Vocabulary

evolution strata natural selection adaptation fitness figure 15-1

Charles Darwin first studied to be a doctor and then a minister, but was also interested in nature. At the age of 22, he set off on a five-year voyage that became an important part of the history of science.

figure 15-2

The strata of the Grand Canyon contain evidence of the history of the area over millions of years of geologic time.

figure 15-2

The strata of the Grand Canyon contain evidence of the history of the area over millions of years of geologic time.

Word Roots and Origins evolution from the Latin prefix e-, meaning "out," and volvere, meaning "to roll"

iniemei conned

www.scilinks.org Topic: Evolution Keyword: HM60546

INKS,

Maintained by the National Science Taachers Association iniemei conned

www.scilinks.org Topic: Evolution Keyword: HM60546

Ideas About Geology

By the 1800s, scientists in Europe had begun to study rock layers—called strata—such as those shown in Figure 15-2. They found that strata are formed as new layers of rock are deposited over time. They inferred that, in general, lower strata were formed first and are thus the oldest. The scientists also found that different rock strata hold fossils of different kinds of organisms.

French anatomist Georges Cuvier (coo-VYAY) (1769-1832) spent years reconstructing the appearance of unique organisms from fossil bones. Cuvier gave convincing evidence that some organisms in the past differed greatly from any living species and that some organisms had become extinct, meaning the species had ceased to live after a point in time. Cuvier also found that deeper and older strata hold fossils that are increasingly different from living species. Finally, Cuvier found many "sudden" changes in the kinds of organisms found in one rock stratum compared to the next.

To explain these observations, Cuvier promoted the idea of catastrophism (kuh-TAS-truh-Flz-uhm)—the idea that sudden geologic catastrophes caused the extinction of large groups of organisms at certain points in the past. Even though scientists no longer accept all of his explanations, Cuvier contributed to scientific acceptance that geologic change and extinction had occurred.

The English geologist Charles Lyell (1797-1875) shared some of Cuvier's ideas but thought that the geologic processes that have changed the shape of Earth's surface in the past continue to work in the same ways. Lyell's idea is called uniformitarianism (YOON-uh-FAWRM-uh-TER-ee-uhn-lz-um). Charles Darwin read Lyell's writings while on his trip around the world. He was excited to find how well Lyell's ideas fit with his own observations and ideas. Lyell had shown evidence from geology that fit with Darwin's evidence from biology. Darwin referred to Lyell's work in many of his writings.

Lamarck's Ideas on Evolution

The French biologist Jean Baptiste Lamarck (1744-1829) also supported the idea that populations of organisms change over time. Lamarck put forward a new idea to explain how evolution could happen, though this idea is no longer accepted among scientists. Lamarck thought that simple organisms could arise from nonliving matter. He also thought that simple forms of life inevitably develop into more complex forms. He proposed that individuals could acquire traits during their lifetimes as a result of experience or behavior, then could pass on those traits to offspring. Lamarck's idea is called the inheritance of acquired characteristics. Even though Darwin himself once accepted Lamarck's idea, it was rejected by many scientists of their time and has not been supported by modern scientific study of the mechanisms of inheritance.

North

America Atlantic

Ocean

Galápagos Islands

South America.

Europe

Asia

Africa

Indian Ocean

Pacific Ocean

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