Question

Distinguish between directional, stabilizing and disruptive selection.

Answer 1

	Directional selection	Stabilizing selection	Disruptive selection
1.	Directed selection is the process of natural selection acting in a straight path.	innate selection Stabilising selection is the process of working to maintain population balance or stability.	Disruptive selection refers to natural selection that alters the mean characteristics of a population.
2.	In directional selection, more individuals acquire characteristics other than the mean character value.	More individuals in a group acquire a mean character value when selection is stabilised.	More people obtain extreme or peripheral character value in disruptive selection.
3.	Directional selection removes one of the phenotypic extremes and favours the other.	Stabilising selection favours intermediate forms and eliminates both phenotypic extremes.	Disruptive selection encourages extreme phenotypes while removing intermediates.
4.	It streamlines variations	It reduces variations	It increases variations.
5.	This is the most common type of selection.	This kind of selection is common.	This kind of selection is rare
6.	Many generations of directional selection work to move a peak in one direction and create an evolutionary trend within a population.	This selection causes evolutionary change while maintaining phenotypic stability among populations.	It ensures the effect on a population's whole gene pool, taking into account all mating types or systems.
7.	e.g. Industrial melanism, DDT resistance in mosquito, etc.	e.g. All the populations which have adapted to their environment	e.g. African seed cracker finches with different sized beaks