The theory of evolution offers an explanation of how the great variety of present day plants and animals came into being. It supposes that life on earth began in relatively simple forms which over hundreds of millions of years gave rise, by a series of small changes, to a succession of living organisms which became more varied and more complex. It must however be emphasized that evolution is a theory and not an established fact. In general terms it is an acceptable hypothesis to account for the existence of the living organisms that we know today.
The arguments for evolution are based on the facts of reproduction, the fossil record and circumstantial evidence. All living organisms that we know are derived from reproduction from pre existing organisms and do not rise spontaneously from non-living matter. This fact weakens any alternative theory to evolution, if it claims that each kind of organism known today arose spontaneously or was created suddenly at different points in time. The evolutionary theory would assume that when new forms of life appear on earth, they have been derived by reproduction from organism that already exist e.g. that mammals were derived from reptiles, reptiles from amphibians and amphibians from fish. In general, for vertebrates at least the fossil record supports this contention.
When we study the fossil records of the past we observe that many day plants and animals are not represented and that a great number of organisms whose fossil records have been found no longer exist today. Such evidence does not support any theory that states that all the organisms existing today have been reproduced exactly since life began.
The limbs of seals, moles, bats and antelopes look very different from each other and are adapted to the function of swimming, digging, flying and running. Despite the difference in appearance and function, they all have basically the same skeletal structure. If these mammals did not evolve from a common ancestor but arose independently and spontaneously there seems no convincing reason why the pattern of bones in limbs performing such different functions should be so similar. On the other hand it is reasonable to visualize these limbs as modifications of the primitive unspecialized limbs of a common ancestor.
Many people think that Charles Darwin proposed the theory of evolution. He didn't. ...
The solution discusses Evolution and Darwin's and Lamarck's theories on evolution.