Peppered Moths

How they changed due to natural selection

What is Natural selection?

Natural selection is defined as 'The process by which heritable traits that increase an organism’s chances of survival and reproduction are favoured than less beneficial traits. Originally proposed by Charles Darwin, natural selection is the process that results in the evolution of organism'

-Biology Online

What is the Peppered moth? Where does it live?

The peppered moth (Biston betularia) is a temperate species of night-flying moth. They are found in countries such as China, Japan, Russia, South Korea, Europe and North America among others, where they tend to live in woods, gardens and towns.

Scientific Classification

Kingdom: Animalia

Phylum: Arthropoda

Class: Insecta

Order: Lepidoptera

Family: Geometridae

Genus: Biston

Species: B. betularia

What is its significance in evolution and natural selection?

Up until the Industrial Revolution, peppered moths were typically whitish in colour with black spots, although they were found in a variety of shades. When newly industrialised parts of Britain became polluted in the nineteenth century, the lichen growing on the trees and houses died out and so soot turned both the white bark and houses black. This made the light moths unable to camouflage themselves. Birds then began to eat more of the lighter-coloured moths because they were more easily spotted than the darker ones.

When the light moths started to be prey, the dark moths began to reproduce a lot more. This beneficial trait of being darker was then passed onto the next generations of moths making the darker moths more prelevant in the population. This process helped the moth species to evolve in order to increase its chances of survival.

Evolution of The Peppered Moth

Peppered Moth

Effect on the population?

The population of peppered moths prior to the industrial revolution consisted of the most part light peppered moths and only very few darker ones, roughly 2%. As the environment changed and the light moths were now unable to camouflage, the ligh population decreased and the darker moths began to repopulate growing up to around 95% of the population. Since then with change in pollution rates, light-coloured peppered moths have again become common.

Evolution of the Peppered Moth

Why is this all so important?

The dramatic change in the peppered moth's population during the industrial revolution

has been researched and studied extensively thus it has become an expert example used to explain and demonstrate natural selection.