What is Evolution?
Biologically, evolution can be best described as a descent with modification. This definition of evolution encompasses two basic types of modifications, firstly, small scale modification which is the change in gene frequency in a population from one generation to another, and secondly, large scale modification which is the descent of different species from common ancestor over a very huge span of time. Evolution influences every aspect of the form and behavior of organisms.
Evolution can also be defined as a change in the biological function and mechanical response of a species towards its environment which may include associated changes in appearance, metabolism or lifestyle and can be passed from one generation to another.
Evolution drives the diversity on our planet. Every living being on Earth once shared a common ancestor which passed down its legacy over billions of generations to create the amazing ecosystem that exist on our planet today. Over billions of years repetition of the similar species, change within species and loss of species has happened that kept the engine of the food chain running. The strongest of all the species survived and the weaker ones perished.
The evolution on Earth occurs when there are changes induced due to different mechanisms by some long time exposure. These mechanisms are the basic wheels of evolution and have carried the early life from the single cells to multi cellular complex organisms to vertebrates that came out of the oceans and populated the land.
These mechanisms for evolution are:
1. Natural Selection:
Natural selection is a process by which the stronger and efficient genes are passed on to the next generation by the survival of the fittest and perishing of the weak one in the war of food chain. It is called Natural Selection because it happens as per the naturally set food chain which has emerged as a balance among all the organisms living in an ecosystem. The weaker ones die and the strong ones remain to reproduce stronger offspring and hence species evolves throughout over millions of years.
2. Mutation:
Mutation is one of the major sources of evolution. This happens when there are different possibilities for mutations on the molecular level. This can be better explained by considering an example of two genotypes with nucleotides G and other one with A are in the same position and have same fitness, but, mutation from G to A happens more often than from A to G then the genotypes with A will tend to evolve. The evolution due to mutation takes place on a very molecular level and there was nothing which could have been done about them until recently humans learned to understand them.
3. Adaptation:
Adaptation is a process by which an organism adapts a certain habitat and makes them better suited to it. It can be best understood by taking an example of the first organism which came out of seas to live on lands. In the sea they were protected from the gravity due to the buoyant force of the water but on the land they were on their own to fight against the mighty gravitational pull of Earth. This surprisingly new habitat forced the organisms to evolve into vertebrates that had a skeleton system in their body which provided them the strength to make movements in spite of the gravity.
4. Migrations:
This is one mechanism of evolution which happens when one species migrates into some other species and reproduced to create a mixture of both the species. For example there are two types of beetles, brown and green. If suppose one brown beetle migrates into the population of green beetles and mated with one of them, this would create a whole new different species which will be a mixture of the green and brown beetles.
