There are numerous examples for homology. In fact all vertebrates can be considered as the result of evolution from the same organism type. Even though the extension process may have been similar different species evolved from this ancestor. In many cases the differences can be linked to different extension processes.

Figure 3: Homology                                                  Figure 4: Analogy

There are many examples in nature for homology. Here two distinct partial structures lead to similar forms and function. The extension processes may be very similar, and yet clearly different. Examples of such extensions would be the wolf and the marsupial wolf, which evolved independently from two distinct ancestors, and yet show striking similarities in size, anatomy and behaviour.