Chapter 13: Mutual Affinities of Organic Beings: Morphology: Embryology: Rudimentary Organs Summary and Analysis

Biologists classify organisms into various groups of resemblance that gradually get smaller and include fewer organisms. Thus, the organisms that belong to the same family resemble one another in some way, but not nearly as much as the organisms that belong to the same genus or even species resemble one another. These classifications are not as straightforward as simply identifying one group that walks on land, another which flies, and so on. Rather, the creatures within the various classifications often differ from one another dramatically in certain habits, while retaining other certain common characteristics. The theory of natural selection can make sense of this organization as a kind of outline of the history of the species. Those organisms that belong to the same...