Lamarck's Theory

1. Lamarckism
SANDIP RATHOD

2. Introduction of Organic Evolution
Life can be define as a physicochemical power express reproduction, irritability, adaptation
and locomotion.
1. Abiogenesis: the formation of life from non living substance is called Abiogenesis or
spontaneous generation.
2. Biogenesis: Origin of life from pre-existing life by reproduction.
3. Cosmozoic Theory: the life our planet- earth came from other plants.
4. Theory of eternity of present condition: the universe is unchangeable and life also exists
as such without any change (Not acceptable theory)
5. Theory of catastrophism: the universe has been subjected to distructions of sudden
revolutions at different intervals in the past
6. Theory of special creation: it is based on the Biblical Book of genesis. It says that the Sun,
Earth, Plants, Animal, Man were created by God.
7. Theory of organic Evolution: The theory of organic evolution explain forcefully the origin
of life.
Earth---Inorganic substance—colloidal substance---organic substance- first life.
Sandip Rathod

3. Primitive Earth
Carbon, Hydrogen, Nitrogen oxygen
Water , ammonia methane, hydrogen cyanide
Micro molecules
Amino acid, sugar fatty acid purines Pyrimidines
Macromolecules
Protein, lipid, fats polysaccharides, nucleotide, nuclic acid
Coacervates + Microsphere
Pre-cells
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4. First cell (Anaerobic)
RNA, DNA
Cell (Aerobic Respiration)
Photosynthesis
Protozoa
Mammal
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5. Place of origin of life
It is strongly belied that life originated first in the ocean.
This view is supported by three fact
1. Most of the simpler and lower animals are aquatic.
2. Protoplasm and body fluids contain salts similar to that of the sea.
3. The earliest animal- fossils are obtained from rocks of marine region
The freshwater and land organism are due to later migration from the sea, thus, Sea is
regarded as the mother of life.
Sandip Rathod

6. Lamarckism
• Lamarckism is theory of Organic Evolution .
• Its also called inheritance of acquired characters
• Complex organism are formed from simple organism
• Environment does not remain constant. It change
• Change in environment influence the plant and animals
• Change the environment provide new needs for organism
• In response to the new needs, organism develop new structure
• Variation in organism arises through the effect of use and disuse
• Continuous use makes structural greatly developed, disuse makes the structure atrophied
• Acquired characters
Sandip Rathod

7. Principal of Lamarckism
❑ Internal Urge of organism
❑ Environment and new needs
❑ Use And Disuse theory
❑ Inheritance of acquired characters
Sandip Rathod

8. ❑ Internal Urge of organism
According to Lamarck this increase in size is due to an urge or internal force of
life and due to an inherent ability of organism itself. On the other hand it is due
to desire or some sort of internal urge.
Sandip Rathod

9. ❑ Environment and new needs
New needs arise in animals only change in the environment.
New needs, new habits
Modify the parts
Effects are inherited.
For example, the giraffe, seeking to browse higher and higher on the leaves of trees on which
it feeds, stretches its neck.
Same species of plants grow in different environmental condition.
When plant grow in fertile soil they are healthy and luxuriant
When plant grow in unfertile soil they are weak and thin
Sandip Rathod

10. ❑ Use And Disuse theory
In every animal which has not passed the limit of its
development, a more frequent and continuous use of
any organ gradually strengthens, develops and enlarges
that organ, and gives it a power proportional to the
length of time it has been so used; while the permanent
disuse of any organ gradually weakens and deteriorates
it, and progressively reduces its functional capacity,
until it finally disappears.
Sandip Rathod

11. Web- foot
Biceps Muscles
Eyes of caves animals: Proteus Flight lessness: Kiwi
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12. Sandip Rathod

13. ❑ Inheritance of acquired characters
All the acquisitions or losses wrought by nature on individuals, through the influence of the
environment in which their race has long been placed, and hence through the influence of the
predominant use or permanent disuse of any organ; all these are preserved by reproduction to the
new individuals which arise, provided that the acquired modifications are common to both sexes,
or at least to the individuals which produce the young
Ex. Giraffe, Kiwi
Sandip Rathod

14. Sandip Rathod

15. Criticism of Lamarckism:
C.D. Darlington states that Lamarck's theory is an evergreen superstition.
There were many criticisms for and against Lamarckism. They are as follows
1. Increase in size: organism have the tendency to increase in size. this is true of many organism
but it is not universally applicable.
2. Internal urge: every human being has the desire to fly in the air. If Lamarck principal is
correct, every human being who desires to fly, should develop wings; but it does not occur
Sandip Rathod

16. 3. Use and disuse theory: use organ (eye, heart)
4. Inheritance of acquired characters: Scars, Bored ears, circumcision (cutting off the prepuce
of penis)

17. Sandip Rathod