Reproduction in Animals NCERT Science Class 8 Chapter 9 Summary Note


Reproduction in Animals
·         
     Reproduction (Re+Production)
Production of living being of own kind, is called reproduction.
·        
     Importance of reproduction
Reproduction ensures continuation of similar kinds of individuals, generation after generation.
·        
     Modes of reproduction
(a) Asexual  reproduction
(b) Sexual reproduction
·     
         Sexual reproductio
      Mode of reproduction where
              -Two parents are involved.
              -Formation of gametes takes place.
             -Fusion of male and female gamete takes place,
       Is called sexual reproduction.
·        
       Asexual reproduction
 Mode of reproduction where
              -Single parent is involved.
              -Formation of gametes do not takes place.
              -Fusion of male and female gamete do not takes place,
          Is called asexual reproduction.
·       
            Male reproductive organs-
It consists of – a pair of testes
                          Two sperm ducts
                         A penis
·      
            Testes produces millions of sperms.
·     
             Sperm- Male gamete
            -Very small in size.
            -Each sperm is a single cell.
          - Each has a head, a middle piece and a tail.
·      
              Female reproductive organs
             It consists of – a pair of ovaries
                                    -A pair of oviducts/fallopian tubes
                                    - a uterus
·         
          Ovary produces single mature egg every months.
·         
          Egg/ova- Female gamete
                  -Each egg is a single cell.
·     
               Uterus-
    Part where development of baby takes place, is called uterus.
·       
               Fertilisation
   The process of fusion of male and female gamete to form zygote is called fertilization.
    Sperm(male gamete) + Egg(female gamete) --à Zygote
    it takes place in oviduct.
·       
                Zygote is the beginning of new individual.
·        
          Types of fertilization
    (a) External fertilization
    (b) Internal fertilization
·        
           External fertilization
     Fusion of male and female gametes takes place outside female body.
      More number of eggs are produced.
      It takes place in aquatic animals.
     Zygote survival chance – less.
·       
                Internal fertilization
    Fusion of male and female gametes take place inside female body.
    Only one egg per month is produced.
   It takes place in terrestrial animals.
    Zygote survival chance – more.
·         
         Zygote -à Embryo à Foetus à Baby.
·     
               Embryo- Zygote developes into embryo.
·   
               Foetus – Stage of the embryo in which all the body parts can be identified.
·        
        Viviparous-
   The animals which give birth to young ones are called viviparous.
    Example- Human.
·     
               Oviparous
   The animals which lay eggs are called oviparous.
    Example- Hen.
·       
                Metamorphosis
   The transformation of the larva into adult through drastic changes, is called metamorphosis.
    Larva ----à Adult (Metamorphosis)
·         
          Asexual reproduction
    (a)Budding
    (b)Binary fission
·    
                Budding- Development of new individuals from bud or bulge.
·        
         Binary fission – An animal reproduces by dividing into two individuals.
·      
                 Dolly- First cloned mammal.





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