Analogy/Homology Blog Post
Humans and monkeys have similar homologous traits. A
monkey's tail and the human tail bone, or coccyx, are examples of homologous
structures. Humans and monkeys developed from a common ancestor that had a
tail, but while monkeys kept the structure as they evolved, humans did not.
The Chimpanzee is a common ancestor to both the human and the monkey. Chimpanzees do not have tails. They are not
like other primates such as the Monkey species; they are more like the Ape, and the Gorilla, which doesn't have a tail.
Dolphins are mammals
and sharks are related more heavily to fish, but the two share several
structures with shared functions between the two species. Dolphin and shark
dorsal fins and body shape are some analogous traits that are shared between
both species. Even though they look very similar I was not able to find any
common ancestors and believed it happened thru convergent evolution.
You start off with the comparison between apes and monkeys, which is fine. You end up listing nearly all the apes in your discussion. Understand that it would have been acceptable to compare all apes in general to all monkeys in general with regard to this trait.
ReplyDeleteCorrect, humans (and all apes) are lacking in a tail, while monkey's have one. This *describes* the differences in traits but it doesn't explain why the differences are there. Admittedly, scientists are still arguing over why apes lost their tail, but a discussion of the existing debate should at least been included to offer your reader a full picture of this homologous pairing. Furthermore, do apes really have no tail? Or is it just greatly reduced? And does the remnant have no function at all? Expand.
It is included in your earlier paragraph, but you are correct that the primitive (or ancestral) version of this trait is the presence of the full length tail. Good job not falling for the trap of saying that apes evolved from monkeys but from a common ancestor of both.
Good description of the analogous traits but you needed to explain how these traits arose in response to shared environmental pressures, namely the aquatic environment. Not just structure was needed but function as well.
Correct, these trait arose from convergent evolution but a little thought could have walked you backward in time to help you come up with the ancestral evidence to confirm this.
The common ancestor of these two organisms was an archic cartilangenous fish, which actually means that the shark DID inherit its fin structure from this common ancestor. So couldn't this be a homologous trait? That is where the dolphin comes in. We know that dolphins evolved their fins after their mammalian ancestors moved into the aquatic environment, long, long after the split with the common ancestor with the sharks. That means dolphin fins did evolve independently from that common ancestor, even if sharks didn't. That is sufficient to confirm that these are analogous traits.
Good images.