Lamarck
Jean Bapliste pierre antoine de monet lamarck(1744-1829) was a french naturalist well known for his theories of evolution. In 1778 lamarck published work in "flore francise" in this book he developed dichotomous key that help in the idebtfication of species. In 1809 Lamarck elaborated his Doctnine of evolution in his masterpiece 'Philosophie zoologique' in spite of his impaired sight.Lamarck become blind in his later year and died in great poverty in Paris on December 18,1829 Lamarck name is inseparably linked with the theories of evolution. But he had attributed to biology in a number of other ways. He introduced the word "biology" to emphasize the kinship between living being's (i.e plants and animal). he also provide detailed investigations of fossils and living invertebrates.
Lamarckism ( Theory of inheritance of acquired characters)
This theory was proposed by Lamarck in 1809. It was published in "Philosophie zoologique" in the year 1809. Tt was popularly known as " The inheritance of acquired characters in organisms. Lamarck theory of inheritance of acquired characters can be defined as " The change in structure or funcation of any organ acquired during the life time of an individual in response to change in the surrounding environment are inherited by it,s offspring,s and keep on adding up over a period of time.
Postulates of Lamarck theory
Lamarck theory based on those factors or postulates;
New needs; Change in the environment create new needs in living organism so that those are batter adapted or more suited to the changed environment. the organism have to put new needs. Those efforts lead new need result in the formulations to grow.
Acquisition of new characters;
New characters are acquired by the living being in two ways.
(1)By use and disuse; The new habits involve grater use of certain organ to meet the new need. and disuse or less use of certain other organs in changed conditions. Continue use of an organ keep them functional and makes them stronger, larger and functional and more efficient. Continues disuse of a organ or organs leader to gradual reduction in their size and to their final disappearance.
(2) Effect of environment; Changes in temperature, light, medium, food,etc. influence the functioning and behaviour of living beings and thus organisms acquired certain new characters due to direct or indirect influence of environment.
Inheritance of acquired characters;
The changes acquired by an organism during it,s life time are inherited to the next generation. In every generation some new characters were acquired or the older ones keep on increasing or improving as a result, after a number of generation the species get,s modified into a new one
Evidence in favour of Lamarck theory
Evolution of long neck in giraffe; according to Lamarck had short neck and forelimbs and grazed on grass. As the climate change the area change into a desert. thus leaves of these high tree's was only food avaliable to the ancestor of giraffe. They had to continuously stretching their neck and forelimbs. Result in gradual elongation of neck and forelimbs. The increase was transmitted to the member of next generation
Evolution of snakes; According to Lamarck the ancestor of snakes were limb and lizard. but the ancestor started creeping jungle floor and living in narrow crevices they stretched their body, which were of no use but proved to be a hindrance in creeping and burrowing gradually disappeared
Some other examples;
(a) Eyes are reduced in moles because they lived under ground
(b) Biceps muscles in the right arm of blacksmith are more developed because of the collect sound waves from surrounding
(C) Fight less birds ( kiwi of New zeland ostrich from Africa and emu from Australia) are belived to have descended from flying bird.
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