📘Class 10 Science – Chapter: How do Organisms Reproduce? Notes
🌱 Introduction
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Reproduction is the biological process by which new organisms are produced from existing organisms.
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Essential for continuation of species.
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Two main types:
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Asexual reproduction
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Sexual reproduction
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🐟 Asexual Reproduction
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Involves a single parent.
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Offspring are genetically identical (clones).
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Common in unicellular organisms and some multicellular organisms.
Methods of Asexual Reproduction:
| Method | Description | Example |
|---|---|---|
| Binary Fission | Parent splits into two equal halves | Amoeba, Bacteria |
| Budding | New organism develops from a bud | Hydra, Yeast |
| Spore Formation | Spores germinate under suitable conditions | Rhizopus (fungus) |
| Fragmentation | Organism breaks into parts that grow | Spirogyra |
| Regeneration | Lost parts develop into new organisms | Planaria, Starfish |
| Vegetative Propagation | New plants from roots, stems, leaves | Potato, Bryophyllum |
Example: In Hydra, buds develop as outgrowths and later detach.
🌿 Vegetative Propagation in Plants
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A form of asexual reproduction in plants.
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Parts used: roots, stems, leaves.
Natural Methods:
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Roots: Sweet potato
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Stems: Potato (tubers), Ginger (rhizomes)
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Leaves: Bryophyllum (leaf buds)
Artificial Methods:
| Method | Description | Example |
|---|---|---|
| Cutting | Cutting stem and planting it | Rose |
| Layering | Branch bent and covered with soil | Jasmine |
| Grafting | Joining parts of two plants | Mango |
Advantage: Identical quality and faster propagation.
👶 Sexual Reproduction
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Involves two parents: male and female.
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Offspring are genetically different.
Sexual Reproduction in Plants:
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Stamens: Male reproductive part
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Carpels/Pistil: Female reproductive part
Steps:
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Pollination: Transfer of pollen from anther to stigma.
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Fertilization: Male gamete fuses with female gamete.
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Zygote forms → embryo → seed → new plant.
Types of Pollination:
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Self-pollination: Same flower or same plant.
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Cross-pollination: Between two different plants.
👩👦 Sexual Reproduction in Humans
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Involves fusion of male and female gametes.
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Fertilization occurs internally.
Male Reproductive System:
| Organ | Function |
|---|---|
| Testes | Produce sperm and testosterone |
| Vas deferens | Transport sperms |
| Urethra | Passes semen and urine |
| Penis | Transfers sperm into female body |
Female Reproductive System:
| Organ | Function |
|---|---|
| Ovaries | Produce eggs (ova) and hormones |
| Fallopian Tube | Fertilization occurs here |
| Uterus | Development of embryo |
| Vagina | Receives sperm; birth canal |
Fertilization:
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Sperm + Egg → Zygote
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Zygote divides → Embryo → Fetus → Baby
🌸 Reproductive Health
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Awareness about safe sex practices and birth control.
Methods of Contraception:
| Method | Example/Tool | Function |
|---|---|---|
| Barrier Method | Condom, Diaphragm | Prevents sperm entry |
| Chemical Method | Pills, Spermicides | Alters hormonal cycle |
| Surgical Method | Vasectomy, Tubectomy | Permanent solution |
Example: Condoms prevent STDs and unwanted pregnancy.