DARWIN DAY- FEBRUARY 12

    The father of evolutionary biology, Darwin's contribution to science is significant. Darwin Day is celebrated on February 12 every year. Darwin Day not only  remember his contribution to scientific thought but also to emphasis the importance of science in general.
    Survival of the fittest, struggle for existence, and natural selection these catchphrase come to mind when we think of Darwin. Charles Robert Darwin was  one of the most significant individuals in the history of science ad is considered as the father of evolutionary biology. He published these revolutionary theories in his book' The origin  of species in 1859.
     He developed his theory of evolution by  natural selection through his four observations.His first observation was that all organisms are capable pf producing more offspring than are needed to replace their parents. For example frogs produce hundreds of eggs but all of them do not fertilize. Also, a single tree produces thousands of seeds and all of them do not grow.
   Darwin's second observation was that the population of several different species of animals and plants have a tendency to stay fairly constant over long periods of time. For example, herds of many animals live on the plains of Africa such as Wildebeest, Zebra, Gazelles ete. Each year many of the females give birth, but the over all population sizes of these species stays the same. Competition for food, predation and disease are some of the factors which keep the population size stable
     His third observation was that all living things slightly in colour ,shape, size or behaviour. For example Malabar Giant squirrel which occurs in southern western Ghats, India, has a dark body coat, whereas,in nothern western Ghats and Easter Ghats it is slightly paler with white tail tip. Similarly, a group of frogs from the genus philautus occurs in the western Ghats and shows quite a lot of variation in their body colour
  
darwin's fourth observation was that many features are passed on from the parent to offspring. Some inherited characteristics are quite easy to see in humans such as eye and hair colour. However, some characteristics,like blood group are not visible to the naked eye.
   Based on these observations, Darwin came to two main conclusions. Every organism on earth is involved in a struggle for survivial and some individuals of species are better adapted than other individuals to their environment. The individuals that are most likely to survive and have a chance to reproduce, hereby,passing on their useful adaptions to the next generation. Those do not survive long enough to breed. these ideas formed the basis of Darwin's theory  of evolution by natural selection.
  Darwin concluded that natural selection could explain how organisms gradually change and evolve into new species. When Darwin published his theory,he found it difficult to get it accepted by the scientific community, especially, on how individuals pass their characteristics to the next generation. In the 1930's after the rediscovery of G>H Mendel's pioneering work on genetics, Darwin's theory was broadly accepted. Since then advancement in genetics has provided several evidences to support  Darwin's theory, however ,modern day biologists working on evolution deal more at the gene level and not at the morphological level
( From: P.Jeganathan'sarticle)

Prof. John Kurakar