Read the following statements and select the correct option
I. When certain individuals migrate out of the population, gene frequencies change in the population.
II. Stabilising, directional and disruptive selection are types of artificial selection
III. Extreme phenotypes are favoured in the disruptive selection
IV. Single step large mutation is called genetic drift

The correct option is C I and III are correct
When certain individuals migrate out of the population, it may decrease the gene frequency of that particular population. If the population is small, then there are chances for the loss of alleles for a particular trait in that population. Hence, when certain individuals migrate out of the population, gene frequencies change in the population.


Stabilising, directional and disruptive selection are types of natural selection. Natural selection is a process in which individuals which are physically, physiologically and behaviourally better adapted to a particular environment survive, reproduce and leave a greater number of progeny. The rest of those who couldn’t cope with the changing environments will perish.

Stabilising selection acts to eliminate extreme phenotypes and favour individuals with intermediate phenotypes.

Directional selection favours individuals exhibiting one of the extreme phenotypes, thereby shifting the curve for the phenotypic character in that direction.

In disruptive selection, individuals with the extreme values of the trait are favoured and individuals with the mean value of the trait are eliminated.

Artificial selection is a man-made selection. It is the identification of the desirable traits in organisms by human beings, and the steps taken to enhance and perpetuate those traits in future generations. Artificial selection by humans has resulted in the creation of various high yielding breeds in plants and animals.

Single step large mutation is called saltation and it leads to the formation of new species according to Hugo de Vries.

Random changes in the gene frequency by chance is called genetic drift.

Hence, statements I and III are correct.