How does Evolution and Natural selection work?

One of the first people to pose the idea of evolution were Jean Lamarck and ,the more well known, Charles Darwin. His basic idea was that all animals descended from common ancestors. He also found that nature creates far more offspring that can survive so competition is naturally very high. As a result only the most fit are the ones that survive. Over many generations, this would make animals change to better suit their particular environment. This very early theory of evolution helped scientists come up with the theory that we evolved from apes. However let's look at this ,seemingly simple, theory in practise.

Before the industrial revolution in London, the peppered moth was mostly found in one variety;pale with dark "peppered" spots. This meant that they were easily camouflaged in the light-coloured lichens and tree bark. There was also a less common variety of peppered moth that was completely black, this

source: http://www.evidenceunseen.com

black variety was easily detected by the predators (like birds) that hunted them compared to the lighter coloured peppered moth. This meant that the numbers of black peppered moths were very low because many were eaten before they could reproduce whereas the lighter moths thrived because they were able to live long enough to reproduce and increase their numbers. However when the industrial revolution occurred the light coloured lichens on the trees were killed by  sulphur dioxide emissions, and the trees became covered with soot. This meant that lighter coloured moths were easily detected by the predators, driving their numbers down rapidly. The black moths were able to live long enough to reproduce and increase their numbers rapidly. This meant that black moths had the advantage over the lighter moths. After many generations blacks moths were more common that lighter moths. This is an example of evolution.

Source: http://ayay.co.uk

Different right? The common belief about evolution is that animals change themselves to better suit their environment. However they are being changed, the external factors like predators and the climates change them.For example if a predator becomes quicker it will catch all the prey that is slowest. This only leaves the fastest prey behind who then producing offspring with the same ability.Thus creating a more adapted new generation of the species. 

As always, Seemal