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Diff Theories

Lamarckism, proposed by Jean Baptiste de Lamarck in 1809, is the theory of inheritance of acquired characters, emphasizing adaptation as a means of evolutionary change. It is based on four postulates: the emergence of new needs due to environmental changes, the use and disuse of organs affecting their development, and the belief that acquired characteristics can be inherited by offspring. This theory suggests that organisms adapt to their environments through changes in their habits and physical traits during their lifetime.

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33 views1 page

Diff Theories

Lamarckism, proposed by Jean Baptiste de Lamarck in 1809, is the theory of inheritance of acquired characters, emphasizing adaptation as a means of evolutionary change. It is based on four postulates: the emergence of new needs due to environmental changes, the use and disuse of organs affecting their development, and the belief that acquired characteristics can be inherited by offspring. This theory suggests that organisms adapt to their environments through changes in their habits and physical traits during their lifetime.

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Atul Dimble
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I.

Lamarckism:
It is also called “Theory of inheritance of acquired characters” and was proposed
by a great French naturalist, Jean Baptiste de Lamarck (Fig. 7.34) in 1809 A.D. in
his famous book “Philosphic Zoologique”. This theory is based on the comparison
between the contemporary species of his time to fossil records.

Jean Baptiste de Lamarck

His theory is based on the inheritance of acquired characters which are defined as
the changes (variations) developed in the body of an organism from normal
characters, in response to the changes in environment, or in the functioning (use
and disuse) of organs, in their own life time, to fulfill their new needs. Thus
Lamarck stressed on adaptation as means of evolutionary modification.

A. Postulates of Lamarckism:
Lamarckism is based on following four postulates:

1. New needs:

Every living organism is found in some kind of environment. The changes in the
environmental factors like light, temperature, medium, food, air etc. or migration
of animal lead to the origin of new needs in the living organisms, especially
animals. To fulfill these new needs, the living organisms have to exert special
efforts like the changes in habits or behaviour.

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2. Use and disuse of organs:

The new habits involve the greater use of certain organs to meet new needs, and the
disuse or lesser use of certain other organs which are of no use in new conditions.
This use and disuse of organs greatly affect the form, structure and functioning of
the organs.

Continuous and extra use of organs make them more efficient while the continued
disuse of some other organs lead to their degeneration and ultimate disappearance.
So, Lamarckism is also called “Theory of use and disuse of organs.”

So the organism acquires certain new characters due to direct or indirect


environmental effects during its own life span and are called Acquired or adaptive
characters.

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3. Inheritance of acquired characters:

Lamarck believed that acquired characters are inheritable and are transmitted to
the offsprings so that these are born fit to face the changed environmental
conditions and the chances of their survival are increased.

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