Read the given passage and answer the questions that follow :-
In a given population one can find out the frequency of occurrence of alleles of a gene or a locus. This frequency is supposed to remain fixed and even remain the same through generations. Hardy-Weinberg principle stated it using algebraic equations. This principle says that allele frequencies in a population are stable and is constant from generation to generation. The gene pool remains a constant. This is called genetic equilibrium.
A small section of a population migrates to a new place. By chance, the allele frequencies in this new sample become so different from the original population that it becomes a different species. What is this effect called?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Founder effect
The allele frequencies of a population can change in more than one way. When a section of a population moves to another place, gene frequencies change in both the old and the new population. If such a change happens by chance, it is genetic drift. Sometimes the new sample becomes so different that it becomes a different species; the drifted population then forms the founders of the new species.
Option (1) Gene flow — Incorrect. Gene flow is the change brought about when gene migration takes place multiple times, adding new alleles to one population and removing them from the other. The case describes one chance change that leads to a new species.
Option (2) Founder effect — Correct. When the original drifted population becomes the founders of a different species, the effect is called the founder effect.
Option (3) Adaptive radiation — Incorrect. Adaptive radiation is the evolution of many different species from a point within one geographical area, radiating into different habitats, as in Darwin’s finches.
Option (4) Saltation — Incorrect. Saltation is the idea of de Vries that a single step large mutation causes speciation. The case involves a chance change in allele frequencies, not a mutation.
NCERT Extract:
Hardy-Weinberg Principle – “… When migration of a section of population to another place and population occurs, gene frequencies change in the original as well as in the new population. New genes/alleles are added to the new population and these are lost from the old population. There would be a gene flow if this gene migration, happens multiple times. If the same change occurs by chance, it is called genetic drift. Sometimes the change in allele frequency is so different in the new sample of population that they become a different species. The original drifted population becomes founders and the effect is called founder effect.”