Analogy/homology blog post
The two different species I chose were the Horses front legs and a humans arms as homologous traits. I found that both contain the humerus, radius and ulna bones. They exhibit differences due to the fact that humans are part of the primates and horses are part of the mammalian class. Humans use muscles and bones together in order to function. However horses' bones are connected which allows the animal to lift its leg as well as run and jump. What connects both of these species is called *Eutheria, a subclass of mammals all of which have a placenta and reach an advanced state of development before birth. ( Which took a lot of digging to find the common ancestor since the two species are from two different classes).
(*Madsci website)
Analogous
The Two species I chose were the webbed feet in ducks and the webbed feet in frogs.
Ducks use their webbing to push water faster, making it easier for them to swim and primarily have more webbing because they are in the water more. Ducks are aves and are not mammals as many people think. Ducks are also warm blooded.
Frogs while some have lots of webbing some have minimal webbing dependent on how much time they spend in the water. Frogs can use their webbing to swim as well as to grasp on to things, catch their food and climb. Frogs are amphibians and cold blooded.
Although no genetic history is shared between these two species they do share this trait. Their is no common ancestor between these two species which make them analogous.
Hey Donielle,
ReplyDeleteFound your work on webbed feet very interesting. I was wondering if birds are dinosaurs, then perhaps the webbing morphology is not as distant as may have been previously thought. I know that some people can have a webbed feet, syndactyly. They don’t know the exact cause, but does appear to have a familial component. I’m not sure if this is “true webbing” in the case of an aquatic harbinger, or simply a malformation that gives the appearance of webbing. Looking through your post caused me to think about all of the different species who share this trait in one form or another. Webbing is something in aquatic animals that just seems so normal that it goes with noticing. Thanks for bringing it to my attention.
Skeletal anatomy comparison of horse and human was also excellent. I have often wondered how common ancestry can be reasonably argued when such a great diversity of function exists with all of the same basic bones. Great post.
Hi Donielle; I really liked your post, it actually helped me when it came down to what i wanted to do mine on lol. I really liked the work you did with the Webbed feet as well, and the extra finger on the frogs foot gives it the better ability to grab things when compared to the ducks foot, this extra appendage might be the reason why they cant swim as fast as ducks. it gave me the idea to look into different animals that might have gills or once had gills and now use different features (such as extended breath holding, etc..), I look forward to your other posts.
ReplyDeleteIn general, good job on your homologous traits. A few clarifications:
ReplyDeleteBoth humans and horses belong to the mammalian class and both use the same connective tissue to hold bones together. The difference is in the structure of the bones. Why do horse have bigger, stronger bones than humans? Why do they only have one toe? Why are their radius and ulna fused and humans are separate? The explanation is in the function, which you touched on briefly in horses. How does it differ from humans and how is this reflected in the skeleton? This would have been a good discussion for this part of your post.
Eutheria is not an ancestor but a grouping of mammals defined as being placental animals. The key here is that both organisms are mammals. Therefore you can conclude that the ancestor was also a mammal who shared the ancestral limb structure and passed it on through common descent.
Good image. It reflects the very different limb structures.
Regarding your analogous trait, as is mentioned in the quidelines, ALL organisms share a common ancestor if you go back far enough. Birds arose from reptiles who arose from amphibians (like frogs), so the common ancestor of these two organisms was an amphibian. The question is, did that common ancestor have webbed feet and pass on the trait to these two descendents?
Well, we know that not all birds have webbed feet. That means it is a derived trait, developed independently from the ancestor of all birds. Since that trait arose independently, we know that the bird webbing and the frog webbing arose separately, not from common descent.
Other than the issue of ancestry, good discussion on the similar function and structure of these traits. It is a good example of an analogous trait.
I never would have made the connection between a horse and human. I had no idea that they had similarities in bone structure. i had trouble finding the correct common ancestors between my animals as well. How can you find a common ancestor?
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