Darwin would later say that this work caused him to realize the struggle for limited resources was a fact of life.

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She shows how Darwin came to understand that these island animals had differences, developed over time, that helped them survive.

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Darwin's observations showed him that environments can change a little very quickly and a great deal over time.

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Yet it was the work of naturalist Alfred Russel Wallace that pushed Darwin to finally release his theory.

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Another naturalist,Alfred Russel Wallace, had independently written a paper that contained ideas similar to Darwin's concerning evolution.

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That is why author and illustrator Rosalyn Schanzer chose to write the children's book "What Darwin Saw: The Journey that Changed the World."

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Darwin said the Galapagos brought people near "to that great fact that mystery of mysteries the first appearance of new beings on earth."

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There,Darwin noted that levels of rock extending high above the sea contained the fossil remains of shells.

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It was not until eighteen fifty-eight that Darwin was forced to release his theory to the public.

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Miz Schanzer's pictures of Darwin capture the energy and excitement that she sensed in his early writings.

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But it was Darwin who identified and explained the process, natural selection, that causes life to evolve.

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The two became friends. John Henslow suggested that Charles Darwin take the unpaid position of naturalist for a trip on the British ship H.M.S.Beagle.

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Darwin found lizards called iguanas that lived on land and ones that fed in the sea.

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In the late eighteenth century, Darwin's grandfather, Erasmus Darwin,suggested that species evolved from their ancestors.

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She illustrates the unusual tortoises, birds and lizards that Darwin studied in the Galapagos Islands.

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It is important to remember that many of the greatest biological discoveries had yet to be made when Darwin published "On the Origin of Species."

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Darwin noted that all these species were similar to those found in South America.

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But it was on the Galapagos Islands off the coast of Ecuador that Darwin found creatures that made him wonder about how species develop and change.

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In July of that year, Darwin's friends Charles Lyell and Joseph Hooker had studies by both men presented to the scientific group called the Linnean Society of London.

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The idea that species change was not new even in Darwin's time.

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Professor Schmaus notes that,before Darwin, naturalists only collected and named species.

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