Define external fertilization. Mention its disadvantages? (NCERT)

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Answer :- External fertilization occurs outside the body of the organisms. During this process, the parents release sperms and eggs into surrounding water (example, frog) where fertilization occurs. The major disadvantages of this type of fertilization are: (i) the fertilization of egg is not always sure (ii) the offspring are not protected from the Predators (iii) a large number of gametes are wasted. 

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