Mechanism of evolution: Part-1

What is evolution:

Evolution is the development of life on earth, this is a process that started billions of years ago and is still continuing. Evolution tells us how it was possible for the epormous diversity of life to develop it shows us how primitive Protozoa could become the millions of different species that we see today. Evolution, then, is the answer to the question that we all have asked on seeing a Daschund and a Great Dane(Dog species) together. How is it possile for ancestors to have descendants that look so very different to them?
In answering this question, we want to focus on animals, excluding other forms of life such as fungi and plants. The first question to ask is therefore: how can one animal develop into a whole new species of animal?

But a quick question what exactly is a species?

A species is a community of animals that is capable of producing offspring with one another, with those offspring capable of reprocducing in turn.

To have a better answer lets take a closer look at the following points:
the uniqueness of living creatures, guranteed through the excess production of offspring and heredity
and as a second key point, selection.
Lets begin with uniqueness, every creature that exists is unique, and this is essential for evolution.
The members of species may strongly resemble each other in appearence;however they all different traits and characteristics which may vary from being bigger, fatter, stronger or bolder than there fellow animals. So, what is the reason for these differences?

Every creature is made up of cells. These cells have  a nucleus. The nucleus contains the chromosomes. The chromosomes consits of DNA and the DNA consist of different genes, and it's these genes that are life's information carriers.They contain instructions and orders for the cells, and determine the charactersitics and traits that living creatures have, and it's pecisley this DNA that is unique in every creature. It's slightly different from indivisual to indivisual, which is why each has slightly different characteristics.

But how is enormous range of DNA created?

One key factor is the excess production of offspring.In nature we can observe that creatures produce far more offspring than is necessary for the survival of their species, with many offspring dying an early death as a result. Often there are even more offspring than the enviornment they live is able to support.This is one factor in increasing diversity within a species.
They more offsprings they produce the more differences occur and this is what nature wants; as many little differences as possible.The second major cause of the uniqueness of indivisuals occur in heredity itself.

By the way, heredity means the passing on of DNA to offspring. Two very interesting factors come into play in this process: recombination and mutation. Recombination is the random mixing of the DNA of two creatures.

When two creatures fall in love and mate, they recombine their genes twice. The first time, they do this seperatley when they generate the gametes-that is, sperm and egg cells.The gametes take half of the gens and shuffle them.The second recombination occurs when a male inseminates a female.
The parents each provide 50% of their DNA, in other words, 50% of their unique traits and characteristics.These are then recombined and mixed and the result is new offspring. These offspring have a random mix of the DNA, and therefore the trais and characteristics of their parents. This increases the diversity and differences within a species even further, but mutation are also important for evolution.

Mutations are random changes in DNA. These can be described as copying errors within the DNA, triggered by toxins or other chemical substances, or by radiation. A mutation exists when part of the DNA is altered. These changes are often negative, and may result in illness such as cancer.However, they may also have neutral or positive effects, such as the blue eye color in humans, which is one such random mutation. In all cases, a mutation has to affect a gamate, that is a sperm or egg cell, because only the DNA in the gametes is passed on the offspring. This is also the reason why we protect our sexual organs during x-rays, whilst other parts of the body are not at risk. In summary then, in the heredity process, creatures pass on thier characteristics to their offspring in the form of DNA.

Recombination and muation change the DNA so that each child looks different to its siblings, and receives a random mix of the charactersitics of its parents. There is a key word here: Random. All these processes are based on chance. Random recombination and mutations result in indivisual with random mixes of traits and characteristics, which in turn mix these randomly, and pass them on.

But how can so much be down to chance, when all living creatures are so perfectly adapted to their enviornment we will find out in the next part of Mechnaism of Evolution.