End Show Slide 1 of 20 Darwin’s Theory of Evolution Biology Copyright Pearson Prentice Hall

End Show 15-1 The Puzzle of Life's Diversity Slide 2 of 20 Copyright Pearson Prentice Hall 15-1 The Puzzle of Life's Diversity Evolution is the process by which modern organisms have descended from ancient organisms. A scientific theory is a well-supported testable explanation of phenomena that have occurred in the natural world The Puzzle of Life's Diversity

End Show 15-1 The Puzzle of Life's Diversity Slide 3 of 20 Copyright Pearson Prentice Hall Voyage of the Beagle In 1831, Darwin set sail from England aboard the H.M.S. Beagle for a voyage around the world.

End Show 15-1 The Puzzle of Life's Diversity Slide 4 of 20 Copyright Pearson Prentice Hall Voyage of the Beagle During his travels, Darwin made numerous observations and collected evidence that led him to propose a hypothesis about the way life changes over time. That hypothesis has become the theory of evolution (aka theory of natural selection).

End Show 15-1 The Puzzle of Life's Diversity Slide 5 of 20 Copyright Pearson Prentice Hall Darwin's Observations He observed many plants and animals were well suited to the environments they inhabited. He was impressed by the ways in which organisms survived and produced offspring. Darwin was puzzled by where different species lived and did not live.

End Show 15-1 The Puzzle of Life's Diversity Slide 6 of 20 Copyright Pearson Prentice Hall Darwin's Observations Living Organisms and Fossils Darwin collected the preserved remains of ancient organisms, called fossils. Some of those fossils resembled organisms that were still alive. Others looked completely unlike any creature he had ever seen.

End Show 15-1 The Puzzle of Life's Diversity Slide 7 of 20 Copyright Pearson Prentice Hall Darwin's Observations The Galápagos Islands Darwin observed that the Galápagos Islands were close together but had very different climates.

End Show 15-1 The Puzzle of Life's Diversity Slide 8 of 20 Copyright Pearson Prentice Hall The Journey Home Darwin observed that the characteristics of many animals and plants varied noticeably among the different islands of the Galápagos.

End Show 15-1 The Puzzle of Life's Diversity Slide 9 of 20 Copyright Pearson Prentice Hall The Journey Home Darwin wondered if animals living on different islands had once been members of the same species. These separate species would have evolved from an original South American ancestor species.

End Show 15-1 The Puzzle of Life's Diversity Slide 10 of 20 An Ancient, Changing Earth Hutton and Lyell helped scientists recognize that Earth is many millions of years old, and the processes that changed Earth in the past are the same processes that operate in the present

End Show 15-1 The Puzzle of Life's Diversity Slide 11 of 20 Copyright Pearson Prentice Hall An Ancient, Changing Earth This understanding of geology influenced Darwin: If the Earth could change over time, life might change as well. It would have taken many years for life to change in the way Lyell suggested. This would have been possible only if the Earth were extremely old.

End Show 15-1 The Puzzle of Life's Diversity Slide 12 of 20 Copyright Pearson Prentice Hall Lamarck's Evolution Hypotheses Jean-Baptiste Lamarck recognized that: living things have changed over time. all species were descended from other species. organisms were adapted to their environments.

End Show 15-1 The Puzzle of Life's Diversity Slide 13 of 20 Copyright Pearson Prentice Hall Lamarck's Evolution Hypotheses Lamarck proposed that by selective use or disuse of organs, organisms acquired or lost certain traits during their lifetime. These traits could then be passed on to their offspring. Over time, this process led to change in a species.

End Show 15-1 The Puzzle of Life's Diversity Slide 14 of 20 Copyright Pearson Prentice Hall Lamarck's Evolution Hypotheses Lamarck's Hypothesis A male fiddler crab uses its front claw to ward off predators and to attract mates.

End Show 15-1 The Puzzle of Life's Diversity Slide 15 of 20 Copyright Pearson Prentice Hall Lamarck's Evolution Hypotheses Lamarck's Hypothesis Because the front claw is used repeatedly, it becomes larger. This characteristic (large claw) is passed onto its offspring.

End Show 15-1 The Puzzle of Life's Diversity Slide 16 of 20 Copyright Pearson Prentice Hall Lamarck's Evolution Hypotheses Evaluating Lamarck's Hypotheses Lamarck’s hypotheses of evolution are incorrect in several ways. Lamarck did not know: how traits are inherited. that an organism’s behavior has no effect on its heritable characteristics. However, he paved the way for the work of later biologists.

End Show 15-1 The Puzzle of Life's Diversity Slide 17 of 20 Copyright Pearson Prentice Hall Publication of On the Origin of Species In 1859, Darwin published his book, On the Origin of Species. proposed a mechanism for evolution called natural selection. presented evidence that evolution has been taking place for millions of years—and continues in all living things.

End Show 15-1 The Puzzle of Life's Diversity Slide 18 of 20 Copyright Pearson Prentice Hall Inherited Variation and Artificial Selection Darwin noted that plant and animal breeders would breed only the largest hogs, the fastest horses, or the cows that produced the most milk. Darwin termed this process artificial selection. Artificial selection is the selection by humans for breeding of useful traits from the natural variation among different organisms.

End Show 15-1 The Puzzle of Life's Diversity Slide 19 of 20 Copyright Pearson Prentice Hall Evolution by Natural Selection Survival of the Fittest The ability of an individual to survive and reproduce in its specific environment is fitness. Darwin proposed that fitness is the result of adaptations. An adaptation is any inherited characteristic that increases an organism's chance of survival.

End Show 15-1 The Puzzle of Life's Diversity Slide 20 of 20 Copyright Pearson Prentice Hall Evolution by Natural Selection Because of its similarities to artificial selection, Darwin referred to the survival of the fittest as natural selection. In natural selection, the traits being selected contribute to an organism's fitness in its environment.

End Show 15-1 The Puzzle of Life's Diversity Slide 21 of 20 Copyright Pearson Prentice Hall Evolution by Natural Selection Over time, natural selection results in changes in the inherited characteristics of a population. These changes increase a species' fitness in its environment. Each living species has descended, with changes, from other species over time. Darwin referred to this principle as descent with modification.

End Show 15-1 The Puzzle of Life's Diversity Slide 22 of 20 Copyright Pearson Prentice Hall Evidence of Evolution Darwin argued that living things have been evolving on Earth for millions of years. Evidence for this process include: the fossil record geographical distribution homologous structures similarities in early development, or embryology.

End Show 15-1 The Puzzle of Life's Diversity Slide 23 of 20 Copyright Pearson Prentice Hall Evidence of Evolution The Fossil Record Darwin saw fossils as a record of the history of life on Earth. By comparing fossils from older rock layers with fossils from younger layers, scientists could document that life on Earth has changed over time.

End Show 15-1 The Puzzle of Life's Diversity Slide 24 of 20 Copyright Pearson Prentice Hall

End Show 15-1 The Puzzle of Life's Diversity Slide 25 of 20 Copyright Pearson Prentice Hall Evidence of Evolution Geographical Distribution Similar, But Unrelated Species an d

End Show 15-1 The Puzzle of Life's Diversity Slide 26 of 20 Copyright Pearson Prentice Hall Evidence of Evolution Homologous Body Structures Structures that have different mature forms but develop from the same embryonic tissues are called homologous structures.

End Show 15-1 The Puzzle of Life's Diversity Slide 27 of 20 Copyright Pearson Prentice Hall

End Show 15-1 The Puzzle of Life's Diversity Slide 28 of 20 Copyright Pearson Prentice Hall Evidence of Evolution Not all homologous structures serve important functions. The organs of many animals are so reduced in size that they are just vestiges, or traces, of homologous organs in other species. These organs are called vestigial organs.

End Show 15-1 The Puzzle of Life's Diversity Slide 29 of 20 Copyright Pearson Prentice Hall Evidence of Evolution Similarities in Embryology The early stages, or embryos, of many animals with backbones are very similar. The same groups of embryonic cells develop in the same order and in similar patterns to produce the tissues and organs of all vertebrates. Chick embryo (LM) Human embryo Pharyngeal pouches Post-anal tail