- A) Two different Species that share homologous traits are humans and chickens. B) A homologous trait that they share is gills. The similarity is noticed in the embryo stage of both species and they share the gill trait with a common ancestor. Most likely the gills serve as a function in development. This homologous trait exhibits differences in structure between humans and chickens because of different environmental pressures. C) The common ancestor of the two species is fish and it’s evident that fish possess gills because they have them now.
- A) Two different species that share analogous traits are penguins and fish. B) The analogous trait that they share is fins. The fins are located in a similar place on each species and share the same function, they help with swimming. This analogous trait exhibits similarities between the two species because they share a marine environment. C) If you go far enough back in time a common ancestor of penguins and fish could have possessed fins. We know this trait is analogous because of the differences between the two species. One has fur, the other has scales; penguins have beaks and fish have teeth, and so on…
Thursday, September 11, 2014
Homologous and Analogous species
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I never knew that humans or chickens have gills in development, that is really interesting! I wonder how humans evolved to only have them in the development stages or if it has been that way since the beginning of evolution. Do you think that means humans and chickens used to live in water? Or, do they not possess any other trait that could prove this?
ReplyDeleteHey CJ,
ReplyDeleteI really enjoyed reading your post. It was very informative and interesting. I was amazed to know that the Chickens and humans share homologous traits. It is very interesting that they have similarity in the embryo stage. The picture you provide about the similarity of chicken and human's embryo explains a lot. Second part of the blog was good too. I learned about penguins and fish. They have so much things in common such as fins are located in the same place and both used the fins for swimming. Overall, great post.
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ReplyDeleteThis is an interesting comparison, but since this appears in both in the developmental stage only, the function is the same in both... a step along the stage to birth or hatching. These are not "gills". That is what they develop into in fish. These are call "branchial arches" at this developmental stage and eventually become, in humans, the tiny bones in the inner ear, the hyoid, and the cartilage and the musculature of the throat and jaw. It develops into similar structures in the chicken (and other birds) but the structure itself is not homologous... it is just a shared developmental structure common in all fish, reptiles, amphibians, mammals and birds. Perhaps an alternative approach would have been to compare the human limb and the bird limb. Those two structures are homologous.
ReplyDeleteIt isn't necessary to go all the way back to early fish to find a common ancestor of these two organisms. Both mammals and birds arose from their reptilian common ancestor.
Good analogous example and you do a good job of explaining why they are similar. It is tempting to think that because these two species are so different, the traits must not be related, but there are homologous structures in fish and birds (such as the gills and the inner ear bones!), in spite of their many differences, so you can't base your argument on that. We do know that these are analogous because we know about how bird evolved. The penguin "fin" is a derived structure that evolved from the bird wing. It was not inherited directly from that early fish common ancestor, but arose independently. That is what makes these structure analogous.
I really like the comparison you used for the homologous trait, I learned a lot from that and I wouldn't have thought humans and chickens have anything in common. Using their development stage to compare a trait is very interesting! Good comparison of analogous traits too. I like that you explained the commonalities between them, but why they are not homologous.
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