1. Frog & Rabbit
a. A frog and a rabbit; they look totally different and have different skin, colors and eat different things but they have homologous traits when it comes to their forelimbs and certain bones in their bodies.
b. They have very similar functions when it comes to their forelimbs and how it developed because a frog uses their limbs as much as a rabbit, except that some frogs jump higher and faster distances then rabbits. This is due to their prey being quicker then a rabbits prey. We can see that a frog has longer forelimbs, hands, legs, and fingers because it uses and lives off of them and its tongue. It needs these long and sticky hands along with long fingers to stick onto the trees and leaves of its habitat. A rabbit has smaller forelimbs and bigger legs for fast rapid movements; a very fast hop instead of high jumps. A rabbit usually has bigger prey and bigger teeth to chew it down with as well.
c. Generally the common ancestor of these two would have been a fish with homologous structures which went on to land and then evolved by its needs and environment around it. A lizard could have also been a possible ancestor but could have also came from a fish long ago. They all have similar forelimbs as a homologous trait and all evolved differently due to their placement or adaptation.
d. 
2. Shark Fin and Dolphin Flipper
a. Both the Shark and the Dolphin live in the sea and both seem to be very similar in structure because of their color shape and size. However they are not quite similar when it comes to ancestry or common descendant.
b. They may have just developed similarly due to being in a similar environment. They have similar fins except the dolphin has a flipper and their is a difference in bone structure there. The dolphins use their flippers quite more often the the shark uses his fin. The dolphin needs its flippers to due the long jumps it does in and out of the sea. sharks just need the fins to swim same traits different attributes.
c. First off the dolphin is a mammal so it is probably more closely related to another animal; rather then the shark which is a fish. So in this case we cannot say they had a common descent. We know that these traits are analogous because not only is the bone structure different in their fins/flippers but one one of these animals is a fish the other is considered a mammal still so they obviously evolved looking so alike because they both were raised up in the sea.
d. 
Okay on your opening description, but couldn't this apply to any two organisms? Could this be a little more specific for you chosen pair?
ReplyDeleteThe guidelines ask that you focus on one trait in particular. You seem to wander between the forelimb and the teeth and tongue. I'll stick with the first discussed trait, the forelimb. If you consider the skeletal and general limb structure, the traits are definitely homologous, since the common ancestor (archaic amphibians) possessed the ancestral limb structure. Just make sure you understand that you need to address traits that are shared by common descent and can be demonstrated as such.
You don't need to go back to fish to find a common ancestor, and this wouldn't help you anyway, since the common ancestor needs to actually possess the ancestral form of the trait in question, correct? Do fish possess that early form of the forelimb? Make sure you understand what is required in terms of ancestry to confirm that these are homologs.
Again, a little more specifics for your opening description for your analogous pairing.
Good explanation of your analogous structures.
"So in this case we cannot say they had a common descent."
Let's clarify this. If you understand who the common ancestor actually was, namely an archic cartilangenous fish, you will see that the shark DID inherit its fin structure from this common ancestor. So couldn't this be a homologous trait? That is where the dolphin comes in. We know that dolphins evolved their fins after their mammalian ancestors moved into the aquatic environment, long, long after the split with the common ancestor with the sharks. That means dolphin fins did evolve independently from that common ancestor, even if sharks didn't. That is sufficient to confirm that these are analogous traits.
Good images.