a) Two animals I am going to compare today are the Whale and Dolphin.
The whale and dolphin are both aquatic mammals that give birth to live young, have warm blood, flippers, a full bony skeleton and lungs.
b) Both these animals possess flippers, however, whales like the orca whale have larger bodies and larger flippers for more power, while dolphins are built more for speed so they are more slender.
c) Both these animals had a common ancestor that was a land dwelling creature, the Pakicetus. Over time it evolved to swim in water.
a) Two animals I am comparing are the dolphin and shark.
b) Each species has flippers, although sharks are not as opposable as that of a dolphin's. Both are used to help maneuver in the water. The shark's pectoral fin (front flipper) is made of cartilage but resembles the bones inside the front fin of the dolphin. They are not related however because the shark is a fish with gills and the dolphin has lungs and a blow hole.
c) Because the dolphin and whale come from a mammal and the shark is more closely related to fish it would have to go back several mya to where mammals were evolving from the first land dwelling creatures from the sea. These traits are analogous because of the different origins of the species. Sharks started out in the water long before whales and dolphins have, as they are aquatic mammals and not fish.
Okay on your opening description.
ReplyDeleteHow do we know that the differences in traits that you describe is actually due to actual difference in function instead of just due to difference in body size? The paw of a Chihuahua and paw of a St. Bernard are different in size, but not because they have different functions. They are just attached to different sized bodies and must be different in size because of that. How is your example different from that?
It is often difficult to find clear examples of homologs in organisms that are very closely related. It might have helped identifying shared structures in more distantly related individuals to make sure the function was clearly different.
You didn't need to be too precise on ancestry, but the problem here is that the common ancestor was actually a likely aquatic mammal, not terrestrial. In all likelihood, the ancestor did indeed possess the fin structure. We still need to understand the difference in function, however.
For your analogy, the opening section asked that you describe your species, not just identify them.
Okay on your description of the analogous traits. Just for clarification, the shark fin is indeed cartilagenous but is not patterned after the skeletal structure in the dolphin.
With regard to ancestry, you are correct on your identification of recent ancestry, but if you go back far enough, they do share a common ancestor. The common ancestor of the dolphin and shark is an archaic fish, who did possess these fin structures and also passed that trait onto extant shark species. So the question is, did the dolphin also inherit it's fin from that common ancestor? Dolphins "fins" evolved after dolphins split off from terrestrial mammals, i.e., long after the split with ancient fish. This provides us with the evidence we need to confirm that this trait did evolve independently in at least one of these organisms, making these traits analogous.
Good images.
Hi Emily,
ReplyDeleteI very much enjoyed reading about the animals you choose. I wanted to do my blog originally on dolphins and whales as well but I had a hard time finding an animal to use for analogous traits. I had a rather difficult time understanding and writing on this topic, but I found that your blog post helped me to make sense of what homologous and analogous traits are. I like you pictures and the easy to red way you did this assignment.
Hello Emily, great post. I have never seen your blog, I really like your background.
ReplyDeleteThe dolphin and the whale defenetly have common ancestor because they are very similar in there shape and almost everything else.You found great analogous trait. The land crater looks very similar to a dog.Is it possible that a dog can also have the same ancestor?