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Question
The examples of which of the following include founder and bottleneck effect.
The examples of which of the following include founder and bottleneck effect.
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Solution
The correct option is C Genetic drift
A. Stabilizing selection occurs when the environment does not change. Natural selection has to produce change and if an environment does not change there is no pressure for well adapted species to change. Fossil evidences suggest that many species remain unchanged for long periods of geological time.B. Directional selection occurs whenever the environment changes in a particular way and therefore, is a selective pressure for species to change in response to the environmental change. For example industrial melanism. Industrial melanism is a phenomenon shown by light coloured peppered moth (Biston betularia typica) and dark coloured moth (Biston betularia carbonaria). It is a evolutionary process in which darker individuals predominate over lighter individuals since the industrial revolution is a result of natural selection. Within last 100 years, darkened forms of about 80 species of moths have appeared in varying frequencies throughout the United Kingdom.C. Disruptive selection occurs where an environmental change may produce selection pressure that favours two extreme characteristics. For example, grass plant on welsh copper mines. Contaminated soil containing copper is lethal to normal grass plants but a chance mutation allowed one plant to grow. This plant prospered and reproduced but only on the contaminated soil. On normal soil, it grew more slowly than normal plants and was easily out competed.D. Genetic drift is a random change in allele frequencies over the generation. In small populations frequencies of particular alleles may change drastically by chance alone. Such changes occur randomly as if frequencies were drifting and thus, are known as genetic drift. There are two cases of genetic drift:1. Founder effect- Sometimes, one or a few individuals disperse and become the founder of a new, isolated population at some distance from their place of origin. These pioneers are not likely to have all the alleles present in the source population. Thus, some alleles may be lost from the new population and others may change drastically in frequency. This is called the founder effect.2. Bottleneck effect- Even if organisms do not move from place to place, yet occasionally their populations may be drastically reduced in size. This may occur due to flooding, drought or any other change in environment. The few surviving individuals may constitute a random genetic sample of the original population. This resultant alterations and loss of genetic variability is called bottleneck effect.E. Convergent evolution is a process during which organisms with different evolutionary history evolve similar phenotypic adaptations in response to common environmental conditions.So, the correct answer is Genetic drift.
A. Stabilizing selection occurs when the environment does not change. Natural selection has to produce change and if an environment does not change there is no pressure for well adapted species to change. Fossil evidences suggest that many species remain unchanged for long periods of geological time.
B. Directional selection occurs whenever the environment changes in a particular way and therefore, is a selective pressure for species to change in response to the environmental change. For example industrial melanism. Industrial melanism is a phenomenon shown by light coloured peppered moth (Biston betularia typica) and dark coloured moth (Biston betularia carbonaria). It is a evolutionary process in which darker individuals predominate over lighter individuals since the industrial revolution is a result of natural selection. Within last 100 years, darkened forms of about 80 species of moths have appeared in varying frequencies throughout the United Kingdom.
C. Disruptive selection occurs where an environmental change may produce selection pressure that favours two extreme characteristics. For example, grass plant on welsh copper mines. Contaminated soil containing copper is lethal to normal grass plants but a chance mutation allowed one plant to grow. This plant prospered and reproduced but only on the contaminated soil. On normal soil, it grew more slowly than normal plants and was easily out competed.
D. Genetic drift is a random change in allele frequencies over the generation. In small populations frequencies of particular alleles may change drastically by chance alone. Such changes occur randomly as if frequencies were drifting and thus, are known as genetic drift. There are two cases of genetic drift:
1. Founder effect- Sometimes, one or a few individuals disperse and become the founder of a new, isolated population at some distance from their place of origin. These pioneers are not likely to have all the alleles present in the source population. Thus, some alleles may be lost from the new population and others may change drastically in frequency. This is called the founder effect.
2. Bottleneck effect- Even if organisms do not move from place to place, yet occasionally their populations may be drastically reduced in size. This may occur due to flooding, drought or any other change in environment. The few surviving individuals may constitute a random genetic sample of the original population. This resultant alterations and loss of genetic variability is called bottleneck effect.
E. Convergent evolution is a process during which organisms with different evolutionary history evolve similar phenotypic adaptations in response to common environmental conditions.
So, the correct answer is Genetic drift.
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