Homology Defined

The term homology refers to biological   structures or characteristics that are similar or the same found on two or   more different species when those characteristics can be traced to a common   ancestor or the species. An example of homology is seen in the forelimbs of   frogs, birds, rabbits, and lizards. Although these limbs have a different   appearance in each species, they all share the same set of bones. This same   arrangement of bones has been identified in fossils of a very old extinct   species, Eusthenopteron, which was inherited by frogs, birds, rabbits, and   lizards.

同源性定义

同源性一词是指在两个或两个以上不同物种上发现的相似或相同的生物结构或特征，同时这些特征可追溯到共同祖先或物种。青蛙、鸟类、兔子和蜥蜴的前肢就是一个同源性器官一个例子。尽管这些肢体在每个物种中都有不同的外观，但它们都有相同的骨骼体系。在一个非常古老的已灭绝物种，即真掌鳍鱼的化石中也发现了同样的骨骼排列，真掌鳍鱼的这套骨骼被青蛙、鸟类、兔子和蜥蜴继承下来。