Neo lamarckism

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1. Muhammad Jawad 04021813031 Neo-Lamarckism

2. Edward drinker cope (July 28,1840—April 12,1897) was an American paleontologists and comparative anatomist. He was a founder of Neo-Lamarckism school of thought. 5/5/2019 2

3. Neo-Lamarckism A theory of inheritance based on a modification and extension of Lamarckism, essentially maintaining the principle that genetic changes can be influenced and directed by environmental factors. 3 5/5/2019

4. Origin of Neo-Lamarckism: The period of the  history of evolutionary thought  between Darwin's death in the 1880s, and the foundation of  population genetics  in the 1920s and the beginnings of the modern evolutionary synthesis in the 1930s, is called  the eclipse of Darwinism  by some historians of science. During that time many scientists and philosophers accepted the reality of evolution but doubted whether natural selection was the main evolutionary mechanism. 5/5/2019 4

5. Among the most popular alternatives were theories involving the inheritance of characteristics acquired during an organism's lifetime. Scientists who felt that such Lamarckian mechanisms were the key to evolution were called Neo- Lamarckians . 5/5/2019 5

6. Lamarckism The theory lays stress on internal vital force, appetency and use and disuse of organs. It believes that change in environment brings about a conscious reaction in animals. According to Lamarckism the acquired characters are pass on to the next generation. Neo-Lamarckism It does not give any importance to these factors. The theory stresses on the direct effect of changed environment on organisms. Normally on these modifications are transferred to the next generation which influence germ cells or where somatic cells give rise to germ cells. 5/5/2019 6

7. Drawbacks of Lamarckism lead to Neo-Lamarckism: Lamarckism has many drawbacks and this is evident from the experiments carried out by various scientists. Experiments such as the one carried out by Weismann in which he mutilated the tails of white rats and mated them nut found no loss of tail in succeeding generations. 5/5/2019 7

8. McDougall’s (1938) experiment on rats to observe that acquired behavioral traits are inherited or not etc. Limitations of Lamarckism as were shown by many researchers led to the formation of new school of thought that support evidences in support of Lamarckism. 5/5/2019 8

9. Harrison, Tower and Muller performed experiments and concluded some points.  Germ cells are influenced by the environmental changes.  Germ cells may carry acquired or somatic variations to the offspring.( Harrison)  Germ cells may be affected directly by the environmental factors.( Tower)  Somatic traits are the products of nature and nurture i.e. genes and environmental interaction. This infers that environment affect the gene expression of organisms. 5/5/2019 9