Human Arm and Owl Wing
1.
Humans or also referred to as homo sapiens, more developed of all the mammals.
An owl is a nocturnal bird known for their big forward facing eyes and hooded beak.
Humans have a longer ulna and radius, while an owl, or birds in general have longer carpals & meta carpals. The trait from both species exhibit differences simply because they are used for different functions/ purposes.
Humans need a larger ulna and radius for upper body & hand/arm strength which is essential to their survival in their environment. Birds however need longer carpals and metacarpals to support their feathers and fly which is essential to their travel and eating as well.
A common ancestor of these two species would be probably a fish from prehistoric times. Its homologous because all the species that came from that ancestor have the same bones.
Analogous Trait:
Butterfly & Chicken
2.
Butterfly is an insect with two pairs of large wings that are covered with tiny scales, usually brightly colored.
Butterflies and chickens both have wings however the wings are different in structure and function.
The wings of birds have bones, muscles and feathers while the wings of butterflies are made of veins, protein and scales.
Although a chicken is a bird and has wings, it does not mean their direct function is for flying like most other birds or a butterfly in this case.
Its analogous because of the fact that nothing in the structure of both kind of wings are similar.
I dont think a common ancestor would possess this trait.
Hey George!
ReplyDeleteI really liked the examples you used in your post! I thought you did a great job and understood the assignment completely.
"Humans or also referred to as homo sapiens, more developed of all the mammals. "
ReplyDeleteNo... :-) We like to think so, but hopefully you will understand by the end of the class that we have developed differently, but not necessarily "more developed". We can't brachiate like gibbons or run like gazelles or hold our breath like blue whales. Are they "more developed" than we are in those areas? It is all a matter of relativity. Make sure you aren't speaking from an anthropocentric bias. We aren't better... we have just evolved differently from all other organisms but you can say the same thing about every other organism.
Otherwise okay on your description and good explanation of the key differences in the human and owl forelimb.
Do you really have to go all the way back to the fish to find a common ancestor? And isn't that common ancestor supposed to have the trait if these are homologies? Humans are mammals and owls are birds. Both arose from reptiles, so the common ancestor would have been an archaic reptile, who did indeed have the ancestral limb structure. We know that from fossil records, so this confirms both common ancestry and homology.
I am given the impression in your next section that you have misconceptions about what defines analogous traits. Analogy isn't defined by a complete lack of similarities in the traits in question. Analogy is defined by similarities in structure and function that are due to common descent, but to convergent evolution.
So what are the similarities in chicken and butterfly wing structure. Since chickens don't really fly well, this is actually a difficult comparison to make and a different bird choice would have been better perhaps to have to organism with trait with similar functions.
Ancestry on this is a little difficult because the common ancestor of these two organisms would have lived 100's of millions of years ago. But we do know quite a bit about bird wing evolution. Bird wings arose as they split from reptiles, long, long after the split with that common ancestor with the butterfly. So even if that common ancestor had wings and passed them onto the butterfly (which is possible), we know that bird wings later arose independently of this. That is all we need to know to confirm that these traits did NOT arise from common descent.
Review this concept and email me with any questions.
Good images.