Accumulation of Variations


 
 
Concept Explanation
 

Accumulation of Variations

We have different organisms all around us. They all look different as species differ from each other. But when you look for differences among individuals of a species, no two individuals are identical to each other. We acquire a common body design along with subtle changes. Take an example of bacteria.

  • Suppose a bacterium produces two bacteria by asexual reproduction.
  • One of the offspring bacterium has a variation due to which it can tolerate a little more heat resistance.
  • This characteristics of heat resistance will go on accumulating in the offspring of successive generation of this bacterium, and this will ultimately give rise to a variant of bacteria which will be highly heat resistant and able to survive even at very high temperatures.
  • The advantage of variation to a species is that it increases the chance of its survival in a changing environment.
  • There would be only very minor differences between them, generated due to small inaccuracies in DNA copying mechanism, the diversities quite high in case of sexually reproducing organisms because of reshuffling of traits during gamete formation and chance fusion of gametes during fertilisation. If the DNA comes from two parents, the differences will be pronounced. The earlier differences will pass on to the next generation's offspring as well as the new ones they inherit from their parents.

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    Sample Questions
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    Question : 1

    Which of the following are correct ?

    (a) Bacterium produces two bacteria by asexual reproduction.

    (b) Variations in an individual may be an advantage or a disadvantage for the organism.

    (c) The advantage of variation in sexual reproduction is that the variations accumulated in the gametes of each sex are combined when they fuse to form the zygote

    Right Option : D
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    Question : 2

    Which of the following are correct ?

    (a)  The advantage of variation to a species is that it decreases the chance of its survival in a changing environment.

    (b)  As gametes and zygote formation are not involved, the asexually produced offspring are quite similar.

    (c)  Significance of the variation is that they form the basis of heredity .

    Right Option : B
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    Question : 3

    An offspring produced from the zygote receives and carries the variations of ________________________

    Right Option : B
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