Question

Describe a specific example where natural selection is likely to have produced a specific trait, feature or behaviour. In your example make sure you use the 3 principles of natural selection which are principle of variation, principle of inheritance, and principle of adoption.

Answer 1

The principle of natural selection include variation, princilple of inheritence and principle of adoption (selection).

Principle of Variation - Considering a population, organisms within the population show differences in some characters whereas some traits show no variation. These differing factors body size,colour etc. Number of fingers in hand, number of legs or eyes generally show no variation.

Principle of inheritence- Some traits are heritable while others show weak heritability

Principle of adoption or selection- The traits which enhance survival of the individual in its habitat will be selected by nature and transfered into the next generation.

Example- Natural selection of melanic moth duing industrial revolution

Peppered moth, Biston betularia population consist of majority of individuals with light coloured wing (peppered). This colour is suitable for the moth to be camouflaged in bark of lichen covered tree trunks. There is also rarely found peppered moths with black coloured wings (melanic forms). Here the principel of variation is shown. That is there is differences in phenotypic characters among the moths considering wing colour.

Principle of inheritence and adoption-

Before industrial revolution, the number of peppered moths were larger than the melanic moths. Because melanic moths are easily visible to the predators. Compared to light coloured winged moths sitting in lichen covered tree trunk , black moth sitting in light coloured tree trunks are ofcourse conspicous to predators. Therefore the gene for light coloured wing inherited mostly. (Principle of inheritence).

After industrial revolution (19th century), the region (Britan , Ireland) the black moth outnumbered. It was because due to the coal burning the city was polluted and lichens were completely wiped out. The tree trunks and walls were blackened. Now the environmental condition favoured the black moth for easy camouflage than pale coloured moth. The gene for black coloured wing were selected and inherited through the succesive generations. The selection of character which is adapted better was done by nature.

The story continued till 20th century, when measures were taken to minimize pollution, the lichens reappeared covering the tree trunk which turned to light colour. Subsequently pale coloured moth ioutnumbered black moth again due to selection of character that can adapt better.