What are some examples of directional selection?
The example of directional selection is Industrial Melanism ,Darwin finches.
Natural selection has three effects from which directional selection is one .The other two are Stabilisation selection and Disruption selection.
It is one of the factors that affect Hardy-Weinberg Principle.
In directional selection larger no. of individuals acquire value other than mean character value, so peap of graph shifts in one direction.
Example - Industrial Melanism.
What is Industrial Melanism ?
- In England, before industrialisation, white-winged moth were more in no. than dark-winged moths.
- But after industrialization, dark-winged moths became more in no. than white winged moths.
- This is bcz during industrialization, the tree trunks covered by white lichen became dark due to deposition of coal & dust particles.
- As a result, white-winged moths can be easily picked up by predators from the dark background & dark-winged moths survived.
The graph below is showing directional selection with Industrial Melanism.