Organic Evolution

Organic Evolution:

More and more creation of organisms by gradual changes from low categories animal to higher animal is called  organic evolution .There are several evidence regarding  organic evolution. 

1.Homologous organ: Organ which are some different due to use in its function but internal structure and embryonic development are similar. Ex_ Flipper of whale, feather of bat, forelimb of horse, paw of cat and hands of human.

 2. Analogues organ: Organ which looks similar due to be used in similar function but their internal structure and embryonic development are different. Ex_ Wings of butterfly, bats and birds all looks Similar  but their internal structure and origin are different. 

3. Vestigial organ :  These are organs which appear functional in an organism but was functional in their ancestor. For example Vermiform appendix of large intestine  and nuctitating membrane of human. Vermiform appendix is functional in herbivorous mammal even now.

4.Fossil __ Fossils are the remains of ancient plant or animal which provide evidences for evolution. Example _ Archaeopteryx. 

5. Archaeopteryx: It is a fossils looks like burd but bear a number of features found in reptiles. So, it is a connecting link between waves and reptile.

Theories of Evolution 

1. Carolus Linnaeus (1707_ 1778)   contribution to classification provide an evolutionary relationship among the organism. He was also supported an idea that no species is new. Each and every species originates from some pre_ existing species. 

● He wrote ' species plantarum' and proposed binomial system of nomenclature. 

 2.Jean Beptist Lamarch (1744_ 1829) tried to explain the evolutionary process in his book philosophic zoologiplque.The theory proposed by Lamark  is known as theory of inheritance of acquired characters .According to this theory use and disuse of an organ lead to acquiring change in the features of that organ. These changes are also inherited to offspring. The favourable changes after long period of time result in evolution of new species. But Lamarckism was very strongly criticized by Agust Weismann. 

3. Charles Robert Darwin (1809_ 1882)  explain the evolutionary principle in his book 'The origin of species'.The theory proposed by him is popularly known as ' Theory of natural selection' or Darwinism. Darwin in explained that despite having the enormous potential of fertility, the population of organism remains within a limit.It is due to struggle between members of same species and different species for food ,space and mate. Struggle eliminates the unfit individual. The fit organism possess some variations which are favourable and they can leave the progeny to continue the favourable variation.The  variation when accumulated for long time give rise to origin of new  species with progress in genetics, the sources of variation were explained and Darwin's theory was modified. Now the most excepted theory of evolution is Modern Synthetic Theory, which origin of species is based on the interaction of genetic variation and natural selection. 

● Among Permian, Triassic, Cretaceous and Jurassic geological  era cretaceous is the newest one.

● The book which contains information about all plant is called red data book.

● Recepitulation theory was proposed by  Erunst Haeckel 

● The basic unit of biosystematica is species.

● The correct taxonomic hierarchy is __ Kingdom ➡️ Phylum➡️ Class ➡️Order➡️ Family ➡️Genes ➡️ Species. 


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