CBSE Class 8 Science Chapter 9 Revision Notes
Chapter 8: Reproduction In Animals Revision Notes
Reproduction is the process through which organisms give birth to their own offspring.
MODES OF REPRODUCTION
Animals reproduce in two different ways:
(i) Sexual reproduction and(ii) Asexual reproduction
1. SEXUAL REPRODUCTION
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Sexual reproduction is the process of combining male and female gametes to produce offspring.
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The female reproductive organs are the ovaries, oviducts (fallopian tubes), and uterus.
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Testes, sperm ducts, and the penis are among the male reproductive organs.
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The ovary generates ova, female gametes, while the testes create sperm, male gametes.
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Fertilization is the process of combining the ovum with sperm.
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A zygote is a fertilised egg.
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Internal fertilisation refers to fertilisation that occurs within the female body. This can be seen in humans and other animals, including hens, cows, and dogs.
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External fertilisation refers to fertilisation that occurs outside of the female body. This is seen in frogs (in the water), fish, starfish, and other animals.
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To produce an embryo, the zygote splits several times.
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For future development, the embryo is implanted in the uterine wall.
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The foetus is the embryo stage in which all of the body components can be identified.
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Animals that give birth to offspring, such as humans, cows, and dogs, are viviparous.
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Oviparous animals lay eggs, such as frogs, lizards, and butterflies.
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Metamorphosis is the process of a larva growing into an adult through significant changes (moth to a cocoon).
2. ASEXUAL REPRODUCTION
- Asexual reproduction refers to the process of reproduction in which only one parent is involved.
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Buds in hydra evolve into new individuals. Budding is the term for this type of asexual reproduction.
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Amoeba reproduces by separating the nucleus followed by its body into two halves. Binary fission is the name for this sort of asexual reproduction.
Source: Chapter-9.pmd (ncert.nic.in)
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