Quiz 6: Organic Evolution


French biologist Jean Baptiste de Lamarck proposed an evolutionary mechanism called inheritance of acquired characteristics. According to this theory, organisms by striving to meet the demands of their environments acquire adaptations and pass them to their offspring by heredity. He presented the example of the giraffe by stating that giraffe evolved its long neck because its ancestors lengthened their necks by stretching to obtain food and then passed this lengthened neck to their offspring. Over many generations, these changes accumulated to produce the long necks of modern giraffes. Lamarckian concept of evolution is also called transformational, as it claims that individual organisms can transform their characteristics through the use and disuse of parts. These Transformational theories were rejected because genetic studies show that traits acquired by an organism during its lifetime are not passed onto offspring.

Principle of uniformitarianism was proposed by geologist Sir Charles Lyell. Uniformitarianism is composed of two important principles: • The laws of physics and chemistry have not changed throughout the history of the earth. • Past geological events have occurred by natural processes which are similar to those observed today. Lyell proposed that natural forces that have been acting over long periods of time could explain the formation of fossils-bearing rocks. Lyell's geological studies led him to conclude that the earth's age must be measured in millions of years. Lyell also said that the geological changes seen were gradual and occurs over time. He argued that such change have no inherited tendency to occur in any particular direction. Both of these claims left important marks on 's evolutionary theory.

During five years of voyage (1831 to 1836) on the Beagle , made many stops along the coasts of and adjacent islands. This journey was very important to his thinking because: • made extensive collections and observations on the fauna and flora of these regions. • He unearthed numerous fossils of animals which were long extinct and noted the resemblance between the fossils of South America pampas and the known fossils of. • He encountered seashells In the embedded in rocks at 13,000 feet. • He experienced an earthquake and watched mountain torrents that relentlessly wore away the soil. • In the he documented the unique character of the Galapagos plants and animals, including tortoises, marine iguanas, mocking-birds, and ground finches. These observations and his reading of Lyell's "Principles of Geology" during this voyage strengthened his idea that natural forces could explain the geological features of the earth.

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