Origin of Life
The first scientific account of the origin of life was given by Russian scientist AI Oparin in his book 'Origin of Life'.
The primitive atmosphere contained hydrogen,Methane,Ammonia and water vapour.In it Oxygen and Ozone were absent.Thus it was believe that life is originated from inorganic substances by a series of complex reaction.This is also supported by Miller and Urey in 1953.
Organic Evolution
More and more creation of organism by gradual changes from low categories animal to higher animal is called organic evolution.These are several evidence regarding organic evolution.
Homologous Organs
The organs which similar in basic and origin but similar or dissimilar in functions are called Homologous organs,e.g.,wings of bat,cats paw,front foot of horse,humans hand and wings of birds are homologous organs.
Analogous Organs
These are developed in organism widely different phylogenetically due to similar habitats and moodes of life,e.g., wings of insects,birds and bats ,eyes of octopus and mammals are analogous organs.
Vestigial Organs
These are degenerate,non-functional organs which were functional earlier.
Human body has been discribed to possess about 90 vestigial organs.Some of these are muscles,eat pinna,canine,teeth and third molar teeth,body hairs,membrane of eyes,caudal vertebral etc.
Evidence from Connecting Links
Connecting link is one which exhibit characteristic of more than one groups.
Intermediate Forms between Two Groups of Organisms.
| Organism | Connecting Link Between |
|---|---|
| Virus | Living and non-living |
| Euglena(protozoa) | Non-chordata and Chordata |
| Dipnoi(lung fish) | Pisces and Amphibia |
| Archaeopteryx | Reptiles and Aves |
| Balanoglossus | Plants and Animal |
| Prototheria | Reptiles and Mammal |
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