How do Organisms Reproduce Class 10 Notes (2026-27) — CBSE
Class 10 Science Chapter 7 notes: asexual reproduction, sexual reproduction in flowering plants and humans, reproductive systems, and reproductive health.
How do Organisms Reproduce? — Class 10 Science Notes
Chapter Snapshot
Reproduction is how organisms produce new individuals of their own kind and pass on their DNA. This chapter covers asexual reproduction (one parent, identical offspring), sexual reproduction in flowering plants and in humans (two parents, variation), and reproductive health.
Board relevance: dependable source of a labelled-diagram question (flower or human reproductive system) and a reproductive-health question. Learn the flower parts and the two reproductive systems.
Key Concepts & Definitions
Why reproduce? To continue the species. Reproduction copies DNA; small copying errors create variations, which help a species survive changing environments. Asexual reproduction gives near-identical copies; sexual reproduction combines DNA from two parents, giving greater variation.
Asexual Reproduction (one parent)
Mode Description Example
Binary fission Parent splits into two Amoeba, Leishmania (along a fixed plane)
Multiple fission Splits into many at once Plasmodium
Budding A bud grows on the parent and detaches Hydra, yeast
Fragmentation Body breaks into pieces, each grows Spirogyra
Regeneration A full organism grows from a body part Planaria, Hydra
Spore formation Spores in a sporangium germinate into new organisms Rhizopus (bread mould)
Vegetative propagation New plants from roots, stems, leaves Potato (eyes), Bryophyllum (leaf buds), sugarcane; artificial: cutting, layering, grafting, tissue culture
Advantages of vegetative propagation: plants bear flowers/fruit earlier, and genetically identical (desirable) plants can be grown (e.g. banana, rose, jasmine which have lost the ability to make seeds).
Tissue culture — growing a whole plant from a small tissue/cell sample on a nutrient medium (used to grow ornamental plants quickly).
Sexual Reproduction in Flowering Plants
The flower is the reproductive part. Parts:
- Sepals — green, protect the bud.
- Petals — coloured, attract pollinators.
- Stamen (male) — anther (makes pollen) + filament.
- Carpel/Pistil (female) — stigma (receives pollen) + style + ovary (contains ovules with egg cells).
A bisexual flower has both stamen and carpel (e.g. hibiscus); a unisexual flower has only one (e.g. papaya).
Pollination — transfer of pollen from anther to stigma. Self-pollination (same/related flower) or cross-pollination (different plant, by wind, water, or insects).
Fertilisation — the pollen grows a pollen tube down the style to the ovule; the male gamete fuses with the egg to form a zygote. Afterwards: ovule → seed, ovary → fruit. The seed contains the embryo; germination produces a new plant.
Sexual Reproduction in Humans
At puberty, the body matures to reproduce. Signs include growth of body hair, and (in girls) onset of menstruation and breast development; (in boys) deepening voice and facial hair.
Male reproductive system:
- Testes (in the scrotum, outside the body for a lower temperature) — make sperm and the hormone testosterone.
- Vas deferens carries sperm; glands (prostate, seminal vesicles) add fluid to form semen; the urethra carries semen out.
Female reproductive system:
- Ovaries — produce eggs (ova) and the hormone oestrogen; one egg is released each month.
- Fallopian tube (oviduct) — carries the egg; fertilisation happens here.
- Uterus — where the fertilised egg (embryo) implants and develops.
- Vagina — receives sperm; the birth canal.
Fertilisation to birth: sperm meets egg in the oviduct → zygote → embryo travels to the uterus and implants in its lining → the placenta supplies oxygen and nutrients and removes waste → the baby develops over about 9 months (gestation).
Menstruation: if the egg is not fertilised, the thickened uterus lining breaks down and is shed with blood through the vagina — the monthly cycle (about every 28 days, lasting 2–8 days).
Reproductive Health
Contraception prevents unwanted pregnancy:
Method How it works
Barrier (condoms) Physically stop sperm reaching the egg; also prevent STDs
Hormonal (oral pills) Change hormone balance to stop egg release
IUD (Copper-T) Placed in the uterus to prevent pregnancy
Surgical (vasectomy/tubectomy) Block the vas deferens/oviduct permanently
Sexually Transmitted Diseases (STDs): bacterial (gonorrhoea, syphilis) and viral (HIV/AIDS, warts). Condoms help prevent their spread.
Social aspect: prenatal sex determination is banned by law in India to stop female foeticide and to maintain a healthy sex ratio.
Key Facts
Quick facts boards ask directly:
Topic Fact to remember
Binary fission Amoeba
Multiple fission Plasmodium
Budding Hydra, yeast
Fragmentation Spirogyra
Regeneration Planaria
Spore formation Rhizopus
Male part of flower Stamen (anther + filament)
Female part of flower Carpel (stigma + style + ovary)
Anther → stigma transfer Pollination
Male + female gamete fusion Fertilisation
Ovule becomes Seed
Ovary becomes Fruit
Male gonad; makes Testis; sperm + testosterone
Female gonad; makes Ovary; egg + oestrogen
Fertilisation site in humans Fallopian tube (oviduct)
Nutrient exchange organ Placenta
Human gestation ~9 months
Two definitions to quote: Vegetative propagation — producing new plants from a vegetative part (root, stem, or leaf) of the parent. Menstruation — the monthly shedding of the uterine lining with blood when the egg is not fertilised.
Important Question Patterns
1. Asexual modes (2–3 marks): match mode to organism; why offspring are identical; advantages of vegetative propagation.
2. Flower & plant reproduction (3 marks): label the flower; pollination vs fertilisation; what the ovule and ovary become.
3. Human reproductive system (3–5 marks): label the male/female system; functions of testes, ovary, oviduct, uterus, placenta.
4. Menstruation (2 marks): what it is, why it occurs, its link to fertilisation.
5. Reproductive health (2–3 marks): contraceptive methods; STD prevention; why sex determination is banned.
⚡ Quick Revision
- Reproduction copies DNA; errors → variation → survival advantage. Asexual = 1 parent, identical; sexual = 2 parents, varied.
- Asexual modes: binary fission (Amoeba), multiple fission (Plasmodium), budding (Hydra/yeast), fragmentation (Spirogyra), regeneration (Planaria), spores (Rhizopus), vegetative propagation (potato, grafting, tissue culture).
- Flower: stamen (anther + filament) = male; carpel (stigma + style + ovary) = female. Pollination (anther→stigma) then fertilisation → zygote. Ovule → seed, ovary → fruit.
- Male: testes (sperm + testosterone). Female: ovary (egg + oestrogen), oviduct (fertilisation site), uterus (development), placenta (nutrient exchange). Gestation ≈ 9 months.
- Menstruation: shedding of uterus lining if no fertilisation (~28-day cycle).
- Contraception: barrier (condom, also stops STDs), hormonal pills, Copper-T (IUD), surgical. STDs: gonorrhoea, syphilis, HIV/AIDS. Prenatal sex determination is illegal.
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