You've got a Lizard in your Ear

The mammalian skull offers a unique opportunity to discuss evolutionary adaptation and and the difference between homologous and analogous features.  When examining the fossil record, the separation of modern "mammals" is demarcated by a change in joint connecting the mandible to the skull.  Prior to this point the connection was formed by two separate bones, the quadrate and the articular.  In birds and lizards and other non-mammalian genera these bone are separate from the body of the mandible and the cranium.  In mammals, the mandible articulates directly with the temporal bone of the cranium, without any intermediary bones.

Meow?

So, are the quadrate and articticular bones present in mammalian skulls?  In fact these bones are conserved, but they serve a different function in the mammalian skull.  Homologous features are the same physical structure between different taxa.  While the features are morphologically the same, they may preform different functions in different organisms.  On the other hand, analogous features have the same functional uses, but arise from different anatomical structures.  In mammals, the incus and the maleus bones of the ear are homologous to the quadrate and articular, respectively.  Although the bones are the same anatomical structure, in mammals, the bones preform a major role in hearing rather than jaw movement.  Instead, the articulation between the temporal and the mandible is analogous to the quadrate/ articular connection in non-mammals, since it has taken on the functional job of connecting the mandible to the cranium.

Transitional fossils have been found showing organisms with a jaw articulation between the temporal and mandible as well as the quadrate and articular.  The change in the jaw articulation is likely due to several different factors.  First of all, reduction in size of the articular and quadrate made them more sensitive to vibrations and improved the hearing capabilities of these organisms.  Organisms with better hearing were better able to avoid predators and reproduce.  Thus, the continued reduction of the ear bones was adaptively advantageous.  Alternatively, the reduction of the jaw joint limited the size of the jaw and the bite strength of the organism.  In this case, a larger joint was more advantageous because it allowed the organism to consume larger prey and also subdue the prey more efficiently.  Thus, decoupling these two functions, allowed mammals to benefit from both increased hearing and jaw size.

Be Aware, It's a Bear!!!

If life ever gets you down, just remember, you have a tiny little lizard jaw joint working in your ear. :)

Digital Telephone: Round 1 Recap

I'm sure most people have have at some point in time played the game telephone.  If not it, it starts with one person coming up with a message and whispering it to the person next to him.  That person then passes it on to the next person and so forth until it reaches the final person.  Usually the message the final person receives is so garbled that it very different from the original.  This exercise is often used to show how rumors change as they are passed from person to person and the importance of returning to the original source of information rather than relying on others interpretation of its meaning.  Digital telephone follows a similar premiss, except instead of whispering the message to the next player, the starting message is transmitted by alternating drawings and written sentences. 

START

1. A big bottle with a squirrel inside fell from the back of a truck.

2. A squirrel in a red bottle fell off the truck.

3. As a pickup truck containing three large glass bottles sped down an empty road, a fourth bottle fell out and shattered, while a fifth bottle containing a trapped squirrel flew through the air.

4. It's a truck going the wrong way down a road into the sunset dropping jars of lizards.

5. Green monsters from the Sun in zip-lock bags descend on Earth's highway system, causing massive traffic congestion and car wrecks.

6. Alien bag-lunches attacking rush hour traffic.

7. Having been angered by the Timmy's lack of recycling, the fireproof brown paper bags
signaled their mother-ship to send backup and enact 'Operation: Destroy Henley Street
Bridge', much to the dismay of the local Knoxvillians who saw no good reason for the brown paper bags' actions and lined up for miles to fight the angry bags valiantly, but ultimately in vain.

END

As you can see, the final sentence is not even close to the original : A big bottle with a squirrel inside fell from the back of a truck. 

But interestingly, if you trace the progression of the game back through the previous sentences and images you can see how little changes in wording or interpretations of what was going on in a picture led to the changes picked up and noted by the next interpreter.  Some people try to describe every detail of an image while others give a broad overview. 

In some ways, digital telephone can be used as an interesting parallel to evolution.  Descent with modification and change over time.  Variation in the drawings forces the writers to select certain aspects to describe.  The chosen aspects are those that appear most significant or important in conveying the original message (adaptive advantage).  Unfortunately since these later authors were not familiar with the original message changes or mutation in the meaning occurs.  Though at the same time some of the basic underlying structures remain.  As you can see, vehicles are represented throughout the course of this game of digital telephone.  In this game only a single line of descent is observed, but what if multiple different people were asked to describe the 3rd image or the 4th image.  I can imaging multiple different interpretations providing different branches and subsequent sentence and image interpretation.

I realize this analogy isn't perfect since the descriptions are being written by an outside observer rather than change due to an actual advantage convey be a specific characteristic, but it is still entertaining to examine the modification and transformation of the information based on the interpretation of each separate contributor.  Also, found this progression very amusing and I hope that you enjoy it as well.

I was reminded of round 1 of digital telephone because currently round 2 is underway and I just finished my drawing for it.  Here it is!!!

Can you guess original sentence I was interpreting?