For the analogous example I would like to take a look at fish and penguins. Fish breathe and live under water while penguins also go in the water but primarily live on land. The analogous trait that they both posses is their fins. They do have similar structure as they are both located on the sides of the animals. The reason both species possess this trait is because it was the best feature that was functional in each environment, not because the trait came from a common ancestor. However, it is true that all species do share a common ancestor. If we go back far enough I do believe that the common ancestor we find for these two species will also possess the analogous trait of having fins. The reason we know that these traits are analogous is became the two species do not possess the same trait as a result of common descent.
Your opening description on your homologous trait could have been expanded to provide greater detail and clarity.
ReplyDelete"The reason the homologous trait exhibits so much difference between the two species is because they do share a common ancestor, but that common ancestor is very distant."
Actually, distance doesn't have much to do with it. The reason they have structural differences is due to different environmental pressures.
How do you know that these are shared genetic traits instead of independently evolved structures? What is their skeletal structures like? Can you speculate as to who the common ancestor might have been? Did that common ancestor possess this trait? We need to know that in order to confirm these are homologs. All species share a common ancestor if you go back far enough. That doesn't mean that all of their traits are homologous.
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Better description of your analogous trait.
"If we go back far enough I do believe that the common ancestor we find for these two species will also possess the analogous trait of having fins."
But wouldn't that mean that this trait is homologous? Is it possible for the common ancestor to have the trait and have the trait arise independently in at least one of the organisms? What do we know about bird wing evolution that helps us recognized that the fin of the penquin is a derived, independently evolved trait which confirms that these are indeed analogs?
good choice for homologous traitsbut maybe could of be a little more detailed or specific about on how they shared those traits..
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