eproduction in Animals – Class 8 Science Notes
Introduction
Reproduction is the biological process by which living organisms produce new individuals of the same kind. It helps in the continuation of species and maintains balance in nature.
Animals reproduce mainly in two ways:
- Sexual Reproduction
- Asexual Reproduction
1. Sexual Reproduction
Sexual reproduction involves two parents, a male and a female.
Gametes
- Male gamete: Sperm
- Female gamete: Ovum (egg)
These gametes are produced in reproductive organs.
Male Reproductive System
The male reproductive system consists of:
- Testes – Produce sperms
- Sperm ducts – Carry sperms
- Penis – Transfers sperms into the female body
👉 Sperms are microscopic, motile cells with a tail for movement.
Female Reproductive System
The female reproductive system consists of:
- Ovaries – Produce eggs (ova)
- Oviducts (Fallopian tubes) – Carry eggs and site of fertilisation
- Uterus – Where the embryo develops
- Vagina – Birth canal
Fertilisation
Fertilisation is the process of fusion of sperm and ovum.
- It results in the formation of a zygote
- Occurs in the oviduct in humans
Types of Fertilisation
- Internal Fertilisation
- Occurs inside the female body
- Example: Humans, dogs, cows
- External Fertilisation
- Occurs outside the body
- Example: Frogs, fish
Development of Embryo
- The zygote divides repeatedly to form an embryo
- The embryo gets embedded in the uterus
- It gradually develops organs and becomes a foetus
- After full development, the baby is born
Viviparous and Oviparous Animals
Viviparous Animals
- Give birth to young ones
- Example: Humans, dogs, cats
Oviparous Animals
- Lay eggs
- Example: Birds, reptiles, frogs
Asexual Reproduction
Asexual reproduction involves only one parent.
Types of Asexual Reproduction
1. Binary Fission
- One organism divides into two
- Example: Amoeba
2. Budding
- A small bud grows and separates
- Example: Hydra
Cloning
Cloning is the production of an exact copy of an organism.
- Dolly, the sheep, was the first cloned mammal
- Cloning is done using special scientific techniques
Importance of Reproduction
- Maintains continuity of life
- Prevents extinction of species
- Produces variations (in sexual reproduction)
Key Terms
- Reproduction – Process of producing young ones
- Gamete – Reproductive cell
- Fertilisation – Fusion of gametes
- Zygote – Fertilised egg
- Embryo – Early stage of development
- Foetus – Developed embryo
One Word Answers for Exams
- Process of producing young ones – Reproduction
- Male reproductive cell – Sperm
- Female reproductive cell – Ovum
- Fusion of sperm and ovum – Fertilisation
- Fertilised egg – Zygote
- Early stage of development – Embryo
- Fully developed embryo – Foetus
- Organ where embryo develops – Uterus
- Tube where fertilisation occurs – Oviduct
- Organ producing sperms – Testes
- Organ producing eggs – Ovary
- Tail-like structure helping sperm movement – Flagellum
- Animals giving birth to young ones – Viviparous
- Animals laying eggs – Oviparous
- Fertilisation inside female body – Internal
- Fertilisation outside body – External
- Reproduction involving two parents – Sexual
- Reproduction involving one parent – Asexual
- Asexual reproduction in Amoeba – Fission
- Asexual reproduction in Hydra – Budding
- First cloned mammal – Dolly
- Exact copy of an organism – Clone
- Site of sperm production – Testes
- Birth canal in females – Vagina
- Developmental stage before foetus – Embryo
- Microscopic male gamete – Sperm
- Cell formed after fertilisation – Zygote
- Reproductive organ in males – Penis
- Reproductive organ carrying egg – Oviduct
- Animal showing external fertilisation – Frog