Prof. Dr. Sohan Raj Tater
Theory of evolution is related to the science of genetics. Theory in biology postulating that the various types of the animals and plants have their origin in other pre-existing types are that the distinguishable differences are due to modifications in successive generations. The theory of evolution is one of the fundamental keystones of modern biological theory.
The 19th century English naturalist Charles Darwin argued that organisms come about by evolution and he proved a scientific explanation, essentially correct but incomplete, of how evolution occurs and why it is that organisms have features—such as wings, eyes and kidneys—clearly structured to serve specific functions. Natural selection was the fundamental concept in his explanation. Genetics, a science born in the 20th century, reveals in detail how natural selection works and led to the development of the modern theory of evolution. Since the 1960s a related scientific discipline, molecular biology, has advanced enormously knowledge of biological evolution and has made it possible to investigate detailed problems that seemed completely out of reach a few years earlier, for example, how similar the genes of humans and chimpanzees might be (they differ in about for 2% of the units that make up the genes).
The virtually infinite variations on life are the fruit of the evolutionary process. All living creatures are related by descent from common ancestors, humans and other mammals are descended from shrew like creatures that lived more than 150 lac years ago is mammals, birds, reptiles, amphibians and fishes share as ancestors aquatic worms that lived 600 lacs years ago, all plants and animals are derived from bacteria like micro organism that originated more than 3000 lacs years ago. Biological evolution is a process of descent with modifications. Lineages of organisms change through generations, diversity arises because the fine ages that descent from common ancestors diverge through time. [103]
The diversity of the living world is staggering. More than 2 lac existing species of plants and animals have been named and described, many more remain to be discovered from 10 lacs to 30 lacs according to some estimates. What is impressive is not just the numbers but also the incredible heterogeneity in size, shape and way of life from lowly bacteria, measuring less than 1000th of a millimeter in diameter, to the stately squoias of California, rising 300 ft (100 meters) above the ground and weighing several thousand tons, from bacteria living in the host springs of Yellow Stone national park at temperatures near the boiling point of water to fungi and algae thirving on the ice masses of Antarctica and in saline pools at 90f (-230c) and from the strange and larkspur plants existing on Mount Everest more than 19868 feet above sea level. (Britanica Encyclopaedia 2005, deluxe edition).
Doctoral Thesis, JVBU