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Lamarck Vs Darwin
Theory 1
Theory 2
Larmarck was one of the earliest to develop a
theory on evolution. His observations showed
that each kind of organism had adapted to live in
its environment. These adaptations occurred over
a long period due to the way the organism used
its body parts. Those body parts that are not used
regularly to help them survive in the environment
would not be needed. This is the Law of Use and
Disuse. Larmarck explained his theory of
evolution through inheritance of acquired
characteristics. These characteristics are passed
on to the next generation. The flaw to this theory
is that we now know that genes are passed on
from on generation to the next. These genes
provide the characteristic of the organism and
these characteristics do not change within the life
of the organism. The body cells may change, but
this does not mean that the sex cells will. An
experiment was done to prove this. The tails of
mice were cut off and their offspring always had
their tails when they reproduced. This was done
over 20 generations and the same results
occurred. A mutation in a sex cell could cause a
change in the offspring, but not in body cells.
Darwin recognized that there was much
variation within species. These variations or
differences allowed certain organisms to be
more successful in their environment than
others. This is called natural selection. When
the environment changes natural selection will
allow the strong to flourish. This is called
survival of the fittest. Those individuals that
have specific traits that are advantageous for
them to be more successful in obtaining food
and escaping predators than others. This is now
the accepted theory.
Example: Giraffe
Example: Giraffe
Giraffe live in dry regions were leaves are high.
Giraffes had to reach and stretch their necks to
reach the high leaves. This constant stretching
caused the necks to stretch over time. This
change in the size of the neck was passed onto
their offspring, which means that all future
generations would also had longer necks.
Giraffes had shorter necks than what they have
today. However, each giraffe had different
neck sizes. The longer neck giraffes were able
to reach the high leaves and therefore had more
food available than those giraffes that had short
necks. This means that the long necked giraffes
had better success of survival than the shortnecked giraffes. The long necked giraffes
produced more offspring and passed on the
gene of long necks to their offspring. This did
not occur within one generation, but occurred
over many thousands of generations.
Summary
Lamarck
Darwin
Evolutionary time
Over a long period of time
Over a long period of time
Role of environment
Environment causes change
Environment selects favorable
variations
Role of the organisms
Organism attempts to strive
and change.
No attempt to change