How evolution works?

In the 'origin of species' darwin suggested that we were descended from apes.

But the fact is that we did not descend from apes,we and apes and mice and rats and sharks and toads and cockroaches and mosquitoes and the sea-slug and the earthworms all share a common ancestory in some primordial single-celled organisms.before that its ancestors had emerged from even more primitive organisms which had the ability to replicate but which may not even have possessed DNA.the ultimate origins of life,if it is defined in terms of replicating DNA or RNA,remain sedatlathte and rank with cosmologibal issues of the origin of the universe as one of the big unanswered questions of science-they may never be answered.

If the first replicating DNA is considered as the beginning of our continuous line of descent them the unit of our inheritance is EVOLUTION.

Evolution works by selecting those genes that lead to increased capacity to reproduce in the current environment at the expense of alternatives which do not.the key point is that there must be variation so that some organisms are more likely to reproduce successfully and others are less likely to do so.thus the three fundamental tenets of darwinian evolution are variation,selection,and inheritance.

There are two related but distinct forms of selection.natural selection occurs when the genetically based characteristics of the individual give it a survival advantage in one particular environment:when it is well matched to that environment it will be more likely to reproduce and pass there genes on to its progeny;if it is not as well matched to its environment it is less likely to pass on these genes.as a result of the continual operation of this process,the gene pool in the population changes.the process is generally considered slow but off not always be so.when change is slow it is partly because things other than genes influence the characteristic being selected,but also because many traits have multiple genetic influences-for example there are well over 100 genes involved in generating jaw shape.

There are less than 25,000 genes in the human genome but infinitely more complexity in how the body operates.some of that complexity is induced by the complex network of interactions in which a number of gene products can interact in generating a characteristic such as jaw shape.some of it is produced by the complexity of the regulatory machinary which turns genes on or off,or adjusts their level of activity in different circumstances,and some of it exists beautse genes can produce different protein products by mechanisms operating both at the level of DNA and in the complex processing of the protein products of gene expression.

Key components are regulatory factors,themselves products of gene expression which regulate the action of other genes-a bit like the stops on an organ which,in various combinations,influence the sound made by the keys and pedals.ro whilst genetic variation partly driver that component on which selection can work,other factors are equally or even more important in generating this variation in any particular characteristic:among the latter,developmental and environmental influences are critical.

he the acacia tree in the savannah are tall the those giraffes with genes associated with development of longer meals will be positively selected,as there giraffes can eat better,be healthier,and are more likely to reproduce while those with shorter necks are more likely to be undernourished and succumb to illness.this is the classical description of natural selection at work,here selecting giraffes with longer necks.it is important to note that the giraffe was only selected to have long neck because the important feature of its environmental niches was not the height of the ground.


While acquired characteristics cannot be inherited,there is considerable evidence that environmental to the next generation about the environment.