Presentation lamarckism evolution ecology

Lamarckism

1. Submitted by – sonal Tiwari roll no. :- 22014583007 Course : - B.sc life sciences semeseter : - IV submitted to :- Dr. kamlesh Negi

2. Lamarckism & Neo- lamarckism

3. __Introduction__ Lamarckism was proposed by Jean-Baptiste de Monet Lamarck in the year 1744-1829. This theory was based on the principle that all the physical changes occurring in an individual during its lifetime are inherited by its offspring. For eg ., the development of an organ when used many times. This theory has been explained here.

4. Lamarck’s Theory Lamarck’s theory includes four main propositions:

5. Change Through Use And Disuse The organs which are used frequently by the organism develop and the characteristics that are used seldom are lost in the succeeding generations. For eg ., a giraffe stretches its neck to eat leaves, a “nervous fluid” would flow in its neck and it enlarges. The organs which the organisms have stopped using would shrink with time.

6. Effect of Environment and New Needs The environment influences all the organisms. A slight change in the environment brings about changes in the organisms. This gives rise to new needs which in turn produces new structures and changes the habits of the organisms.

7. Inheritance of Acquired Characters An individual acquires certain characteristics during its lifetime. These characters are inherited by their offspring as well. He explained this with an example of a blacksmith. A blacksmith has strong arms due to the nature of their work. He proposed that any children a blacksmith conceives will inherit the development of strong muscles.

8. Examples of Lamarckism Evolution of giraffe The ancestors of the giraffe looked like horses with small necks and forelimbs. They lived in areas where there was no surface vegetation. Therefore, they had to stretch their neck and forelimbs to eat leaves from tall plants. Consequently, these parts got elongated. This trait was transmitted in the successive generations.

9. Neo- Lamarckism It is a modification of the original theory of Lamarck in order to make it more suitable to modern knowledge The theory stresses on the direct effect of changed environment on the organisms. Only those modifications are transferred to the next generation which influence germ cells or where somatic cells give rise to germ cells. Neo-Lamarckism does not give any importance to these factors.

10. The various propositions of Neo-Lamarckism are The driving force for evolution is the environment.
Change in the environment brings about changes in the heredity of the organisms.
A number of variations appear in the organisms. At least some of the variations are transferred to the next generation.
Variations passed on to the progeny are those which influence germ cells or the germ cells are formed from the affected somatic cells.

11. Thank you