Homologous
I chose to compare Whales and Snakes for Homologous traits because they both came from early tetrapods (4-legged creatures). They are also completely polar opposites in size which I thought made a fun comparison. Admittedly these might too far apart to count because they don't currently possess the same trait, but they did at one point.
While whales obviously do not have four limbs, research has shown that they actually DID at one time and eventually lost their two smaller hind legs adapting to life exclusively in water. Whales still technically have traces of a pelvis and at times (although rarely) are born with vestiges of hind legs.
Snakes, on the other hand, have no legs but research suggests that some, if not all, actually did at one point. It is believed that they eventually stopped growing them because it potentially destroyed some form of movement such as burrowing into the earth.
Analogous
I've tried to find the common ancestor of of these two groups and it's like going down a rabbit hole! I just can't seem to figure it out. :(
Had to think about your homologous pairing a little. The trait that you are comparing here is the absence of limbs. Now, the residual limbs that both possess (in the pelvis, I believe) are indeed homologous since they were inherited by a common ancestor. But the trait of lost limbs is a trait that evolved independently in both species. That makes this trait analogous in these two species. In order for it to be homologous, they would have had to have inherited this lack of limbs from a common ancestor, which they didn't. Does that make sense?
ReplyDeleteGood description on the analogs, and they are indeed analogs. It isn't necessary to know who the ancestor was. It is necessary to (a) understand that they did have one and (b) regardless of whether or not it had wings, you need to know that at least one of these species (namely the bird) developed wings independently from that ancestor. That means these are analogs. Birds developed wings after (or during) their split from reptiles.
"That makes this trait analogous in these two species. In order for it to be homologous, they would have had to have inherited this lack of limbs from a common ancestor, which they didn't. Does that make sense?"
ReplyDeleteTotally! :)
:-) Good!
DeleteHi Genesis!
ReplyDeleteInteresting choice on picking whales and snakes as an example of homologous trait! I liked how you compared the species for both homologous traits and analogous traits. I thought it was interesting how at one point in time, whales had limbs. I also thought it was pretty cool how whales lost their smaller hind legs in order to adjust and fit in its environment. I honestly did not know that before. Really enjoyed reading your blog!
-Warunee Kamolrat