REVISION NOTES
Chapter: Reproduction in Animals
1. Reproduction
Reproduction is the process by which organisms produce new individuals of the same kind.
It ensures continuation of species from generation to generation.
2. Modes of Reproduction
Animals reproduce in two ways:
Sexual Reproduction
Asexual Reproduction
3. Sexual Reproduction
Reproduction involving fusion of male and female gametes.
The fused cell is called zygote.
Gametes
| Type | Produced by | Name |
|---|---|---|
| Male gamete | Testes | Sperm |
| Female gamete | Ovary | Ovum (Egg) |
4. Male Reproductive Organs
Main parts:
Testes – Produce sperms
Sperm ducts – Carry sperms
Penis – Transfers sperms into female body
Sperm Structure
Parts of sperm:
Head
Middle piece
Tail
Function of tail: Helps sperm swim towards egg.
5. Female Reproductive Organs
Main parts:
Ovaries – Produce ova (eggs)
Oviducts (Fallopian tubes) – Carry eggs
Uterus – Development of baby takes place here
6. Fertilisation
Fusion of sperm and ovum is called fertilisation.
It forms a zygote.
8 BS CH 4 REPRODUCTION OCR
Types of Fertilisation
| Type | Description | Examples |
|---|---|---|
| Internal fertilisation | Occurs inside female body | Humans, cows, dogs, hens |
| External fertilisation | Occurs outside female body | Frogs, fish, starfish |
7. Development of Embryo
Steps:
Zygote forms
Zygote divides repeatedly
Forms embryo
Embryo attaches to uterus wall
Embryo develops body parts
Stage with identifiable body parts is called foetus
8. Birth of Young Ones
Two types of animals:
| Type | Meaning | Examples |
|---|---|---|
| Viviparous animals | Give birth to young ones | Humans, cows, dogs |
| Oviparous animals | Lay eggs | Hen, frog, lizard, butterfly |
9. Development in Egg (Example: Hen)
Steps:
Fertilisation occurs inside hen.
Protective layers form around embryo.
Hard shell forms around egg.
Hen lays egg.
Chick develops in about 3 weeks.
Chick breaks egg shell and comes out.
10. Metamorphosis
Transformation of larva into adult through drastic changes is called metamorphosis.
Examples
Frog
Butterfly
Silkworm
Frog Life Cycle
Egg → Tadpole → Adult frog
11. Asexual Reproduction
Reproduction involving only one parent.
No fusion of gametes occurs.
12. Types of Asexual Reproduction
1. Budding (Hydra)
New organism develops as bud on parent body.
Bud grows and separates to form new individual.
Example: Hydra
2. Binary Fission (Amoeba)
Parent organism divides into two equal individuals.
Steps:
Nucleus divides
Cytoplasm divides
Two daughter amoebae formed
Example: Amoeba
13. Cloning
Cloning is production of an exact copy of an organism.
Example:
Dolly sheep – First cloned mammal (1996).
14. Test Tube Baby (IVF)
Fertilisation done outside the body in laboratory.
Process called In Vitro Fertilisation (IVF).
Embryo later placed in uterus for development.