LAMARCKISMAND NEO LAMARCKISMv Jean-Baptiste Lamarck is aFrench Naturalist who lived during the period of 1744-1829. Lamarck haspublished books in the field of InvertebrateZoology and Paleontology. Thepopular book called Système des animaux sans vertèbres waswritten by Lamarck.
v Lamarckism is the theory of organic Evolutionproposed by Lamarck. It explains about the origin of new species. It is alsoknown as theory of inheritance of acquiredcharacteristics.v Lamarckism consists of four postulates. They are Ø Law of inherent capacity – Animals and plants has theability to grow and increase in Size to attain a maximum growth. According toLamarck, this tendency of the organisms is due to the internal urge in them toincrease in sizeØ Environment and new need-organismdevelop new characters based on the Environmental and their own need.
Ø Use and disuse Theory-If aparticular part or organ is used or not used for a long time it will result inincrease or decrease in size of thatorgan. Example is neck of Giraffe.Ø Inheritance of acquired characters-The transmission of characters developed by the organism during its lifetime. Example loss of eyes in cave dwelling organisms.v The first two theories of Lamarck were accepted but objections arose to the other two theories ofacquired characters because he didn’t distinguish heritable from non-heritable charactersand explained only the importance of the character or the change not its origin and mechanismof transmission.v An example for objection to third law was noincrease in size of blood vesselsthough they were used continuously.v An example for objection to fourth law was no pierced ears wereseen in newly born babies who parents have pierced ears. It was officiallydisproved by August Weismann by proposing GermplasmTheory.
v As a result of these discrepancies, Neo Lamarckism wasproposed. It is a modern version of Lamarckism. Many scientists havecontributed for the development of Neo Lamarckism. v George Henslow 1835–1925 wanted to studythe Evolution of plants based on the effect of environmental stress on growthof plants.v Edward Drinker Cope and Alpheus Hyatt studiedfossils to see the evolutionary trends.v Samuel Butler thoughtthat the evolution of the organism is shaped by the Inheritance of acquired characters.v Theodor Eimer combined the Lamarckismconcept with orthogenesis.v Ernst Haeckel supported the concept of Lamarckism.Thus Lamarckism and Neo Lamarckism have contributed a lot to study theEvolution.