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Lamarck

Jean Baptiste Lamarck was an early French naturalist and biologist who proposed one of the first evolutionary theories. He believed that organisms could pass on traits acquired during their lifetime to their offspring, and that living things evolved in a continuous upward progression toward greater complexity. For example, Lamarck argued that giraffes developed longer necks through generations of stretching to reach higher tree leaves, and then passed this elongated neck trait to subsequent offspring. While Lamarck's inheritance of acquired characteristics theory was later disproven, he made important early contributions to recognizing evolution and the role of the environment in shaping species.

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293 views9 pages

Lamarck

Jean Baptiste Lamarck was an early French naturalist and biologist who proposed one of the first evolutionary theories. He believed that organisms could pass on traits acquired during their lifetime to their offspring, and that living things evolved in a continuous upward progression toward greater complexity. For example, Lamarck argued that giraffes developed longer necks through generations of stretching to reach higher tree leaves, and then passed this elongated neck trait to subsequent offspring. While Lamarck's inheritance of acquired characteristics theory was later disproven, he made important early contributions to recognizing evolution and the role of the environment in shaping species.

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HANNA ANGELA LEJANO
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Jean Baptiste Lamarck

Jean-Baptiste Pierre Antoine de


Monet, chevalier de Lamarck, often
known simply as Lamarck, was a
French naturalist, biologist, academic,

and soldier. He was an early

proponent of the idea that biological
evolution occurred and proceeded in
accordance with natural laws.

Although the name "Lamarck" is now associated with a discredited view of


evolution, the French biologist's notion that organisms inherit the traits acquired
during their parents' lifetime had common sense on its side. In fact, the
"inheritance of acquired characters" continued to have supporters well into the
20th century.
Jean Baptiste Lamarck (1744-1829) is one of the best-known early
evolutionists. Unlike Darwin, Lamarck believed that living things evolved in a
continuously upward direction, from dead matter, through simple to more
complex forms, toward human "perfection." Species didn't die out in
extinctions, Lamarck claimed. Instead, they changed into other species. Since
simple organisms exist alongside complex "advanced" animals today,
Lamarck thought they must be continually created by spontaneous
generation.

According to Lamarck, organisms altered their behavior in response to


environmental change. Their changed behavior, in turn, modified their
organs, and their offspring inherited those "improved" structures. For
example, giraffes developed their elongated necks and front legs by
generations of browsing on high tree leaves. The exercise of stretching up to
the leaves altered the neck and legs, and their offspring inherited these
acquired characteristics.
According to Darwin's theory, giraffes that happened to have slightly
longer necks and limbs would have a better chance of securing food and
thus be able to have more offspring -- the "select" who survive.

Conversely, in Lamarck's view, a structure or organ would shrink or


disappear if used less or not at all. Driven by these heritable
modifications, all organisms would become adapted to their

environments as those environments changed.

Lamarck held that evolution was a constant process of striving toward


greater complexity and perfection.
Even though this belief eventually
gave way to Darwin's theory of natural selection acting on random
variation, Lamarck is credited with helping put evolution on the map and
with acknowledging that the environment plays a role in shaping the
species that live in it.
The Theory Of Need
-Organisms change in response to their environment
The Theory Of Use And Desuse
-Organs not in use will disappear while organs in use will develop.
The Theory Of Acquired Characteristics

-Acquired characteristics were believed to be inherited by their offsprings and


propagated by the next generation.
After the discovery of modern genetics, lamarck's theory of the
inheritance of acquired traits was completely rejected. Organisms cannot
force themselves to adapt (random mutations are required), and acquired
characteristics are not inherited. And remember, the knowledge of
genetics did not exist in his time. Therefore, he knew nothing about genes
or mutation.

The ancestors of giraffes carry the correct gene for long, and strong
necks. They did not acquire the gene by straining or stretching their
necks.

This theory was not accepted because genetic information can only be passed
on to their offspring through sex cells, not body cells.

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