Class 12 Biology Chapter 1

Class 12 Biology Chapter 1

Reproduction in Organisms – Important Points Notes

1. Reproduction Kya Hai?

Jeev apne jaise naye jeev banate hain, ise reproduction kehte hain।

Importance

Species ko continue rakhta hai

Population maintain hoti hai

Genetic continuity hoti hai

2. Lifespan (जीवन काल)

Jeev ke janm se natural death tak ka samay lifespan kehlata hai।

Examples

Butterfly → 1-2 weeks

Crow → ~15 years

Banyan tree → hundreds of years

3. Types of Reproduction

(A) Asexual Reproduction

Sirf ek parent

Gamete formation nahi

Offspring genetically same

Fast process

(B) Sexual Reproduction

Do parents

Male + female gamete fusion

Variation hota hai

Evolution me help karta hai

ASEXUAL REPRODUCTION

4. Binary Fission

Ek organism do equal parts me divide hota hai।

Examples

Amoeba

Paramecium

5. Multiple Fission

Ek parent se ek saath kai offspring bante hain।

Example

Plasmodium

6. Budding

Body par bud banta hai jo alag ho jata hai।

Example

Hydra

Yeast

7. Fragmentation

Body tootkar fragments banati hai aur har fragment naya organism banata hai।

Example

Spirogyra

8. Regeneration

Body ka kata hua part pura organism bana leta hai।

Example

Planaria

9. Spore Formation

Spores ke through reproduction hota hai।

Example

Rhizopus (Bread mould)

10. Vegetative Propagation

Plant ka vegetative part naya plant banata hai।

Natural Methods

Potato → tuber

Ginger → rhizome

Onion → bulb

Artificial Methods

Cutting

Layering

Grafting

Tissue culture

11. Clone

Genetically identical organisms ko clone kehte hain।

SEXUAL REPRODUCTION

12. Juvenile Phase

Birth ke baad reproductive maturity tak ka phase।

Plants me

Vegetative phase kehlata hai।

13. Reproductive Phase

Jab organism reproduction kar sakta hai।

Plants me Sign

Flower formation

14. Senescent Phase

Old age phase jahan reproductive capacity kam ho jati hai।

15. Events in Sexual Reproduction

1. Pre-fertilization

Gamete formation

Gamete transfer

2. Fertilization

Male aur female gamete fusion।

3. Post-fertilization

Zygote formation

Embryo development

PRE-FERTILIZATION EVENTS

16. Gametogenesis

Gamete formation process।

Male Gamete

Sperm / pollen grain

Female Gamete

Ovum / egg

17. Homothallic and Bisexual

Same organism male aur female gamete banata hai।

Example

Earthworm

Tapeworm

18. Heterothallic and Unisexual

Male aur female alag organisms me hote hain।

Example

Human

Cockroach

19. Gamete Transfer

Male gamete ko female gamete tak pahunchana।

Plants me

Pollination ke through।

FERTILIZATION

20. Syngamy

Male aur female gamete fusion।

21. External Fertilization

Fusion body ke bahar hota hai।

Example

Frog

Fish

Features

Water required

Zyada gametes produced

22. Internal Fertilization

Fusion body ke andar hota hai।

Example

Human

Birds

Reptiles

Features

Survival chance high

Fewer gametes

POST-FERTILIZATION EVENTS

23. Zygote

Fertilization ke baad formed diploid cell।

24. Embryogenesis

Zygote se embryo formation।

25. Oviparous Animals

Egg lay karte hain।

Example

Birds

26. Viviparous Animals

Direct young ones ko janm dete hain।

Example

Humans

IMPORTANT TERMS

Term Meaning

Gamete Sex cell

Zygote Fertilized egg

Embryo Developing organism

Clone Genetically same organism

Syngamy Gamete fusion

Fertilization Male + female gamete fusion

Most Important NCERT Lines

Reproduction is not essential for survival of individual but essential for continuity of species.

Offspring formed by asexual reproduction are called clones.

Juvenile phase is the period of growth before reproductive maturity.

Embryogenesis refers to development of embryo from zygote.

Syngamy may occur outside or inside the body.

Exam Important Examples

Topic Example

Binary fission Amoeba

Budding Hydra

Fragmentation Spirogyra

Regeneration Planaria

Spore formation Rhizopus

External fertilization Frog

Internal fertilization Human

Very Important Short Questions

Q1. Clone kya hai?

Genetically identical offspring ko clone kehte hain।

Q2. Syngamy kya hai?

Male aur female gamete fusion ko syngamy kehte hain।

Q3. External fertilization example?

Frog।

Q4. Vegetative propagation example?

Potato।

Q5. Embryogenesis kya hai?

Embryo formation process।

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