week 3 Analogy/Homology
Analogy/HomologyAnalogous Traits: Similar traits between organism such as birds
butterflies with wings and able to fly yet have no common evolutionary descent.
Homologous Traits: two or more different species that are similar that come from a common ancestor.
They could have the similarities in bone structure, DNA sequences or anatomical structures.
Homologs
Human and bird forearms , these organisms even though the bird can fly and the human body can not fly they are very similar (bird, Human) every forearm bone is similar, such as the.... Humerus, radius, Ulna, Carpals, Metacarpals and Phalange. Humans are covered with skin as birds are covered with feathers. Humans use their forearms to pick up things, swing a bat, while Birds use their forearms to fly. Common ancestor is the reptile.
Analogy
A bee and a bat would be Analogous species. A bee being an insect and a bat being a mammal, yet both have wings that are used for flying. A bee's wing has a fore wing and a hind wing where as a bat has the same bones has a human's forearm, upper arm bone, lower arm bone, wrist bones, metacarpals and fingers. They have separate evolutionary origins, yet both can fly.
They did inherit forelimbs from a common ancestor.
posted by five primates @ January 14, 2018
4 Comments
4 Comments:
Both comparisons you chose for each trait were very interesting. As stated the bird wing and human forearm have very similar bone structure. The birds ancestor does trace back to a reptile that became a dinosaur then a bird. The humans ancestor is a ancient mammal. In your analogous comparison you did a good example showing that although the wings function is the same but both come from different ancestor. Great post!
I really found your first choice rather interesting for the homologous trait. The human to bird forearms, while similar in bone structure are not anything similar in looks or views. I think it is crazy that we could share traits to that of an aviary but hey... SCIENCE!
Thanks for sharing man!
It is better to follow the prompts in the guidelines for these posts to make sure your responses to each prompt is clear and you get the appropriate credit.
Good description of analogous traits. Homologous traits are genetically related traits that have evolved functional/structural differences due to different environmental pressures.
The opening prompt for both sections specifically ask for descriptions, not just identifications or description of the traits, of your two species. Expand and provide your readers with a better foundation of understanding for these comparisons.
It is important to be very specific about what traits you are comparing in your homologous traits. The wing structure is a derived trait of birds and not possessed by the common ancestor with humans. That means the wing is not a homologous trait. What IS homologous is the skeletal structure of these limbs, and that is what you needed to compare here. You mention the bones but you don't explain how they have changed in humans and birds to produce their different limb structure. Those were the differences we needed here. You do post an image of those skeletal differences, but images should support your claim, not replace it.
Regarding ancestry: Yes, the common ancestor would have been an archaic reptile... but how does this confirm that these traits are homologs? We know from fossil record that early reptiles possessed the skeletal structure in question here and passed it onto these two descendant species. That's what we need to know to confirm that these are homologous traits, arising via common descent.
RE: Analogous traits.
Okay on your description of your analogous trait and discussion on similarities in function and structure.
"They did inherit forelimbs from a common ancestor."
Technically, the wing of a bee is not a "forelimb". That is only referring to the front limbs of a tetrapod. But this aside, wouldn't this claim then indicate that these traits arose via common ancestry... which would mean that these traits WEREN'T analogies? We need to confirm that these traits arose independently to confirm analogy. How do we do that?
It is difficult to guess at what the common ancestor of the bird and butterfly looked like some 100's of millions of years ago... it may have possessed wings or it may not have, but fortunately, we don't need to know that to confirm that these traits are analogous. While it is possible that the butterfly inherited its wings from that common ancestor, what about the bird? We know quite a bit about bird and bird-wing evolution. Birds evolved wings as they split from reptiles, and this occurred long, long after the split with that common ancestor with the butterfly. This means bird wing evolution occurred independently from that common ancestor with the butterfly. That is sufficient to confirm that these are not the product of common descent and are indeed analogous.
Good images.
Thanks so much for the comparison between the bat and the bee; very interesting. I especially appreciate the note about fore wings vs hind wings; something I had not considered previously. Thanks!
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