Types and Factors of Variation

Variations in pairs of identical twins

There are differences in phenotype if observed, even if from the same ovum

Variation of the butterfly species Biston betularia

Dark-coloured butterflies survives better than light-coloured butterflies during the pollution caused by the industrial revolution

The importance of variation to the survival of Biston betularia butterfly species

Darker butterflies can survive better because they are not easily seen by birds of prey during pollution in the environment

Type of variation

Continuous variation and discontinuous variation

Continuous variation

Variation in which the differences in the characteristics is not distinct

Example of continuous variation

Height, body, weight and skin colour

Discontinuous variation

Variations that show distinct differences in characteristics

Example of discontinuous variation

Ability to roll tongue, eye colour and fingerprint pattern

Continuous variation is quantitative

Can be measured and graded from one extreme to the other extreme

Discontinuous variation is qualitative

Cannot be measured or graded because characteristics can only be determined by genetic factor