Neo – Lamarkism (Theory of Evolution)
Definition : Modified Lamarkism which states that environment induces variation and only germinal variations are inheritable.
Introduction : Lamarkism proved to be unsatisfactory in explaining evolution. But then, long forgotten Lamrkism was enlightened with the new knowledge of genetics, giving rise to Neo-Lamarkism. Neo – Lamarkism confirmed that environment plays a significant role in deciding form, structure, color, size etc. of an organism and these characters are heritable.
Main scientists who contributed are : French Giard, T.H Morgan, Spen cer, Tower, A.S. Packard, Bonner, etc.
Neo Lamarkism states that :
(1) Changes in environmental factors in duces variations : Environment affect on germ cells. Through somatic cells. And in such cases, the variations in one generation are inheritable. Eg. When a pale variety of moth (selenia bilunaria) was fed on manganese coated food, a true breeding Melanie variety of moth was produced.
- Environment affect directly on Zero Cells When, tower exposed young ones of some potato beetles to temperature fluctuation, he found that present beetle generation was unaffected with no somatic changes but next generation had marked changes in body colouration so as to resist any temperature fluctuation.
- Muller also confirmed mutagenic role of X – rays on Drosophilla, causing mutation in Drosophila melanogaster.