Week 3 Analogy/ Homology Assignment
- A)
Humans and whales have a similar homologous bone structure in
the arm. Whales and humans have a humorous, radius, ulna, carpals,
metacarpals, and phalanges these bones make up our arms as well
as a whale's flippers.
B)The
homologous trait is the bone structure of both organisms in the arms. The arms
of humans are very different from whales because we evolved from an ancestor
who lived in trees and needed longer forearms to help them climb while whales
have the same bones but their structure is shorter in terms of the forearm and suited for
only water where they use their flippers to help them maneuver through
the water. These homologous traits exert differences because they live in two
polar opposite environments. Humans live on land so we rely more heavily
on our arms to pick things up while whales live only in the water so they need
to use their flippers to help them maneuver their big bodies through
the water.
C) Since humans and
whales are considered mammals I think that the common ancestor has to be an
animal that spent most of its time on land. The ancestor would have to be
a land animal because it was firstly a mammal and plus only mammals have the
same bone structures.
D)
- A)
I think two species who are totally different but are characterized close
has to be the platypus and the duck. Both species have bills and
lay eggs but the difference is that the platypus is a mammal and the duck
is a bird.
B) The analogous traits
of both species are the bill, the webbed feet, and the ability to lay eggs. The
platypus and duck both have webbed feet in order to help them swim. They also
both have bills but the platypus uses its bill as like an extension of an electric
field in order to catch prey. They both also lay eggs which is uncommon for a
mammal. Even though these species are similar they are two totally
different species.
C) I think that the
platypus has a common relative to the duck . In my opinion, I
believe that there was a divergence between a mammal and a bird in order to
have an organism who is able to lay eggs and yet still be considered a mammal.
D)
Hello Brian,
ReplyDeleteIt is definitely interesting to think about how a whale and human have incredibly similar bone structures, yet one is a sea mammal, and we use our arms for lifting, for example, rather than to move, or more specifically, to help steer themselves. However, I would say that it is more likely that the common ancestor was from the water and then came on land, because as evolution shows(or is thought to show, it is a theory after all) that the fin or flipper came before primates and then humans. And the closeness of the duck and platypus is a very interesting thought. The platypus is likely an animal that split from the line that became primates early on, at least that is my guess. Although, if the duck and platypus were to have a close(ish) related ancestor, that would likely make them more homologous rather then analogous, however that is probably not the case.
Hey Brian,
ReplyDeleteReading your post about the comparison between whales and humans was really unique and different. I did not think about comparing a human to an animal but it makes sense because we did evolve from from similar species, and the fact that we are grouped together as mammals solidifies your facts. On the other hand, I was a little confused with your comparison between the platypus and the duck. What about the structure of the bill or the webbed feet makes them analogous and not homologous? I guess I would just like to hear some more clarification from you! Overall, good job and you images do a great job of comparing the species.
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ReplyDeleteThe opening section was an opportunity to describe the species themselves, not just the traits, which was intended for the second section. Give your reader more background on your chosen pair.
ReplyDeleteGood description of the functional differences in the forelimbs and how this translated into structural differences. It might have been helpful to include a discussion of the differences in the skeletal structure as well, as this is how we can track the differences through the fossil record.
"Since humans and whales are considered mammals I think that the common ancestor has to be an animal that spent most of its time on land. "
You didn't take that where I expected it to go. Remember that there are lots of terrestrial animals who are not mammals (birds, reptiles, amphibians and lots and lots of insects and arthropods). The logical jump here would be to say that because both organisms are mammals, their common ancestor would also have been a mammal, though you are correct that it was a terrestrial mammal. We know from fossil evidence that the common mammalian ancestor possessed the primitive structure and passed that trait onto these two descendants with variation arising due to different environments and functions. That is what we need to know to confirm that these are homologous traits.
Good choice of species for your analogous species, but it would have been better to stick with one trait instead of wandering off into several. In the ancestry section, we need to have a discussion on whether the chosen traits are actually analogous... which one are you discussing? They can't be treated as a whole.
Some traits are easier to compare than others as they appear in the fossil record. For example, the bills of the platypus and the duck are both made of hard keratin which can be preserved on occasion. It is more difficult for eggs to be fossilized and nearly impossible for webbing, so let's stick with the bills.
What you are arguing in your section on ancestry would actually support these traits as homologs, not analogs. Careful about relying upon "belief". Just look for what the evidence tells you.
We know the following, with regard to ancestry. Ducks are birds, who arose from reptiles. Likewise, the platypus is a mammal, who also arose from reptiles, so the common ancestor would be an archaic reptile. The question is, when did the bills evolve? If they arose from that common reptilian ancestor, then there is a chance these traits are homologous. If the bill arose independently in at least one species, these traits are analogous.
In both the platypus and the duck, bill structures arise after they split off of their primary groups (mammals and birds, respectively) and moved into their aquatic environments, i.e., long after that split from the common reptilian ancestor. This is what we need to know to confirm that these traits are indeed analogous.
Good images.