Thursday, 21 March 2013

Chapter 9. REPRODUCTIION IN ANIMALS | Solved Exercises | CBSE Class VIII (8th) Science

  • Question 1. Explain the importance of reproduction in organisms.
  • Answer : The process of reproduction in organisms is essential for the continuation of theirs respective species. The reproduction in organisms is very important as it ensures the continuation of similar kinds of individuals, generation after generation.In larger context, reproduction in various species of animals and plants kingdom, forms part of ecosystem and which helps in maintaining it, by evolution chain. 
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  • Question 2. Describe the the process of fertilization in human beings.
  • Answer . In human beings,the reproductive organs in the female include ovaries, oviducts and uterus. The reproductive organs in male include testes, sperm ducts and penis. In human beings, female, produces every month, female gametes called ova inside her ovaries. Ova which is a single matured egg is released into the oviduct by one of the ovaries. The testes in male produce male gametes called sperms. 
  • The fusion of ovum and sperm is called fertilization. The fertilized egg is called a zygote. The zygote divides repeatedly to give rise to an embryo. The embryo gets embedded in the wall of the uterus for further development.The stage of the embryo in which all the body parts are identifiable is called foetus. Human beings and others animals such as cows and dogs which give birth to young ones are called viviparous animals. 
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  • Question 3. Choose the most appropriate
    1. Internal fertilization occurs
      1. in female body.
      2. outside female body.
      3. in male body.
      4. outside male body.
    2. A tadpole develops into an adult frog by the process of
      1. fertilization.
      2. metamorphosis
      3. embedding
      4. budding.
    3. The number of nuclei present in a zygote is
      1. none.
      2. one.
      3. two.
      4. four.
  • Answer .
    1. Internal fertilization occurs - (i) in female body.
    2. A tadpole develops into an adult frog by the process of - (ii) metamorphosis
    3. The number of nuclei present in a zygote is - (ii) one.

  • Question 4. Indicate whether the following statements are True (T) or False (F):
    1. Oviparous animals give birth to young ones. ( )
    2. Each sperm is a single cell. ( )
    3. External fertilization takes place in frog. ( )
    4. A new human individual develops from a cell called gamete. ( )
    5. Egg laid after fertilization is made up of a single cell. ( )
    6. Amoeba reproduces by budding. ( )
    7. Fertilization is necessary even in asexual reproduction. ( )
    8. Binary fission is a method of asexual reproduction. ( )
    9. A zygote is formed as a result of fertilization. ( )
    10. An embryo is made up of a single cell. ( ) ( )
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  • Answer .
    1. Oviparous animals give birth to young ones. (False )
    2. Each sperm is a single cell. ( True)
    3. External fertilization takes place in frog. (True )
    4. A new human individual develops from a cell called gamete. (False )
    5. Egg laid after fertilization is made up of a single cell. (True )
    6. Amoeba reproduces by budding. (False )
    7. Fertilization is necessary even in asexual reproduction. (False )
    8. Binary fission is a method of asexual reproduction. (True )
    9. A zygote is formed as a result of fertilization. (True )
    10. An embryo is made up of a single cell. (False )
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  • Question 5. Give two difference between a zygote and a foetus.
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  • Answer .
    No.zygoteFoetus
    1.The stage of fertilization, in which fusion of ovum and sperm take place, is called a zygoteThe stage of the embryo in which all the body parts are identifiable is called foetus.
    2. Zygote is a a single nucleus cell and is the first step in the process of reproduction.The Foetus is fully grown embryo with well formed parts and is almost the last step in the process of reproduction
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  • Question 6. Define asexual reproduction. Describe two methods of asexual reproduction in animals.
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  • Answer . Asexual Reproduction : The type of reproduction in which only a single parent is involved is called asexual reproduction.
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  • Two methods of asexual reproduction
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  • Budding :The type of asexual reproduction in which new individuals develop from the buds, is called budding.In hydra, new individuals develop from buds.
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  • Binary Fission : The type of asexual reproduction in which an animal reproduces by dividing into two individuals is called binary fission. Amoeba reproduces by dividing itself into two.
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  • Question 7. In which female reproductive organ does the embryo get embedded?
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  • Answer . In the female reproductive parts, the embryo gets embedded in the wall of the uterus for further development, where it continues to develop in the uterus, finally to form a foetus
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  • Question 8. What is metamorphosis? Give examples.
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  • Answer . The transformation of the larva into an adult through drastic changes is called metamorphosis.For example tadpoles or caterpillars in early stages differ a lot in features than their adult stage later in the form of frog and moth
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  • Question 9. Differentiate between internal fertilization and external fertilization.
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  • Answer .
    Difference between Internal Fertilization and External Fertilization
    Internal FertilizationExternal Fertilization
    Fertilization that takes place inside the female body is called internal fertilization. This is observed in human beings and other animals such as hens, cows and dogs.Fertilization that takes place outside the female body is called external fertilization. This is observed in frogs, fish, starfish, etc.
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  • Question 10. Complete the cross-word puzzle using the hints given below
    1. Across
      1. 1. The process of the fusion of the gametes.
      2. 6. The type of fertilization in hen.
      3. 7. The term used for bulges observed on the sides of the body of Hydra.
      4. 8. Eggs are produced here.
    2. Down
      1. 2. Sperms are produced in these male reproductive organs.
      2. 3. Another term for the fertilized egg.
      3. 4. These animals lay eggs.
      4. 5. A type of fission in amoeba

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  • Solution :
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