Darwin Presents His Case

15-3 Darwin Presents His Case Slide 2 of 41 End Show 15-3 Darwin Presents His Case Publication of On the Origin of Species Publication of On the Origin of Species He shelved his manuscript for years and told his wife to publish it in case he died. In 1858, Alfred Wallace sent an essay to Darwin for review. Wallace’s ideas summarized Darwin’s work. In 1859, Darwin published his book, On the Origin of Species. Slide 3 of 41 End Show 15-3 Darwin Presents His Case Publication of On the Origin of Species In his book, Darwin: • 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. Slide 4 of 41 End Show 15-3 Darwin Presents His Case Inherited Variation and Artificial Selection Inherited Variation and Artificial Selection Members of each species vary from one another in important ways. 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. Slide 5 of 41 End Show 15-3 Darwin Presents His Case Inherited Variation and Artificial Selection Artificial selection is the selection by humans for breeding of useful traits from the natural variation among different organisms. Slide 6 of 41 End Show 15-3 Darwin Presents His Case Inherited Variation and Artificial Selection Cauliflower Brussels Sprouts Broccoli Kohlrabi Ancestral Species Kale Slide 7 of 41 End Show 15-3 Darwin Presents His Case Evolution by Natural Selection Evolution by Natural Selection Darwin compared processes in nature to artificial selection. By doing so, he developed a scientific hypothesis to explain how evolution occurs. Slide 8 of 41 End Show 15-3 Darwin Presents His Case Evolution by Natural Selection The Struggle for Existence Darwin realized that high birth rates and a shortage of life's basic needs would force organisms to compete for resources. Slide 9 of 41 End Show 15-3 Darwin Presents His Case Evolution by Natural Selection How is natural selection related to a species' fitness? Slide 10 of 41 End Show 15-3 Darwin Presents His Case 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. Slide 11 of 41 End Show 15-3 Darwin Presents His Case 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. Slide 12 of 41 End Show 15-3 Darwin Presents His Case 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. Slide 13 of 41 End Show 15-3 Darwin Presents His Case Evolution by Natural Selection Descent With Modification Natural selection produces organisms that have different structures, establish different niches, or occupy different habitats. Each living species has descended, with changes, from other species over time. Darwin referred to this principle as descent with modification. Slide 14 of 41 End Show 15-3 Darwin Presents His Case Evidence of Evolution What evidence of evolution did Darwin present? Slide 15 of 41 End Show 15-3 Darwin Presents His Case Evidence of Evolution 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. Slide 16 of 41 End Show 15-3 Darwin Presents His Case 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. Slide 17 of 41 End Show 15-3 Darwin Presents His Case Slide 18 of 41 End Show 15-3 Darwin Presents His Case Evidence of Evolution Geographical Distribution Similar, But Unrelated Species and and Slide 19 of 41 End Show 15-3 Darwin Presents His Case Evidence of Evolution Homologous Body Structures Structures that have different mature forms but develop from the same embryonic tissues are called homologous structures. Slide 20 of 41 End Show 15-3 Darwin Presents His Case Evidence of Evolution Homologous Structures Turtle Alligator Bird Mammal Ancient, lobefinned fish Slide 21 of 41 End Show 15-3 Darwin Presents His Case Slide 22 of 41 End Show 15-3 Darwin Presents His Case 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. Slide 23 of 41 End Show 15-3 Darwin Presents His Case Similarities in Embryology Evidence of Evolution 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. Pharyngeal pouches Post-anal tail Chick embryo (LM) Human embryo Slide 24 of 41 End Show 15-3 Darwin Presents His Case Evolutionary Theory Evolutionary Theory Scientific advances in many fields of biology, geology, and physics have confirmed and expanded most of Darwin’s hypotheses. Evolutionary theory continues to change as new data are gathered and new ways of thinking arise. Slide 25 of 41 End Show