Lamarckism and neolamarkism
- 1. DR SHARMISTHA CHAKRAVARTY DEPT OF ZOOLOGY BARNAGAR COLLEGE SORBHOG, ASSAM
- 5. NEW NEEDS: Changes in environmental factors like light, temperature, food, air or migration leads to origin of new needs in living organisms. To fulfill this, living organisms have to exert special effort like change in habitat or behaviour. USE AND DISUSE OF ORGANS: The new habits include greater use of certain organ to meet the new needs and disuse of certain organs that are not required in the ne environment. INHERITANCE OF ACQUIRED CHARACTERS: He believed that the favorable aquired characters are inheritable and transmitted to the offsprings so that they are born fit to adjust in the new environment.
- 10. Increase in size: Lamarck suggested the tendency to increase in size. Many examples from plant kingdom contradict this postulate by reduction in size during evolution. Internal urge: This postulate is quite false and illogical. Use and disuse: This postulate is not applicable for all. For example eyes constantly in use become inefficient in future. The constant use of heart has also retained in size.
- 12. Inheritance of bony plates in Stickle back: If a fresh water stickle back is taken to sea it gradually develops the bony plates, this is an acquired character and inherited by offspring. And if marine fish is bought to freshater, it loses all the bony plates. Experiments on potato beetle: Experiments of Tower on the potato beetles have demonstrated direct effect of environment on the germ cells, but no change in somatic cells.
- 13. Effect of antiserum: Guyer and Smith demonstrated that substance carried by blood might serve as a link among soma and germ cells thus inducing inheritance of acquired characters. Effect of manganese on moth: Heslop Harrison demonstrated that a pale variety of moth, Selonio bilunaria if fed on manganese coated food, a melanic variety of moth is produced. Experiments on Proteus: Kammerer conducted experiments on Proteus anguineus that lives in total darkness in stream and caves, its eyes are vestigial and its colorless but if bought to daylight it becomes black in color and eyes develops normally.
- 14. • Effect of temperature on mice: Summer reared albino mice at high temperature then the mice developed longer body, longer hind limbs and a long tail. These abnormalities transmitted to the offsprings. • Training experiments on rats: Mc Dougall trained rats to take certain escape routes from a tank and this experiment repeated for many generations, this is inherited. • Inheritance of acquired diseases: Sequard found that several acquired diseases are transmitted from one generation to another.
- 15. Environment is the driving force of evolution. Change in environment brings about changes in the heredity of organisms. Germ cells are influenced by the environmental changes. The germ cells may carry acquired or somatic variations to the offsprings. Germ cells may be affected directly by the environmental factors. Somatic characters are the result of interaction among genes and environment.
- 16. LAMARCKISM NEO LAMARCKISM Theory proposed by Lamarck to explain the phenomenon of evolution. It is a modification of Lamarck’s theory to make it more acceptable. Lamarckism believes in the presence of a internal vital force that leads to changes in organisms. Neo lamarckism does not recognize any internal vital force in organisms Use and disuse of organs is a major factor in evolution It does not give importance to use and disuse Somatic and germ cells distinction is not made It distinguishes germ cells from somatic cells All acquired characters are believed to be inherited Only those variations that affect the germ cells are inherited