The Bones in a human arm are homologous to the bones in the front fins of a whale. The bones in each are basically the same structure, but each serve a very different function.
A human arm has two larger bones leading down to the wrist and fingers (phalanges). Humans use their arms for countless tasks, from sports and communicating, to eating and working with tools, as well as many other things. A whales arm is similar to a humans in the fact that it has two larger bones leading down to five smaller bones that look similar to human fingers. However, a whale uses its fins for navigating its way through the ocean. With these appendages whales can propel themselves through the water as well as use their fins to turn side to side, or up and down.
The traits between humans and whales are similar because they share a common ancestor. Both humans and whales are placental mammals, this means that the mothers nourish their babies through the placenta before they are born. Scientists have created an image of what this possible ancient placental mammal might have looked like. You may notice that is possesses a similar arm structure to humans and whales. While this reconstruction is not exactly what this creature may have looked like, scientists know certain traits this creature had to possess to be related to both humans and whales; one of these traits was the structure of the arm bones.
An example of an analogous shared trait is the wings of a butterfly and the wings of a dove. Both of the animals have wings but did not evolve them from a common ancestor.
The wings of both species allow give them the ability to fly. The traits seem so similar because they both do the same job, allowing the creature to fly from place to place eating food and gathering other resources. So even though the wings of both animals are similar it is not due to a common ancestor, it is because of convergent evolution.
Doves and Butterflies both evolved from separate ancestors without wings. I was not able to find a shared common ancestor in my research. However I was able to find out that doves evolved from a reptile without wings, and butterflies evolved from an arthropod without wings. This means that the ancestors of these species did not share this analogous trait.
Great discussion on your homologous traits. Good explanation on the ancestor and how this supports your claim that these two traits are homologous.
ReplyDeleteYou would have to go back 100's of millions of year to find the common ancestor for the butterfly and bird. All organisms share a common ancestor if you go back far enough, but you are correct that you don't have to located that common ancestor to determine whether wings are an analogous trait in these two organisms. If you can demonstrate that at least one organism developed wings independently of the other (which you have), this is evidence that these are analogous traits.
Well done.
Hello Cody, your post was amazing and got me to understand the subject better because i was a bit confused. Your description about homologus trait and analogous traits were clear. It is crazy how whales and humans have the same structure of the bones! The butterfly and the dove explanation of analogous trait was very interesting as well. good job :)
ReplyDeleteHey Cody, I love the explanation especially because you expand beyond and explain that the bones with construct the human arm can be traced as homologous to many other species as well. Do you think that the perhaps the butterfly could have developed wings to go from flower to flower faster to feed? Maybe the dove needed some speed to escape predators or reach high fruits? Enjoyed the analysis, great job, really learned a lot from this.
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