Analogy and homology are perhaps the concepts which seem to be easier to exemplify than to define. when different species are structurally compared, certain features can be described as either analogous or homologous. for example, flight requires certain rigid aeronautical principles of design, yet birds, bats, and insects (5) have all conquered the air. the wings of all three types of animals derive from different embryological structures, but they perform the same functions. in this case, the flight organs of these creatures can be said to be analogous. in contrast, features that arise from the same structures in the embryo but are used in different functions are said to be homologous. the pectoral fins of a fish, the wings of a bird, and the (10) forelimbs of a mammal are all homologous structures. they are genetically related in the sense that both the forelimb and the wing evolved from the fin.