Different Theories of EvolutionCuvier and Lamarck

The theory of Georges Cuvier• Georges Cuvier (French, 1769–1832) was a great scientific

thinker.• He studied animals currently on Earth and fossils, and

concluded that they were similar in many ways. • However, he also recognised that living organisms and fossils

were distinctly different.• He championed the idea that fossilised organisms were

separate species from those alive on Earth, and that fossilised organisms lived long long ago.

A trilobite fossil, they no longer exist today

Cuvier continued…• Cuvier argued that the kinds of living things on Earth have

changed over time. • He said that massive geological events occurred that wiped

out many groups of living things, making them extinct.• Then new, different organisms appeared.

Cuvier continued…• This explanation for changes in organisms on Earth over time

is often called catastrophism because the events that made groups of organisms extinct were called catastrophes (say ca-TAS-trow-fees).

Cuvier continued…• While Cuvier found and explained evidence that the kinds of

living things on Earth had changed over time, he did not believe that individual organisms evolved.

• Cuvier considered that each organism functioned so perfectly that any change would destroy the delicate balance that kept the organism alive.

Cuvier continued…• He looked at similarities between different organisms and

explained that they were alike because they performed the same role and not because they were related.

• He studied mummified cats and ibises from ancient Egypt and compared them with living cats and birds.

• He found no changes in their structure to suggest that these species had changed over 4 000 years of time.

The theory of Jean-Baptiste Lamarck• Jean-Baptiste Lamarck (French, 1744–1829) made significant

contributions to the study and classification of plants and invertebrates.

• (He invented the name invertebrates and established the importance of the separation of vertebrates and invertebrates.)

Lamarck continued….• While studying invertebrates (particularly worms and insects),

Lamarck became aware of the many similarities between different species.

• He formulated a theory to explain how so many similar yet different species could have developed.

Lamarck continued…• Lamarck's theory was known as the 'inheritance of acquired

traits'.• This meant that during an individual's lifetime it would react to

the surrounding environment by changing body structures. More use of part of the body leads to the development of that part.

• These changes acquired during a lifetime would then be passed on to the offspring. Thus organisms change from one species to another over a very long period of time.

“Acquired Characteristics”