The two species I choose for the Homologous Trait is the human arm and a seals flipper. Both are homologues as front limb invertebrates. They have the same bone and muscle structure just in different places. They have the humerus, radius and ulna, carpals, metacarpals, and phalanges. They both have evolved from the same ancestry some time in the past. They do have similarities in structure of course, but are different in function. The seals flipper is used for swimming and the human hand is used for grasping and holding. That makes both of these structures homologous.
An example of an Analogous Trait would be a human eye and an octopuses eye. Both are used for seeing of course but have very different structures. They are also from different ancestry, so they do not met up anywhere down the road. The octopuses eye is said to be superior over a human eye because it does not have a "blind spot". If humans did not have a "blind spot" we would have equal eye structures as octopuses. Also humans and octopuses are far away from each other on the tree of life and we of course live in different habitats and environments.
"Invertabrates" means that they don't have a vertebral column. Did you mean "vertebrates"?
ReplyDeleteGood structural explanation and you did well explaining the functional and environmental differences. Can you speculate as to the common ancestor of humans and seals? Were they mammals? Reptiles? Other? Does this help you explain why these are homologs?
The eye is always a great analogous comparison. You did a good job explaining the structural differences and the functional/environmental commonalities which produced these traits. With regard to ancestry, all organisms share a common ancestor if you go back far enough. The question is, how do we know the eye evolved independently in both species? Your discussion of the different design is a great clue. If they were genetically related, they would share a common structure as well. Because they are structurally different, this is evidence of parallel evolution, not common ancestry.
Great images to support your post.
I would of never guess or even thought seals and humans would share a trait let alone the human arm and a seals flipper. Along with that the fact that an Octopus has no blind spots is pretty cool considering its geographic location in oceans. It is a necessary function and is a strength of the octopus's optical prowess, however we are vulnerable to anything from a crack in the ground to something dropping from the sky, because of our peripheral/ limited vision range. A very beneficial post well done.
ReplyDeleteIt look like you had two great examples. I was surprised from some of the research how much in common us humans have with many other species of the world. Even with your example of the flipper and the human's hand. One function that I think you might have missed is that of swimming. We two use our hands for swimming and we do so my cupping them. The eye examples are cool as well as informative. I was not aware that an octopus had such keen eye vision. It would be cool if we also did not have a blind spot.
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