Thursday, January 26, 2012

Homologous Structures and their Evolution

So for my first post, I originally wanted to post about the earliest signs of appendages and found that that post may be a bit long. (Appendages exist at the cellular level and even though I love cellular biology I didn't feel like reading papers today. ha) So I decided to do it another time.

I remembered that in class we looked at the figure of the different forelimb structures in mammals, and saw that they were homologous. Now for those of you reading this blog that are not from my class, homologous is defined by Mariam-Webster Dictionary as "having the same relative structure." A link to the dictionary entry can be found at the bottom of this post.

So from this we can derive that the homologous limbs in mammals are those that have similar bone structure.

So the question I had was how did these changes in function occur? We know that all mammals had a common ancestor? But what did that ancestor look like. The Canadian MUSEUM of nature states that "one of the earliest mammals was the shrew like animal shrew-like Morganucodon." The have a really cool video that shows the diversification of limbs over the centuries as mammals evolved, but also hows they maintained the same general structure. The video takes the mammal phylogeny and follows the the tree from the Morganucodon to modern day humans, bats, and whale, and shows some of the forms limbs took along the journey of evolution.

The interactive video can be found at:

Wednesday, January 18, 2012

Hi everyone!

I talked with the professor today after class to seek his opinion about the themes I sent out earlier. He really liked the evolution of appendages idea. We felt that there is a lot of material there for everyone. You don't have to stick to humans, in fact, it'd be great if we covered many organisms and/or compared appendages of different organisms. Such as the evolution of a rat's tail vs. that of a kangaroo? Or the evolution of external vs. internal sex organs. Or vestigial appendages, such as the tailbone/coccyx in humans (I call that one :). He doesn't have a problem with overlap in the course, but he just wants us to do our own in-depth research about the topic. He also thought the evolution of pathogens would be acceptable as well, but he liked the evolution of appedages much better.

Just food for thought! See you on Friday!