Analogy/Homology
1. For the homologous trait provide the following information.
a. Two different species that possess the homologous trait are human beings and monkeys. The tailbone in human beings is a homologous trait, it gets its name "tailbone" due to the fact it is a homologous structure to the beginning of tails. Such as the tails that monkey's have. Human Beings have lost the original function of their tailbone through evolution. Human Beings now have a coccyx, which is very similar to a tail, however the coccyx serves no purpose. Part of this is the fact that Human beings are bipedal, and have no need for a tail. Monkey's on the other hand, are bipedal, yet still use their tails for things such as grasping objects such as branches and food, so their tail still serves a purpose.
b. Monkey's have what is called a prehensile tail. A prehensile tail has adapted to grasp or hold objects, full use of a prehensile tail includes being able to manipulate objects, and aid the monkey in finding and eating food. The human being tail bone is now a vestigial trait that humans no longer have a use for. There are several theories as to why humans only have a tail bone such as, we are bipedal, we don't need a tail to brush away bugs, help our balance or to grab things, so over time there was no need for humans to have a tail. The tailbone is formed of three to five vertebrae, the last piece is a tiny nodule of bone. A monkey's tail is made of vertebrae that are more flexible.
c. Human beings and Monkey's are both primates that descended from a common ape ancestor over six million years ago, we share a common ape ancestor with chimpanzees and chimpanzees are the closest primate relative to humans. Like Human beings, chimpanzees do not have tails. However, the ape species includes humans, monkey's and chimpanzees, so the Ape is our common ancestor.
d.
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2. For your analogous traits provide the following information.
a.The penguin and the fish are examples of species with analogous traits. Penguins and fish both have fin like structures, yet one of these are a bird and one is a fish. Therefore they are not related through ancestors or anything. The main function of a fish is to swim, and they have fins located in different places to help them move through the water, stop, as well as shift left or right, so the fin serves a lot of purpose for a fish. A penguin also uses their fins, for gliding through water. Unlike the fish, the penguin can rotate their fins in different directions, which help their fins act like a paddle. Penguins have fins instead of wings, because a wing would hinder their swimming.
b. Penguins are part of the bird family, they even have feathers like birds do, however the feathers are highly dense and very short. Penguins also lay eggs, and are warm blooded. Over time penguins wings adapted to become fins (flippers), which they use for swimming. Penguins rely on swimming for food, so developing these fins was more important then growing wings to fly. Fish on the other hand are cold blooded and cannot survive on land like penguins do. The fish fin serves many functions, their dorsal fin prevents them from rolling over, their pectoral fin are used for steering. So the fins in both penguins and fish serve entirely different purposes. The one similarity is both use their fins for guidance through the water.
c. Fish were here on earth long before birds were. Amphibians evolved from fish, over 360 million years ago, and then mammals and birds evolved from reptile like ancestors so the common ancestor would be a fish from over 360 million years ago. Fish had fins, so this would be the analogous trait that penguins now have. The fish and the penguin are not related as one is a fish, cold blooded and one is a bird, warm blooded. They are from entirely different species. Penguins and fish are analogous to each other, based upon the structure of their fins. The penguins fin is used to help navigate through the water, ice and snow, and the fish's fin is used to navigate only through water.
d.
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Hi Jodi,
ReplyDeleteI really enjoyed your post. I struggled on mine a bit trying to tie in the information and descriptions. Your post made me see how I could have done it better. I like that each of your sections are thorough and provide a lot of detailed history on each of the organisms you chose. The monkey and the human traits and how they evolved differently was well written. Also, nice job on your choice of photos!
Hello,
ReplyDeleteGreat job on your blog post. The examples you picked, especially the fish and penguin comparison, really helped to highlight the differences between homologous and analogous traits. I though it was interesting that the main use for a monkey's tail is for grasping objects. While I know they are capable of this, I would have guessed their tail's main use would be balance based on how they traverse their environment. I though it was interesting that monkeys are classified as bipeds like humans, I would have guessed they were quadrupeds. Overall, great post.
Interesting that the two parts of your posted are formatted so differently. How did manage that? If you are taking votes, the second part is easier to read but the first is more aesthetically pleasing. :-)
ReplyDeleteHomology: You kind of jump right into the discussion of the trait comparisons, but the opening section in both the homologous and analogous areas asked for a description of your *species*, not just a description of the *traits*. This would help your reader understand the environment and behavior of the species to better understand why their traits evolved the way they did.
Good description of the differences in structure for the tail/tailbone, but careful about the function. Even in its diminutive state, the tailbone still serves as important muscle attachments for our abdominal floor, helping our excretory, urinary and reproductive activities. We would notice if it weren't there.
"Human beings and Monkey's are both primates that descended from a common ape ancestor over six million years ago"
Careful... monkeys can't evolve from apes, as they evolved BEFORE apes did. Moreover, apes (like all humans) have no tail. You need to find the common ancestor who possessed the generalized structure of this trait (the tail) from which modern tailed monkeys and tailless (the derived trait) humans arose. Humans and monkeys are both primates so they arose from an archaic primate, and we know from the fossil record that these early primates possessed the generalized tail structure. That's what we need to know to confirm homology.
Analogy: Same problem in your first section. This was the opportunity to describe the species in general, not just the traits. That trait description belonged in the second section.
Great second section, until this line:
"So the fins in both penguins and fish serve entirely different purposes."
No, the point here is that they serve very *similar* functions. That, along with the absence of common genetic descent, is what makes these traits analogous.
"The fish and the penguin are not related as one is a fish, cold blooded and one is a bird, warm blooded."
I'm puzzled, because you've just walked your reader through the evidence of exactly the opposite conclusion, that they are indeed related through the common ancestor of an archaic fish.
"Penguins and fish are analogous to each other, based upon the structure of their fins. "
Entire species can NOT be analogous. Only their traits can. And two organisms can have some traits that are analogous and others that are homologous. In this case, the fin/wing structures are analogous but the vertebral/skull structures are homologous. Does that make sense?
So how do we use ancestry to confirm analogy here? You aren't far off, but have some misconceptions that lead you astray. The common ancestor of the penguin and fish is an archaic fish, who did possess these fin structure and also passed that trait onto extant fish species. So the question is, did the penguin also inherit it's fin from that common ancestor? As you point out, penguins are birds, but let's take that information further to address this issue. Penguin "fins" are actually derived bird wings. Birds evolved wings when they split off of their reptilian ancestor, 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.