Transcript LAMARCKIAN EVOLUTION

LAMARCKIAN
EVOLUTION
© 2008 Paul Billiet ODWS
Jean Baptiste LAMARCK
1744 – 1829
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Lamarck rejected
fixity
He proposed a theory
of evolution which is
attractive but it was
eventually rejected
because of the way
inheritance works
Lamarck
© 2008 Paul Billiet ODWS
Adaptation and specialisation
Lamarck noticed that organisms adapted
to a particular niche had well developed
specialised organs
 For example a carnivore will have long
canine teeth to grip its prey
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© 2008 Paul Billiet ODWS
vestigial organs
Small non-functional organs (vestigial
organs)
 e.g. the appendix in humans, the internal
hind limbs of whales and the internal legs
of some species of snakes
 Comparative anatomy showed that these
organs resembled those which were much
more developed, with particular functions,
in other species
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© 2008 Paul Billiet ODWS
The Law of Use and Disuse
He proposed that if an organ is used a lot
it will develop and strengthen
 If it is not used it will atrophy
 He called this the law of use and disuse
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© 2008 Paul Billiet ODWS
The Inheritance of Acquired
Characteristics
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if an organism developed a characteristic feature
through adapting to a new way of life during its
lifetime, it would pass this on to its offspring
The classic example given is that of the giraffe’s
neck
As the giraffe’s ancestors searched for a richer
food supply they stretched to reach higher
branches in trees
Thus their stretched bodies were passed onto
their offspring
© 2008 Paul Billiet ODWS
Lamarck v Darwin
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Lamarck’s theory required adaptation to create
new variations
This was followed by the inheritance of these
characteristics
Darwin’s theory requires random hereditary
variation first, followed by selection of the
variations
The argument was over when Mendel’s laws of
genetics were rediscovered at the end of the 19th
century
Variations are due to hereditary traits passing
from one generation to the next in predictable
frequencies
Disproving Lamarck
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Characteristics acquired during the lifetime of a
parent are not passed onto the offspring
An athlete who develops a large muscle mass
through training does not have children who
already possess this large muscle mass
Ernst Haeckel
In an attempt to disprove Lamarckism he is said
to have cut off the tails of mice for several
generations
The babies born from this line of tailless mice still
grew tails as long as their ancestors
This was not exactly a fair test as the mice had
not stopped using their tails in an attempt to
adapt to their environment
They still found their tails useful
Lamarckism in evolution theory
today
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Behaviour can be different
Some behaviour patterns are innate and will also
evolve in by natural selection
learned behaviour patterns can be changed
within a generation
Members of a social group who have acquired the
behaviour in their lifetimes will pass these
learned skills onto others including their children
This pattern of evolution resembles the
Lamarckian pattern
The evolution of learnt behaviour is much faster
than genetic evolution and it plays an important
role in human cultural evolution