1B. Each of these species have a forelimb but they look different and they each use them very differently to. For example, a frogs forelimb is short and stubby and they use it to swim and jump and push themselves forward and to also eat and bring food to its mouth. A rabbit is small and skinny and hey use their forelimb to hold themselves up, run, hop and sleep. The forelimb is different in both of the species because of the size of the animal its self and the size of the actual animal and its functions.
1C. The common ancestor of these two species could possibly be the human because our arms posses a similar setup as the frogs and rabbits with multiple bones in the forelimb. Also the arm of a human has a much different skeletal setup compared with the legs and the same goes for a frogs arms and legs.
2B. Snakes have evolved to burrow and eventually became smooth-scaled and developed eye coverings to avoid injury to their eyes while diggings and they ultimately lost their limbs leaving them with a body similar to the worm. Snakes do not have eye so they can see or sense something is coming using by its vibrations. Worms do not have eyes either but they have light receptors and can tell when they are in the dark or the light.
2C. I do not think that the common ancestor could have possessed the analogous trait because the snake adapted into its body shape it has now. These traits are analogous and not genetically related because the snake and the worm have different functions of their bodies and they are not identical at all meaning their traits could not have come from something or someone.
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 identification of the species or 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. Needed to be expanded.
ReplyDeleteHomology: For the second section, you do make connections between function and structure and the different environments. Understand that relative size is not an issue here. The *shape* is generally the important issue here.
"The common ancestor of these two species could possibly be the human "
That's not how genetic common ancestry works. We are modern species, not ancestral. This is like arguing that a distant cousin, several times removed, living on the other side of the country, is your ancestor.
So how do we confirm homology via ancestry? Rabbits are mammals, who arose from reptiles, who arose from amphibians. Since frogs are also amphibians, the common ancestor was an archaic amphibian who DID possess the skeletal limb structure in question. This is what we needed to know to confirm the common genetic origin of a homologous trait.
Analogy: Just for clarity, it is the strategy of avoiding eye damage that is the trait in comparison, correct? In worms, the strategy is to get rid of eyes and in snakes, it is a structure that protects the eye. We need to specify that it is the "strategy" that is the trait in question here since technically worms don't even have eyes to protect, correct? Otherwise, good description here and good connection between similarities in structure and function.
"the snake and the worm have different functions of their bodies"
But that wouldn't confirm analogy of THIS trait. You can't use the analogy in one trait to assume analogy in another. You have to treat them independently. So how do we know this strategy is analogous?
I'm not familiar with worm evolution, so I'm afraid I can't speak to that, but we do know quite a lot about snake evolution and suspect that there is likely evidence that this trait arose independently in snakes, but that evidence needed to be provided here. This isn't the type of trait that will fossilize, so we would need genetic/phylogenetic evidence. Did you find any information here on evolution of this structure in snakes that would support your claim here?
Good images.
Wow! I also did a homology between two species regarding their forelimbs. When researching did you find out that the makeup of their forelimb - the ulna, radius, and humerus - is what makes them a homology? After this assignment I started looking at animals differently. I would never have expected a rabbit and a frog to have a common ancestor. Thank you for the read!
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ReplyDeleteI really like your post specifically about the worm and the snake. I honestly have compared the two species before or even thought about their similarities. It is interesting to see two species that look so similar, yet have no ancestral link. I also think the images are clear and give a good comparison between the species. Also, for the frog and bunny section, did you discover how similar the bone structures were between the two animals. I think that the comparison between the bones in the animals is extremely interesting. Anyways, great post!
Very interesting, I also found that the Humerus, Radius, and Ulna are the bones in forelimbs that contribute to making them Homologous traits. However, I don't really think that a human could possibly be a common ancestor of these two species, as humans live in modern day, and are primates with a completely different setup in their bone structures in regards to the Radius,Ulna, and Humerus. Since these two species aren't even part of the say Class, their common ancestor is going to be very very far back, and probably looks nothing like either of these species. Overall an interesting post, and good choice of animals for your blog question.
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