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Question
Read the following assertion and reason statements and choose the correct option.
Assertion: Evolution in Escherichia coli can occur in few days
Reason: The rate of evolution depends on the life-span of an organism
Read the following assertion and reason statements and choose the correct option.
Assertion: Evolution in Escherichia coli can occur in few days
Reason: The rate of evolution depends on the life-span of an organism
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Solution
The correct option is B Both assertion and reason are true and the reason is the correct explanation of the assertion
Evolution is the change in heritable traits of biological populations over successive generations giving rise to diversity. The concept of evolution is based on the idea that all species are related and have descended from a common ancestor progressively over time.
Escherichia coli has a very short generation time,i.e, a single bacteria undergoes rapid cell division every 20 minutes and will develop a progeny of millions within hours.
For example, a bacterial colony (say A) growing on a particular medium has built-in variation in terms of ability to utilise a feed component. A change in the composition of the medium would bring out only that part of the bacterial colony (say B) that can survive under the new conditions. This variant population (B) multiplies rapidly and appears as a new species within a few days. This is because the organisms with shorter life spans have a shorter generation time and reproduce rapidly. Thus, inheritable changes or variations in their genetic constitution, gets rapidly transferred to the progeny. Whereas, those with longer life spans have a longer generation time and it takes longer time to pass on the variations to their offspring. Thus, accumulation of useful variations leading to evolution of a new species takes millions of years.
Hence, the rate of appearance of a new form or variant due to evolution is related to the life-span of an organism. The shorter the life-span of an organism, the faster the rate of evolution in them.
Evolution is the change in heritable traits of biological populations over successive generations giving rise to diversity. The concept of evolution is based on the idea that all species are related and have descended from a common ancestor progressively over time.
Escherichia coli has a very short generation time,i.e, a single bacteria undergoes rapid cell division every 20 minutes and will develop a progeny of millions within hours.
For example, a bacterial colony (say A) growing on a particular medium has built-in variation in terms of ability to utilise a feed component. A change in the composition of the medium would bring out only that part of the bacterial colony (say B) that can survive under the new conditions. This variant population (B) multiplies rapidly and appears as a new species within a few days. This is because the organisms with shorter life spans have a shorter generation time and reproduce rapidly. Thus, inheritable changes or variations in their genetic constitution, gets rapidly transferred to the progeny. Whereas, those with longer life spans have a longer generation time and it takes longer time to pass on the variations to their offspring. Thus, accumulation of useful variations leading to evolution of a new species takes millions of years.
Hence, the rate of appearance of a new form or variant due to evolution is related to the life-span of an organism. The shorter the life-span of an organism, the faster the rate of evolution in them.
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