 -124
NCERT Fig 7.1(a)figureNCERT 2026-27 Ch7 7.1(a)
NCERT Fig 7.2figureNCERT 2026-27 Ch7 7.2
NCERT Fig 7.4figureNCERT 2026-27 Ch7 7.4
NCERT Fig 7.7figureNCERT 2026-27 Ch7 7.7
NCERT Fig 7.8figureNCERT 2026-27 Ch7 7.8
NCERT Fig 7.10figureNCERT 2026-27 Ch7 7.10
NCERT Fig 7.11figureNCERT 2026-27 Ch7 7.11

How do Organisms Reproduce? · spec-rendered note · NCERT Reprint 2026-27, Class 10 Science, Ch 7

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