Reproduction in organisms -class12 biology notes

 📌 What is Reproduction?


Reproduction is the biological process by which living organisms produce offspring similar to themselves.


Types of Reproduction:


1. Asexual Reproduction – Single parent, no gamete involvement.


Examples: Binary Fission (Amoeba), Budding (Hydra)




2. Sexual Reproduction – Two parents, gamete formation, and fusion.


Involves male and female reproductive systems.






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🧪 Lifespans of Organisms:


Defined as the period between birth and natural death.


Mayfly: 1 day


Elephant: 60–70 years


Tortoise: 100–150 years




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🌱 Asexual Reproduction Methods:


Method Example


Binary Fission Amoeba

Budding Hydra, Yeast

Fragmentation Spirogyra

Spore Formation Rhizopus

Vegetative Potato, Ginger




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👫 Sexual Reproduction Stages:


1. Pre-fertilization Events


Gametogenesis


Gamete Transfer




2. Fertilization


Fusion of male and female gametes (zygote formation)




3. Post-fertilization Events


Zygote development


Embryogenesis






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🧬 Important Terms:


Zygote: Single-celled formed after fertilization


Gamete: Reproductive cell (sperm or egg)


Fertilization: Fusion of male and female gametes


Embryo: Early stage of development after zygote




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📖 Quick Revision Points:


Reproduction ensures species survival.


Asexual reproduction is faster but lacks variation.


Sexual reproduction introduces genetic diversity.




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🧠 Tip for Exam:


Draw diagrams of:


Hydra budding


Binary fission in Amoe

ba


Gametogenesis flowchart




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✍️ Written by Shahid


📚 Visit Shahid Notes for more free study materials.

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