HOW DO ORGANISMS REPRODUCE? 

1. Introduction to Reproduction

Reproduction is the biological process by which living organisms produce new individuals of the same species.

Importance of reproduction

• Maintains continuity of life

• Transfers genetic information to the next generation

• Increases population

• Ensures survival of species

2. Types of Reproduction

There are two main types:

A. Asexual Reproduction

➡️ Involves single parent
➡️ No formation of gametes
➡️ Offspring are genetically identical (clones)

Types of Asexual Reproduction

1. Fission

• Binary fission → Amoeba, Bacteria

• Multiple fission → Plasmodium

2. Budding

• Bud grows on parent body

• Example: Yeast, Hydra

3. Fragmentation

• Body breaks into fragments, each form new organism

• Example: Spirogyra

4. Regeneration

• Regrowth of lost body parts

• Example: Planaria, Starfish

5. Spore formation

• Occurs in fungi

• Example: Rhizopus (bread mould)

• Spores enclosed in sporangia

6. Vegetative Propagation

• Formation of new plants from vegetative parts

Vegetative part	Examples
Stem tuber	Potato
Runners	Grass, Strawberry
Rhizome	Ginger
Leaf	Bryophyllum

B. Sexual Reproduction

➡️ Involves two parents
➡️ Formation of male and female gametes
➡️ Results in variation
➡️ Ensures better adaptability

3. Sexual Reproduction in Plants

Flower

Main reproductive organ.

Parts of flower

1. Stamen (Male)

   • Anther

   • Filament
     Produces pollen grains

2. Carpel/Pistil (Female)

   • Stigma

   • Style

   • Ovary (contains ovules)

Steps of sexual reproduction

1. Pollination

   • Transfer of pollen grains from anther to stigma

   • Types:

     • Self-pollination

     • Cross-pollination

2. Fertilisation

   • Fusion of male and female gametes

3. Seed formation

   • Ovule → Seed

   • Ovary → Fruit

4. Sexual Reproduction in Humans

Male reproductive system

• Testes

• Vas deferens

• Urethra

• Penis

• Accessory glands

Function:
Produces sperm and testosterone.

Female reproductive system

• Ovaries

• Oviducts/Fallopian tubes

• Uterus

• Vagina

Function:
Produces ovum (egg) and oestrogen/progesterone.

Fertilisation in humans

• Happens in fallopian tube

• Zygote → embryo → foetus (in uterus)

5. Menstrual Cycle

Occurs in females every 28 days (average).

Stages:

1. Menstruation (1–5 days)

2. Ovulation (~14th day)

3. If fertilisation occurs → pregnancy

4. If not → cycle repeats

6. Contraception (Birth Control Methods)

• Barrier methods → Condoms

• Oral pills

• Intrauterine devices → Copper-T

• Surgical methods

  • Vasectomy (male)

  • Tubectomy (female)

Purpose:

• Avoid unwanted pregnancy

• Maintain reproductive health

• Prevent STDs (condoms)

7. Reproductive Health

• Awareness of sexually transmitted infections

• Maintaining hygiene

• Balanced diet

• Regular medical check-ups

IMPORTANT QUESTIONS & ANSWERS

1. What is reproduction?

Answer:
Reproduction is the biological process by which organisms produce new individuals of the same species, ensuring continuity of life.

2. What is the difference between asexual and sexual reproduction?

Asexual Reproduction	Sexual Reproduction
One parent	Two parents
No gametes	Gametes involved
No variation	Variations occur
Fast process	Slower process
Example: Amoeba	Example: Humans

3. Explain binary fission in Amoeba.

Answer:
In binary fission, the nucleus of Amoeba divides into two, followed by division of cytoplasm. This forms two identical daughter cells.

4. What is vegetative propagation? Give two examples.

Answer:
Vegetative propagation is a method of asexual reproduction in plants where new plants grow from vegetative parts like stem, root or leaf.
Examples:

• Potato (stem tuber)

• Bryophyllum (leaf)

5. Describe the structure of a flower.

Answer:
A flower has four main parts:

• Sepals

• Petals

• Stamen (male part: anther + filament)

• Carpel (female part: stigma + style + ovary)

6. What is pollination? What are its types?

Answer:
Pollination is the transfer of pollen grains from anther to stigma.
Types:

• Self-pollination

• Cross-pollination

7. What is fertilisation?

Answer:
Fertilisation is the process of fusion of male and female gametes to form a zygote.

8. What changes occur in girls at puberty?

Answer:

• Development of breasts

• Menstruation begins

• Wider hips

• Growth of hair in body parts

9. What is the menstrual cycle?

Answer:
The menstrual cycle is a monthly cycle in females that involves the release of an ovum and preparation of the uterus for pregnancy. Average duration is 28 days.

10. Name any two sexually transmitted diseases.

Answer:

• AIDS

• Syphilis

• Gonorrhoea (any two)

11. What is contraception? Name any two contraceptive methods.

Answer:
Contraception is the method to prevent pregnancy.
Examples:

• Condom

• Oral pills

• Copper-T

12. Why is variation important in organisms?

Answer:
Variation helps organisms adapt to changing environment and increases chances of survival.