b. In humans, the homologous trait being discussed is the tail bone, which is the located near the rectum in terms of its exterior location in the human anatomy. The tail bone, officially known as coccyx, is a useless bone in terms of function, but it is a sign that humans have evolved over the years from an ancestor that had a tail. Contrastingly, some primates possess tails where our tail bones are located, and these tails are an essential part of their lives and how they function. Over time, the lack of a need for a tail led humans to evolve so that they do not have tails, which in turn has left the coccyx as the only remnants of the tails that our ancestors once had. In contrast, other primates like monkeys still have tails because they need to use them to survive on a daily basis because of the environments they live in. Humans have evolved away from tails because of lack of necessity.
c. The common ancestor shared between humans and monkeys (and similar primates) is a type of primate that lived before humans existed. These two groups are within the same species of mammal, so their last closest link is fairly recent when compared to other animals with shared homologous traits.
d. Refer to pictures below
2. a. An example of an analogous trait would be fins, which exist on fish such as sharks as well as birds like penguins. These fins, which serve the same universal purpose, are not necessarily linked because the two species are related to one another directly.
b. The fins on birds like penguins allow the birds to move from place to place on icy surfaces, as they have to slide to travel and these fins increase their ability to do so. Fish use their fins to swim through water, so in this way both species use their fins as means of transformation. Both penguins and fish have these fins as their arms, meaning that they are vital to their survival in their respective environments.
c. I could not find a species that traced back to the relationship between penguins and fish, but evidently the species had to have had fins and obviously lived in a water environment.
d. Refer to picture
Valid homologous comparison, but it might have been helpful to choose two specific organisms to allow for a clearer comparison. Comparing across large groups like that make it difficult to identify specific functional/structural differences.
ReplyDeleteThe loss of the tail is actually a derived trait of apes in general, so this is a trait humans share with all greater and lessor apes. The tail bone is not completely functionless but still serves as an important attachment point for muscles, which is why we still have it, even in it's rudimentary form. But why did we lose the rest of the tail? You mention that we didn't need it, but why not? What is the difference between apes and other primates (and mammals and reptiles and amphibians and birds and fish) that would make it advantageous to lose that tail?
Good description on your analogous traits.
"I could not find a species that traced back to the relationship between penguins and fish, but evidently the species had to have had fins and obviously lived in a water environment."
Ah, but that's not what we need in order for these to be analogs. Yes, if you go far back enough (early fish) you find a common ancestor, and yes that ancestor (as a fish) had fins, but did that trait get passed down to both organisms, the penguin and the fish? If so, that would make these shared traits, not analogs. But we do know that penguin "fins" are derived traits from bird wings, so they arose independently from the common ancestor. They weren't directly inherited. That is what makes them analogous.
Make sure you understand the issue of ancestry for these concepts.
Good images.
Ah yes, the human tail, the cool missing appendage that we wish we had--along with an extra set of arms. One question you leave up in the air is the importance of the loss of our tails. What functions do tails serve in general that we no longer have a need for? As a final note on the subject, humans aren't unique in their lack of tails, gorillas and orangutans also don't have tails.
ReplyDeleteInteresting analogs, you subverted the professor's rule to not use her example of a penguin's wings by comparing it to fish fins instead! Sneaky and creative, I like it. :P The functionality makes sense to me, and fish are totally not modern dinosaurs in which I would assume that they are analogs as well. Just to be safe though, be sure to look over the professor's post to be clear about the difference between analog and homolog. I can attest to the confusion between the two, so I played it safe and compared a plant and a frog. :)
Totally irrelevant question: why are out bottoms called our bottom if they are located towards out middle?
I have also wondered what it would be like to have a tail. I think it would be an interesting experience but I have a hard time thinking of a way that a tail would be useful. My best guess is that the tail could be used for better balance, which I definitely could use.
ReplyDeleteIn terms of the analog, I tend to think that the penguins ancestor moved back into the water and developed the fins because it gave a better chance of survival. Even though fins were a trait of the common ancestor, I believe the penguins had to redevelop the fins after they were lost in subsequent land animal species.