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Chapter 2

Chapter 2. Evolutionary Theory. Introduction. Evolution What is your reaction to this term? Biological sciences Humans and Apes shared last common ancestor 5-8 million years ago. History of Evolutionary Thought. Discoveries came over a long time from a lot of sources Charles Darwin

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Chapter 2

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  1. Chapter 2 Evolutionary Theory

  2. Introduction • Evolution • What is your reaction to this term? • Biological sciences • Humans and Apes shared last common ancestor 5-8 million years ago.

  3. History of Evolutionary Thought • Discoveries came over a long time from a lot of sources • Charles Darwin • Alfred Russel Wallace • Middle Ages • Thought processes were static • Greek influence – Aristotle • Scientific Revolution • Europe vs. Arabia and India

  4. Early Evolutionary Thinkers • John Ray (1627-1705) • Coined terms species and genus • Carolus Linnaeus (1707-1778) • Fixity of species • George-Louis Le Clerc de Buffon (1707-1788) • Change does occur in the universe • Erasmus Darwin (1731-1802) • Charles Darwin’s Grandfather • Jean-Baptiste Lamarck (1744-1829) • First to propose evolutionary process

  5. Evolutionary Thinkers Con’t. • Georges Cuvier (1769-1832) • Opponent of Lamarck • Charles Lyell (1797-1875) • Wrote Principles of Geology • Thomas Malthus (1766-1834) • English clergyman and economist • Mary Anning (1799-1847) • Discovered a lot of fossils

  6. Lamarck • John BaptisteLamack was the first scientist to produce an explanation for the evolutionary process. • He believed that species change was influenced by environmental change.

  7. Cuvier • Georges Cuvier introduced the concept of extinction and the theory of catastrophism. • The view that the earth’s geological landscape is the result of violent cataclysmic events. • Cuvier promoted this view, especially in opposition to Lamarck.

  8. Thomas Malthus • Thomas Malthus wrote about the relationship between food supply and population increase. • His essay on the Principle of Population led both Darwin and Wallace to the principle of natural selection.

  9. Charles Lyell • Charles Lyell developed the theory of uniformitarianism.

  10. Mary Anning • Discovered the first complete fossil of Ichthyosaurus, a large fishlike marine reptile. • She became known as one of the world’s leading “fossilists” and contributed to the understanding of the evolution of marine life over 200 million years ago.

  11. Charles Darwin (1809-1882) • Ideas were formed while serving as a naturalist on the voyage of the HMS beagle. • Darwin saw the importance of biological variation within a species. • Recognized the importance of sexual reproduction in increasing variation. • By 1844, Darwin had complete the work that he would publish fifteen years later.

  12. Alfred Russell Wallace(1823-1913) • A naturalist who worked in South America and Southeast Asia. • Suggested species descended from other species and new species were influenced by environmental factors. • Presented paper on evolution and natural selection to the Linnean Society of London jointly with Darwin.

  13. Discovery of Natural Selection • Charles Darwin (1809-1882) • Discovered first credible mechanism for evolutionary change • HMS Beagle • Finches and barnacles • Alfred Russel Wallace (1823-1913) • Developed own theory of natural selection • Wrote letter to Darwin

  14. The Path of the HMS Beagle

  15. Natural Selection • Darwin’s formulation included: • Potential for reproductive rates that outpace the rate of food supply • The presence of biological variation within all species • Constant competition among individuals for survival • Favorable traits = increase in reproduction • Environment determines favorable traits • Favorable traits passed to offspring • Over long periods of time, successful variations accumulate in populations • Geographical isolation may result in new species

  16. Contrasting Views on Evolution

  17. Natural Selection in Action • Peppered moth in the UK • Galapagos birds and beak thickness

  18. Domestic Dog Breeds • The variation exhibited by dog breeds has been achieved in a relatively short time through artificial selection.

  19. Evolutionary Change Through Natural Selection • A trait must be inherited if natural selection is to act on it. • Natural selection can’t occur without population variation in inherited characteristics. • Fitness is a relative measure that changes as the environment changes. • Natural selection can only act on traits that affect reproduction.

  20. Constraints on 19th Century Evolutionary Theory • No one knew source of variation that Darwin explained • Did not know how favorable traits were passed down. • Laws of heredity unknown – Mendel had not come on the scene • DNA was not discovered until 1953

  21. Opposition to Evolution • Offensive to Christians because in conflict with Biblical versions of creation • Evolution considered to be a fact by most scientists today • Accepted in part by Catholic Church and most Protestants • Fundamentalists reject evolution • Creationism • Intelligent Design • Debate topic: • Should evolution be taught in public schools? If so should Creationism also be taught?

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