Evolution - Evidences Of Evolution | NCERT concept | Neet Concept | Biology

Evolution - Evidences Of Evolutions| NCERT concept | Neet Concept | Biology

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EVIDENCES OF EVOLUTION

• Evolution is gradual change in the characteristics of a species over several generations and relies on process of natural selection .
• Homologous organs have the same fundamental structures but are different in functions . Thus , homology between organs of different animals is based on common ancestry or common embryonic origin and built on the same fundamental pattern but in adult conditions they get modified to perform different functions . E.g. , the forelimbs of a man , cheetah whale and bat perform different functions but exhibit same structural plan of bones .
• The homologous structures are a result of divergent evolution . Homology indicates common ancestry .
• Analogous organs have similar functions but are different in their structural details and origin . E.g. , wings of a butterfly , bird and bat serve the same function but their basic structures are totally different .
• The analogous structures are a result of convergent evolution .
• Homology in the embryos of closely related vertebrates , indicates their evolutionary relationship .
• Recapitulation theory or Biogenetic Law is based on this evolutionary relationship which states that " Ontogeny repeats phylogeny " . This means an organism repeats its ancestral history during its development . E.g. , in development of frog a fish - like tailed larva ( tadpole ) is formed , which swims and respires by gills . It indicates that the frog has evolved from a fish - like ancestor .
• Vestigial organs are organs present in reduced form and non - functional . E.g. , nictitating membrane , vermiform appendix , hair on body , etc.
• Some organisms possess characters of two different groups of organisms , hence are called connecting links . Some examples of connecting links are as follows

Connecting links        Group of organisms

Euglena                          Between plants and animals

Peripatus                       Between annelida and arthropoda

Balanoglossus              Between non - chordates and chordates

Chimaera                      Between cartilaginous fishes and bony fishes

• Atavism , the reappearance of certain ancestral characters which either disappeared or reduced , is another important evidence of evolution . E.g. , short tail in some human babies , winged petiole in Citrus , etc.
• Different aspects of biochemical affinity like , metabolic processes , enzymes , hormones , blood and lymph , blood proteins and molecular homology are the most convincing evidences of common ancestry .
• Direct evidence of organic evolution comes from the fossils study . Fossils are the petrified remains or impressions of organisms that lived in past and got preserved in the sedimentary rocks .
• The study of past life forms based on fossil records is known as palaeontology .
• The age of fossils is determined by radioactive dating technique . Fossil record can be arranged in chronological sequence once their age is determined .
• Geological time scale is prepared in chronological order based on fossil studies to illustrate the history of evolution .
• Fossil evidences which show combined features of two groups are called missing links . E.g. , Archaeopteryx displays the characters of both reptiles and birds .

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MANISH MEVADA

M.Sc, M.Phil, B.Ed

GUJARAT BIOLOGY NEET

NEET MATERIAL IN GUJARATI 

KNOWLEDGE ON THE WAY.