B) The bones in both of these animals, are basically the same bones. The bones in the human arm are going to be a different size from the bones in a whales front fins. They both serve for a function even though they are a slightly different function. The whale swims and the human uses their arms for everyday activities and to grab things. There are different things that could be made better or perfect in the human arm or whale fin but the structure that they have, is perfect for there species. They only need to compete for greatness amongst each other, not other species. A whale fin would not do any good on a human body and same goes for a whale to have the human arm structure because it would not be as great for swimming.
C) As it is said, the ape is the common ancestor of the early human species. The ape was also the first species to possess "hand" structures. At that point in time, the apes used their arms and hands to walk on, where as today, the human uses them for a different purpose.
A) Two animals that posses analogous traits would be a spider and a elephant leg. Both have "legs" but both species are from different origins. The legs of both species are also used for different purposes and work differently.
B) Spiders are from the insect species and elephants are from the mammal species. The legs of a spider are jointed leg segments and are called podomeires where as the elephants legs are composed of bones that are jointed together with ligaments. The legs of a elephant rotate in the socket as they walk. Elephants also apply power independently to each leg as compared to other animals applying power to their rear legs to drive them.
C) I think the ancestors of the first insects did not have legs where as the first ancestors of mammals, did have legs. I think that enviromental pressure caused spiders to have legs to coupe with the pressures and get them to move around faster.
When you mentioned that a human and a whale have homologous traits I found that very hard to believe. You can’t really see the bone structures of a whale’s fin unlike a human’s hand. But once I saw the diagram that you posted it made sense. I didn't realize their fin had such bone structure in it. Great observation!
ReplyDeleteI had no idea either until I started doing research and working on this project!
ReplyDeleteHi Amberlyn,
ReplyDeleteI have to say that I really liked this assignment because it forces us to think outside the box and your post did that for me. To think that the human arm is similar to a whales fin is amazing, but after reading your post I can totally see how the two are related and it is amazing to think how far we have evolved as well as the world as a whole. Great Post.
Good basic background information on the homologous trait. Be careful about declaring structures "perfect" for a particular species. You be amazed with how many structural weaknesses we have in our anatomy. We are not perfect by any means, but you are correct that the structure we have serves us better than the structure of a whale!
ReplyDeleteWhen I speak of a "common ancestor", I'm speaking of the common ancestor between whales and humans, which is an early mammal. Regardless of the specific ancestor, it possessed the similar limb structure that humans and whales inherited, so these are definitely homologs.
Apes are not the first to evolve the hand structure. Early monkeys developed it first.
I have never had a student compare an elephant and a spider leg before! Yes, the jointed limb is an analogous trait in this instance. Again, the common ancestor we speak of is one between the elephant and the spider, which is a little hard to wrap our heads arounds since it was likely 100's of millions of years ago, but regardless, the legs of the elephant evolved through parallel evolution, not through inheritance from that common ancestor.