Week 3: Analogy/Homology Blog Post
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For your homologus traits provide the following information (25 pts):
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Briefly describe the two different species that possess the homologus trait. (5 pts)
- Two different species that possess the homologous trait are: An ape, the arm being the homologous structure, and a human, with the arm being the homologous structure also.
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Describe the homologus trait of each species, focusing on the differences in structure and
function of the trait. Why do these homologus traits exhibit differences between the two
species? Make sure your explanation is clear and complete. (10 pts)
The homologous trait of these two would be the arm. They differ in structure because of evolution and how they are intended to be used.
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Who was (generally, not specifically) the common ancestor of these two species and how do
you know that ancestor possessed this homologous trait? (5 pts)
The common ancestor of the two are african apes.
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Provide an image of each species in this comparison. (5 pts)
pandathumb3.gif
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Briefly describe the two different species that possess the homologus trait. (5 pts)
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For your analogous traits provide the following information (25 pts):
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Briefly describe the two different species that possess the analogous trait. (5 pts)
Two species that possess the analogous trait are: a shark and a dolphin. The analogous structure would be their fin.
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Describe the analogous trait of each species, focusing on the similarities in structure and
function of the trait. Clearly explain why these analogous traits exhibit similarities between
the two species. (10 pts)
the analogous structure of the fin is similar on both the shark and the dolphin. They are similar and both serve the function of stability.
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All pairs of organisms share some common ancestor if you go back far enough in time. Could
the common ancestor of these two species have possessed this analogous trait? How do we
know these traits are analogous and not genetically related from common descent? (5 pts) We know they are analogous because they do not share the same ancestor.
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Provide an image of each species in this comparison. (5 pts)
sharkordolphintxt1.png
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Briefly describe the two different species that possess the analogous trait. (5 pts)
With regard to your homologous pairing, complications arise when you are comparing "apes" and "humans". Humans ARE apes, so you need to be more specific in your selection. Are you comparing humans and chimpanzees? Gorillas? Orangutans?
ReplyDeleteYes, human forelimbs are distinctly different than (let's say) gorilla forelimbs. How specifically do they differ in structure and function? And how can you explain these differences in terms of their different environments? How do gorillas use their forearms differently from humans and how do you see that in their structure? You've stated that a homologous traits exist but haven't gone any further to support that claim.
African apes include the chimpanzee and the gorilla. These are both modern species of apes, just as humans are, and you can't speak of modern species being the ancestors of modern species. That's like saying your cousin is your ancestor. It doesn't work. Regardless, we don't need to be that specific. Humans and other non-human apes (such as gorillas, chimpanzees and orangutans) share a common archaic ape ancestor that possessed the ancestral forelimb structure, passing that structure down to these modern descendents. Think of a family tree.
Images need to be inserted using the image function in Blogger. There are instructions on the "Help" page of the course blog.
Good choice of analogous traits. Can you explain why this trait helps in the shared environmental pressures of these two organisms? Stability in what medium? Expand.
As stated in the guidelines, all organism have a common ancestor if you go back far enough, these two organisms included. The common ancestor of sharks and dolphins was actually an archaic fish who, ironically, shared this fin structure and passed it onto its shark descendent (who is also a fish). Does that mean this is a homologous structure? No, because we also know that dolphins developed their fin structure after they split off from land mammals and adapted to the water environment. That means their fins arose independently, long after that split from the common ancestor. That is all we need to know to confirm these are analogous traits.
Don't be afraid to expand these posts. Make sure you are explaining concepts and points completely, addressing all guideline requirements fully. If you have questions or if some things are confusing, you should email me before the assignment is due to help clarify misconceptions.