the two species i have chosen are bats and humans; they both possess the homologous trait.
a humans arm and a bats are are homologous to each other simply because of its skeleton structure.
the human arm has the same structure as the bats, because of the similar bones, humans have a humerus(highlighted in purple) and a radius ( highlighted in orange) as you can see in picture below, they both also have 5 bone endings and for the human that would be their fingers. but they both have different tasks, bats are made to fly while humans are not and also bones of a bats are very hallow compared to a humans. a common ancestors to humans would be an ape while a bats common ancestor would be a microchiroptera, believed to be a smaller bat that ate mainly fruits. 
ANALOGOUS TRAITS
the two species i have chosen are platypus and a fish. both have a fin like structure to help them navigate through their environments. And they both have thin bone structures going through their fins, which makes them more useful to paddle through waters. ( as you can see in the images below) over years of evolution both fins/webbing design helped them survive in their environments.the common ancestors of these two animals would be traced back to pre-historic animals ; although we aren't 100% sure scientists believe that platypus would be de decedents of fish. also they could relate to monothenes and marsupials.
Hello Taline,
ReplyDeleteAfter reading the last few chapters of our textbook, I have learned a lot. I would not have guessed that we, as humans, share anything in common with some of the species that we do. However, when I looked at some of the similarities of bone structure and the function of the limbs, it makes sense. Your photo illustrates the bone structure of the similarities that I am talking about. However, the structure seems alike, but the function is very different. I thought that your choice of analogous species proved the point that not all species, even if similar, share a common ancestor.
Hello Taline,
ReplyDeleteNice work! I choose the human arm and the bat wing as homologous traits as well, but I had a difficult time finding their common ancestor. let alone I couldn't find the ancestor for the bat which now I know is the microchiroptera. Thanks for the information.
Yes, humans and bats share similarities in structure of the limb because of common descent. But for these traits to be homologous, they need to serve different functions (and you describe that) and there must be differences in structure that mirror these different functions. So how does the skeletal structure of the human and bad forelimb differ in ways that reflect their different functions.
ReplyDeleteRecognize that homologous traits are only homologous if they arise from common descent. That means the common ancestor of those organisms had to have possessed the ancestral trait and passed it onto both organisms. You identify an ancestor of humans and an ancestor of bats but you don't discuss the common ancestor shared by both. Both humans and bats are mammals, so their common ancestor was an ancestral mammal. Did that ancestral mammal possess the ancestral mammalian limb structure? By definition, yes, it did. Therefore these are homologous traits.
Remember what classifies traits as analogous: They must have similar structures and similar functions but the trait needed to arise independently in at least one of the organisms, i.e., not from common descent.
Okay on your description of the organisms and the traits (though fish don't have bones in their fins).
Correct, if you go back far enough, mammals do have a fish ancestor (and amphibian and reptile). So is that where the platypus got it's fins? We know the fish did inherit them from that ancestor, but we know enough about platypus evolution to know that their foot structure is derived from a mammalian limb structure, not from fish fins. That means they arose independently in the platypus and these are therefore analogous traits.
Humans and Bats are mammals that share similar bone structure. Thats interesting to know that humans and bats share similar limbs, but are for different functions because of flight and wings.
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