What is evolution?

We have now learnt about genetics and also realized that evolution is true, but what is evolution exactly? Well,

EVOLUTION IS THE CHANGE IN FREQUENCY OF ALLELES IN THE GENE POOL OF A POPULATION.

Does this sound a bit too hi-fi? This is a fancy of saying that characteristics change as time passes. Change in this context refers to the change in genetic information i.e. - in genes and alleles. This change results in the rise of new forms over a period of time.

Minor changes are classified under microevolution and large changes like rise and extinction of species come under macroevolution. It is believed that lots of small changes lead to a bigger change.

Hey! Wait a minute! What exactly are species? This is a point that needs to be clarified.

A biological species is defined as a group of natural populations that mate and produce offspring with one another, but do not breed with other populations.

If a pig breeds with a duck, the pig or the duck can neither be called species. The word species is widely used, so it is important to know its meaning.

But before that read a bit about Darwin's ideas.This sums up his principles-

1) Organisms evolve. This was not an original idea for him - others had it before, but Darwin restated it.

2) Evolution occurs by natural selection - those individuals, which are most fit (through greater fertility or lesser mortality), contribute more to the next generation. Natural selection is now known to be just one of several mechanisms which produce evolution. It is still thought to be the most important mechanism for evolution by most people and is the only mechanism, which can produce environmentally adaptive change.

3) Natural selection works on individuals. Individuals survive or die and reproduce or fail to reproduce. This is still the most widely accepted idea today

4) Evolution works on a population. A population changes when viewed as a whole. Individuals don't change their genes over the course of their lifetimes.

5) Evolution works gradually. The change from one species to another occurs gradually as small changes accumulate in a population. This is probably a true idea for population genetics (microevolution). However, it is not true for most transitions between species, especially as seen in the fossil record.

6) Darwin did propose a mechanism of inheritance of genetic information. It was incorrect, and Mendel made the discovery of the principles of inheritance later.

The synthetic evolution theory combines the best of Darwin and Mendel and explains evolution in the best way.