Homologous: It is easier to see visually, if you take the image of the Bat and the Human, that these animals have two different adaptations. The bat uses its forelimb for flight and we use our arm in a completely different manner (i.e. pick things up).Humans and bats are two different animals visually however, both fit under the category of vertebrates. The structure that is passed on here is the skeletons of the two animals. All vertebrates have skeletons because their ancestors had skeletons and passed the trait (i.e. the bat still visually shows all five digits just as the human limb does.)  Both the Human and the bat are in the class of Mammals, this alone suggests that the two are related; also, mammals are practically identical at the pre-embryonic stage, if the two were not of an ancestral relation they would not exhibit this trait either. This (somewhat) proves that bats and humans come from common ancestry. We know that the ancestor had to have possessed these traits (vertebrae) in order to have passed it on, or it would have looked more analogous in nature as opposed to a deviation of an identical vertebral trait. Humans and bats, as well as many other mammals have the same forearms with the exact same bones just with an alteration in function. If they were not homologous ancestors they would not share this same trait, let alone have the same forearm bones. The exact answer to what ancestor they both have in common is unknown to me but through some research some have said a “tree shrew”. According to how our book breaks this down, they are simply very distant cousins of one another.

   

Analogous: One could look at a bird and a butterfly for describing an analogous trait as the two both share the feature of flight and yet are not ancestors of one another in the definition of passing on this trait genetically. Insect wings lack bones rather use fluid pressure or some other mechanism to move the wing and allow for flight. The bird has the same bones of a forearm and the qualities of mammals in the structure of bones, which allow for the movement of its wings. Insects tend to have four sets of wings where as a bird only has a single set. The wings of the butterfly are scale like in nature and the wings of the bird have feathers; yet both are adapted to their environment through the use of flight. In this respect both have solved the need to get off the ground in the same way. Although the bird wings do look superficially similar to that of the butterfly the anatomical make up is totally different. The traits are Analogous because there is no known ancestral history.

-Maria Hernandez