Darwin makes useful organs that are adapted for certain purposes and atrophied organs that are imperfect both support his argument about natural selection. He starts off the chapter by discussing the classification of species; he argues that by classifying organisms we can learn about their ancestry and analyze their relationship to other organisms. He also explains how biologists characterize species into groups according to their characteristics within a species. The groups become less precise the higher up you go – until there is one large classification group.
Darwin argues that organisms within a species are still subject to variation and they will compete for survival, however because of their variation the extent to which they can manipulate resources also varies. Natural selection will force these organisms to become separate categories over a long period of time because their variation has affected the way they survive. The pattern of classification is analogous to the development of speciation.
Darwin also states that the way biologists classify species depends greatly on ancestry instead of individual creation. He describes homologies which are structures that indicate a shared ancestor: “the framework of bones being the same in the hand of a man, wing of a bird, fin of a porpoise, and leg of the horse – the same number of vertebrae forming the neck of the giraffe and of the elephant…at once explain themselves on the theory of descent with slow and slight successive modifications” (Darwin 391). The structure is similar because the form and pattern are alike. This represents a shared ancestor because the original structure has been modified, which is why it can vary in the way it is used.
Ancestry supports natural selection because it implies that organisms are not individually created; he argues that if God uniquely created organisms than biologists would classify them according to their similarities. Darwin uses the example of whales and fish who share similar characteristics but are not classified together; they look similar because both of their ancestors fought to survive underwater.
Darwin makes the argument that useful organs that are adapted according to certain purposes become closer to developing into the perfect organ through generations of modification. Darwin uses the argument of technological advancement to analogously describe how the telescope has become more advanced due to modified progression. Similarly, natural selection helps organs like the eyeball become increasingly more complex and advanced. Natural selection therefore creates highly complex organs that slowly become more advanced as a species’ continues to develop over generations. Darwin also analyzes the the gaps in organ modifications, which represent an intermediate species that has become extinct; the next generation is able to develop modifications that allow it to survive, unlike its predecessor. Modifications illustrate natural selection because it...