AND NEO LAMARCKISM
v Jean-Baptiste Lamarck is a
French Naturalist who lived during the period of 1744-1829. Lamarck has
published books in the field of Invertebrate
Zoology and Paleontology. The
popular book called Système des animaux sans vertèbres was
written by Lamarck.
v Lamarckism is the theory of organic Evolution
proposed by Lamarck. It explains about the origin of new species. It is also
known as theory of inheritance of acquired
v Lamarckism consists of four postulates. They are
Ø Law of inherent capacity – Animals and plants has the
ability to grow and increase in Size to attain a maximum growth. According to
Lamarck, this tendency of the organisms is due to the internal urge in them to
increase in size
Ø Environment and new need-organism
develop new characters based on the Environmental and their own need.
Ø Use and disuse Theory-If a
particular part or organ is used or not used for a long time it will result in
increase or decrease in size of that
organ. Example is neck of Giraffe.
Ø Inheritance of acquired characters-The transmission of characters developed by the organism during its life
time. Example loss of eyes in cave dwelling organisms.
v The first two theories of Lamarck were accepted but objections arose to the other two theories of
acquired characters because he didn’t distinguish heritable from non-heritable characters
and explained only the importance of the character or the change not its origin and mechanism
v An example for objection to third law was no
increase in size of blood vessels
though they were used continuously.
v An example for objection to fourth law was no pierced ears were
seen in newly born babies who parents have pierced ears. It was officially
disproved by August Weismann by proposing Germplasm
v As a result of these discrepancies, Neo Lamarckism was
proposed. It is a modern version of Lamarckism. Many scientists have
contributed for the development of Neo Lamarckism.
v George Henslow 1835–1925 wanted to study
the Evolution of plants based on the effect of environmental stress on growth
v Edward Drinker Cope and Alpheus Hyatt studied
fossils to see the evolutionary trends.
v Samuel Butler thought
that the evolution of the organism is shaped by the Inheritance of acquired characters.
v Theodor Eimer combined the Lamarckism
concept with orthogenesis.
v Ernst Haeckel supported the concept of Lamarckism.
Thus Lamarckism and Neo Lamarckism have contributed a lot to study the