Lamark’s theory:
Jean baptiste de lamark was a great French naturalist who gave the first theory of evolution.
His theory is known as lamarkism, after his name. This theory is also known as “inheritance of acquired characters”. In his book “philosaphie zoologiave” he mentioned the cause of evolution. The postulates of Lamark’s theory are:
Tendency to grow:
Formation of new organs
Use and disuse of organ
Inheritance of acquired characters
Tendency to grow: this is the first principle of Lamark’s theory. According to this principle, each and every organism wants to grow maximum in size. They wants to become complex in structure. The internal force and external (environment) influence organism to become complex. E.g. presence of tentacles in snails
Formation of new organs: this is the 2nd principle of Lamark’s theory. According to this principle, any organism can develop new organs if urgently needed to that organism. The formation of new organ depends upon the need of that organism. They require new organs to adapt in changing environment. Environment also influence organism for formation of new organs. E.g. duck developed webbed feet to swim in water.
Use and disuse of organs: this is 3rd principle of Lamark’s theory. According to this principle, any organs become developed when continuously used and becomes reduced when disused. Disused organ remains functionless or vestigial in that organism. E.g. ancient giraffe had short neck; they developed long neck due to continuous use of neck to get leaves of tall trees.
Inheritance of acquired characters: The character gained by living being during their lifetime is called as acquired characters. The characters acquired during the lifetime of an individual are transmitted to their offspring according to this principal. In the off springs, this modification becomes pronounced, depending upon continuous use or disuse of organ. Lamark believe that in every generation, new character are gained and transmitted to new generation. These characters are accumulate generation after generation and the offsprings thus produced becomes totally different from original parents. Thus after many generations, a new species is formed.
Drawbacks of lamarkism:-
According to Lamark’s theory, all organisms tend to become complex. Many plants contradict it by showing reduced character. E.g. more developed flowering plants are usually much smaller in size.
The inheritance of acquired character, on which the theory is based was opposed by German scientist august Weismann. He cut the tail of mice upto 22th generation to see the effect on tail length, but there was no change in length. According to august, acquired characters are not transmitted to next generation.
The muscles of the shoulder of black smith develops due to constant use but is not inherited to their off springs.
Boring of ear and nose in women is the culture that is running from centuries but their offsprings are not born with even a trace of holes.
Hence lamarkism is not accepted these days and is proved false.
Jean baptiste de lamark was a great French naturalist who gave the first theory of evolution.
His theory is known as lamarkism, after his name. This theory is also known as “inheritance of acquired characters”. In his book “philosaphie zoologiave” he mentioned the cause of evolution. The postulates of Lamark’s theory are:
Tendency to grow:
Formation of new organs
Use and disuse of organ
Inheritance of acquired characters
Tendency to grow: this is the first principle of Lamark’s theory. According to this principle, each and every organism wants to grow maximum in size. They wants to become complex in structure. The internal force and external (environment) influence organism to become complex. E.g. presence of tentacles in snails
Formation of new organs: this is the 2nd principle of Lamark’s theory. According to this principle, any organism can develop new organs if urgently needed to that organism. The formation of new organ depends upon the need of that organism. They require new organs to adapt in changing environment. Environment also influence organism for formation of new organs. E.g. duck developed webbed feet to swim in water.
Use and disuse of organs: this is 3rd principle of Lamark’s theory. According to this principle, any organs become developed when continuously used and becomes reduced when disused. Disused organ remains functionless or vestigial in that organism. E.g. ancient giraffe had short neck; they developed long neck due to continuous use of neck to get leaves of tall trees.
Inheritance of acquired characters: The character gained by living being during their lifetime is called as acquired characters. The characters acquired during the lifetime of an individual are transmitted to their offspring according to this principal. In the off springs, this modification becomes pronounced, depending upon continuous use or disuse of organ. Lamark believe that in every generation, new character are gained and transmitted to new generation. These characters are accumulate generation after generation and the offsprings thus produced becomes totally different from original parents. Thus after many generations, a new species is formed.
Drawbacks of lamarkism:-
According to Lamark’s theory, all organisms tend to become complex. Many plants contradict it by showing reduced character. E.g. more developed flowering plants are usually much smaller in size.
The inheritance of acquired character, on which the theory is based was opposed by German scientist august Weismann. He cut the tail of mice upto 22th generation to see the effect on tail length, but there was no change in length. According to august, acquired characters are not transmitted to next generation.
The muscles of the shoulder of black smith develops due to constant use but is not inherited to their off springs.
Boring of ear and nose in women is the culture that is running from centuries but their offsprings are not born with even a trace of holes.
Hence lamarkism is not accepted these days and is proved false.
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