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1

name 4 postulates of Lamarckism

1. Theory of elan vitae or growth
2. Theory of environment pressure needs and spontaneous formation of organs
3. theory of use and disuse
4. Theory of Inheritance of acquired characters

2

Theory of elan vitae or growth

The internal forces of life tend to increase the size of an organism by growth and systems.

3

Theory of environment pressure need and spontaneous formation of organs

New organs and systems are formed because of need or want which has arisen due to continuous environment pressure on the organism

Change in environment can bring change in organs.

Infertile and fertile soil relation to plant growth.

4

Theory of use or disuse

The development of an organ is directly proportional to its use; continuous use strengthen the organ while disuse weakens it.

5

Theory of inheritance of acquired characters

all the changes in organisms acquired during life time are transmitted to the next generation k/a inheritance of acquired characters

6

Mechanism of lamarckism

Flowchart

in one-note

7

Critics of Theory of elan vitae or growth

often evolution proceeded without increase in size rather reduction in size

Many ferns and conifers which became extinct were once a gigantic tree.

8

Critics of Theory of environment pressure need and spontaneous formation of organs

the desire of man can not lead to formation of new structure.

Many wanted to fly but never got wings.

9

Critics of Theory of use or disuse

heart is not increasing its size inspite of its continuous use.

10

Critics of Theory of inheritance of acquired characters

Germplasm theory
Cutting mice tail for 20 generation to observe length of tail not getting any shorter. means, Acquired characters (mutilated tails) were not inherited.

11

Germplasm theory

Given by August Weismann
Organism is made up of Somatic cell and Germ cell.
Somatic cell constitute all body cell except the germ cell of the gonads and they perish with death of animal. Any character acquired by somatic cell is not transmitted to the progeny.
The germ cell through gametes of parents are transmitted from parents to offspring and character is transmitted to offspring.