What Is Darwin's Idea Of Descent With Modification

Chapter 13
Summary:
Darwin explains the classification system used by naturalists (groups of related species called genera, which are then grouped into families) based on similarities and physical relationships, and how it supports his idea of descent with modification. Many species have similar analogous structures that have evolved to have the same physiological importance but were not inherited characteristics. Therefore external appearances of organisms matter little to descent with modification, and they are not used to categorize species. Rather, species are classified based on embryological evidence and internal structures such as reproductive systems, which clearly show descent with modification. Morphology, which compares structural relationships of organs between species, supports the theory of descent with modification through species’ homologous structures, which have evolved over time from the same basic structure. An example of this is seen in human arms, wings of bats, and front legs of moles, which demonstrates the development of organs across species. Another example of homologous structures is the skull, which shows resemblance to the other vertebrae, demonstrating the development of organs within a species. Embryological development shows how and when species diverged, with the …show more content…
Physical characteristics cannot be used as a way to categorize species because many organisms have the same adaptations, therefore internal structures, homologous structures, embryo development, and rudimentary organs are analyzed to find evolutionary similarities that show the modifications of species over time across species or within species. Darwin uses these observations to refute theology once again and prove his own theory, arguing that both perfections and imperfections in species show slow but constant modification over