Core ConceptRead this first — the foundation of the topic
There are two main types
Asexual Reproduction and Sexual Reproduction.
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TYPE 1: ASEXUAL REPRODUCTION
Only ONE parent is involved. No gametes (sex cells) are needed. Offspring are genetically identical to the parent (called clones)
Modes of Asexual Reproduction
• Binary Fission — Parent splits into TWO equal parts
Example
Amoeba, Bacteria (like Leishmania splits lengthwise)
• Multiple Fission — Parent splits into MANY parts
Example
Plasmodium (malaria parasite)
• Budding — Small bud grows on parent, detaches and forms new organism
Example
Hydra, Yeast
• Fragmentation — Body breaks into pieces, each piece grows into new organism
Example
Spirogyra (algae)
• Regeneration — If an organism is cut, each part can grow into a full organism
Example
Planaria, Starfish
• Spore Formation — Organisms produce spores that germinate into new plants
Example
Rhizopus (bread mould), Ferns, Mosses
• Vegetative Propagation — New plants grow from roots, stems, or leaves
Example
Potato (eyes/buds), Rose (stem cutting), Bryophyllum (leaf margin buds)
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TYPE 2: SEXUAL REPRODUCTION
TWO parents are involved (male and female). Gametes are formed — male gamete (sperm) and female gamete (egg/ovum). Fertilisation joins them to form a zygote. The zygote develops into offspring
Key Terms
• Gamete = Sex cell (sperm or egg)
• Fertilisation = Fusion of male and female gametes
• Zygote = Cell formed after fertilisation
• Internal Fertilisation — inside female body
Example
Humans, Cow, Dog
• External Fertilisation — outside female body, in water
Example
Frog, Fish
In Humans:
• Puberty in girls: Around 10–12 years. Menstruation starts.
• Puberty in boys: Around 13–14 years.
• Menstrual cycle = 28 days
• Gestation period (pregnancy) = 9 months (approximately 280 days)
• Fertilisation occurs in the Fallopian tube
• Implantation occurs in the Uterus
In Plants (Flowers):
• Stamen = Male part (produces pollen = male gamete)
• Pistil/Carpel = Female part (contains ovule = female gamete)
• Pollination = Transfer of pollen from stamen to pistil
• Self-pollination = Same flower or same plant
• Cross-pollination = Different plant of same species
• Fertilisation in plants forms SEED. Ovary becomes FRUIT.
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Formula BlockMemorise — at least one formula appears in every paper
Memory HookRemember this — never confuse the two again
):
Zygote = Male Gamete + Female Gamete
Fruit = Fertilised Ovary | Seed = Fertilised Ovule
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Exam PatternsWhat examiners ask — read before attempting PYQs
RRB Group D asks: Which organism reproduces by budding? / Where does fertilisation occur in humans? / What is the gestation period? / Vegetative propagation examples.
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SHORTCUT/TRICK:
Trick 1 — Remember Budding: 'HY-dra and Yeast = HY-5 = Budding Brothers'
Trick 2 — For plant parts: 'SiPF' = Stamen is Pollen (male), Pistil is Female
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Worked ExampleSolve this step-by-step before moving on
Question: Bread mould reproduces by
When to UseQuickly decide which method to apply in the exam
?
Step 1: Bread mould = Rhizopus fungus
Step 2: Rhizopus produces tiny spore sacs called sporangia
Step 3: These sporangia burst and release spores into air
Step 4: Spores germinate in suitable conditions to form new mould
Answer: Spore Formation
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Exam TrapsCommon mistakes students make — avoid these
Students confuse Regeneration with Fragmentation. Remember — Fragmentation means the organism naturally BREAKS apart (like Spirogyra). Regeneration means an organism can REGROW from a cut piece (like Planaria).
Also, many students think Yeast uses Binary Fission — it does NOT. Yeast uses BUDDING.