The concepts of analogy and homology are probably 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 principal of design, yet birds, bats, and insects 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 fight organs of theses creatures can be said to be analogous. The pactoral fins of a fish, the wings of a birds, and the forelimbs of a mammal are all homologous structures. They are genetically related in the sense that both the forelimb and the wings evolved from the fin
