Jean Baptiste LAMARCK 1744 1829

THEORY OF INHERITANCE OF ACQUIRED CHARACTERSJean Baptiste Lamarck and the

Personal History

Born in in Bazentin-le-Petit, France Joined the French army at 17 when his father passed away While enlisted he studied plants in his free time After 7 years in the army he became injured and was forced to leave He then went on to study medicine and botany He was only 34 when he wrote a book on plants (Flore Franaise)

LAMARCKS THEORY OF INHERITANCE OF ACQUIRED CHARACTERS

Organisms tend to increase in size and complexity with timeChanges in environment made special demands on organisms. Formation of new organ in the body is the results of a specific need felt by the animalThe extend of the development of organs and their efficiency is proportional to their use and disuse of the organs.The observable characteristic acquired by the parents during their lifetime can be transmitted through reproduction to the offspring.

Adaptation and SpecialisationLamarck noticed that organisms adapted to a particular place had well developed specialised organsFor example a carnivore will have long canine teeth to grip its prey

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The Law of Use and DisuseHe proposed that if an organ is used a lot it will develop and strengthen If it is not used it will degenerateHe called this the law of use and disuse

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Vestigial OrgansSmall non-functional organs (vestigial organs) Comparative anatomy showed that these organs resembled those which were much more developed, with particular functions, in other speciese.g. the appendix in humans, the internal hind limbs of whales, and the internal legs of some species of snakes (Python and Boa constrictor)

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APPENDIX (HUMAN)

INTERNAL HIND LIMBS OF WHALES

Lamarcks most famous illustration was using the giraffe as an exampleThe long neck of the giraffe has evolved as a result of generations of giraffes stretching their necks to feed on the leaves of tall trees due to food shortageEach generation has transmitted to its offspring a small increase in length caused by continual stretchingThe modern giraffe thus has a very long neck due to inheritance of the acquired characteristic

Lamarck vs. DarwinLamarcks theory required adaptation to create new variationsThis was followed by the inheritance of these characteristicsDarwins theory requires random hereditary variation first, followed by selection of the variationsThe argument was over when Mendels laws of genetics were rediscovered at the end of the 19th centuryVariations are due to hereditary traits passing from one generation to the next in predictable frequencies

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Disproving LamarckCharacteristics acquired during the lifetime of a parent are not passed onto the offspringAn athlete who develops a large muscle mass through training does not have children who already possess this large muscle massErnst Haeckel:In an attempt to disprove Lamarckism he is said to have cut off the tails of mice for several generationsThe babies born from this line of tailless mice still grew tails as long as their ancestorsThis was not exactly a fair test as the mice had not stopped using their tails in an attempt to adapt to their environmentThey still found their tails useful

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Wrap-up video