Chapter 9: Reproduction in animals

These NCERT Class 8 Science Chapter 9 notes explain reproduction in animals in a simple and structured way. The chapter focuses on how living organisms produce new individuals to ensure continuation of species.

It discusses sexual reproduction involving male and female gametes, fertilisation, formation of zygote and development of embryo. It also explains asexual reproduction methods such as binary fission and budding.

Chapter 9 – Reproduction in Animals is important for understanding life processes and human reproductive system basics. It is highly relevant for school examinations and foundation level competitive preparation.

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1. Introduction: what is reproduction?

• Reproduction is the process by which living organisms produce new individuals of their own kind.
• The new individual produced is called offspring.
• Reproduction ensures continuation of a species.
• It helps maintain balance in nature.
• Just like a family continues through children, animals continue through reproduction.

2. Modes of reproduction in animals

• Animals reproduce by two main methods: sexual reproduction and asexual reproduction.
• Sexual reproduction involves two parents.
• Asexual reproduction involves only one parent.
• Different animals follow different modes based on their body structure.
• Both methods ensure survival of species.

3. Sexual reproduction

• Sexual reproduction involves a male and a female parent.
• Male and female reproductive cells fuse together.
• The male produces sperm, and the female produces ovum.
• Fusion of these cells forms a new individual.
• This method produces variation among offspring.

4. Male reproductive system in humans

• The main parts are testes, sperm ducts and penis.
• Testes produce sperms which are male gametes.
• Testes also produce male hormones.
• Sperms are transported through sperm ducts.
• The male reproductive system helps in fertilisation.

5. Female reproductive system in humans

• The main parts are ovaries, oviducts and uterus.
• Ovaries produce female gametes called ova.
• Oviducts are also known as fallopian tubes.
• The uterus is the organ where the baby develops.
• The female system supports development of the embryo.

6. Gametes and their role

• Gametes are reproductive cells.
• The male gamete is called sperm.
• The female gamete is called ovum or egg.
• Gametes carry genetic information from parents.
• Fusion of gametes leads to formation of new life.

7. Fertilisation and its types

• Fertilisation is the fusion of sperm and ovum.
• It results in the formation of a zygote.
• Internal fertilisation occurs inside the body, as in humans and birds.
• External fertilisation occurs outside the body, as in frogs and fish.
• Type of fertilisation depends on the animal species.

8. Development of embryo

• The zygote divides repeatedly to form an embryo.
• The embryo further develops into a foetus.
• Development occurs inside the uterus in humans.
• The placenta connects mother and foetus.
• Placenta supplies food and oxygen and removes waste.

9. Viviparous and oviparous animals

• Viviparous animals give birth to young ones.
• Humans, cows and dogs are examples of viviparous animals.
• Oviparous animals lay eggs.
• Birds, frogs and fish are examples of oviparous animals.
• The mode of reproduction varies among animals.

10. Asexual reproduction and its types

• Asexual reproduction involves only one parent.
• There is no fusion of gametes in this method.
• Binary fission occurs when one organism divides into two, as in Amoeba.
• Multiple fission occurs when one organism divides into many, as in Plasmodium.
• Budding occurs when a new organism grows as a bud, as in Hydra.

11. Cloning as a special method

• Cloning is the production of an exact copy of an organism.
• The cloned organism is genetically identical.
• Dolly the sheep was the first cloned mammal.
• Cloning is done using advanced scientific techniques.
• It is an example of artificial reproduction.

12. Key exam-oriented keywords explained

• Reproduction: Process of producing new individuals of the same species.
• Sexual reproduction: Reproduction involving fusion of male and female gametes.
• Asexual reproduction: Reproduction involving only one parent without gamete fusion.
• Gametes: Reproductive cells such as sperm and ovum.
• Sperm: Male reproductive cell.
• Ovum: Female reproductive cell.
• Fertilisation: Fusion of sperm and ovum forming a zygote.
• Zygote: Single cell formed after fertilisation.
• Embryo: Early stage of development after zygote division.
• Foetus: Later stage of embryo before birth.
• Placenta: Tissue connecting mother and foetus for nourishment.
• Viviparous: Animals that give birth to young ones.
• Oviparous: Animals that lay eggs.
• Binary fission: Division of one organism into two equal parts.
• Budding: Formation of new organism from a small outgrowth.

13. One-page summary for quick revision

• Reproduction ensures continuation of species.
• Sexual reproduction involves fusion of gametes.
• Fertilisation forms a zygote which develops into embryo and foetus.
• Viviparous animals give birth, while oviparous animals lay eggs.
• Asexual reproduction occurs without fusion of gametes.

Understanding NCERT Class 8 Science Chapter 9 is essential to learn how reproduction ensures continuity of life. The chapter clearly explains fertilisation, development of embryo and different modes of reproduction.

The concepts help students understand human biology and basic life processes. It is highly useful for school exams and foundation competitive preparation.

Continue reading NCERT Class 8 Science Chapter 10 – Reaching the Age of Adolescence to understand changes during puberty and role of hormones.

FAQs

Q1. What is reproduction?
Reproduction is the process by which living organisms produce new individuals of their own kind.

Q2. What is fertilisation?
Fertilisation is the fusion of male and female gametes to form a zygote.

Q3. What is the difference between viviparous and oviparous animals?
Viviparous animals give birth to young ones, while oviparous animals lay eggs.

Q4. What is asexual reproduction?
Asexual reproduction involves only one parent and does not involve fusion of gametes.

Q5. Why is this chapter important for exams?
It explains reproduction, fertilisation and life cycle concepts, which are important for school exams and foundation preparation.

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