YIF: Chapter 10

The chapter entitled "Ears" or chapter 10 is about the biology of the human ears and relating the middle ear and inner ear to biological ancestors. Shubin is quick to make the remark that the external ear that we humans have, is a trait that is unique to mammals although some amphibians and reptiles do have a somewhat external ear. The man component of the human ear that has been linked to other ancient organisms is the middle ear, composing of the stapes, malleus, and incus. These three ear bones have been linked to gill arches, the stapes in the second gill arch and the malleus and incus in the first gill arch. Through the brilliant minds of Karl Reichert, Ernst Gaupp, and W. K Gregory the link to fish as well as mammal-like reptiles has been discovered, because the three ear bones found in humans is strongly tied to the anatomy of these organisms. Next Shubin writes about the biology of the inner ear, a topic that fascinated me the most. He talked about how the ear works with the brain and the eyes to determine sound, position or acceleration. What was most fascinating was the part of the ear that is the main component in determining these three things. There is a gel like substance in the ear that is touched by hair cells. When one moves or shifts their body, the gel like substance shifts, and tiny rock like objects on top of this gel exaggerate the shift, causing hair cells to detect the movement and ultimately send signals to the brain. This chapter relates the most to Big Idea #3 and Big Idea #4. Big Idea #3 states Living systems store, retrieve, transmit, and respond to information essential to life processes. It is fairly obvious that the three parts of the ear, the inner, middle, and external ear all work to gather in order to obtain knowledge about the position of the person, their current velocity, and hearing sounds. Big Idea #4 states: Biological systems interact, and these systems and their interactions possess complex properties. And like mentioned before, not only does the three parts of the ear work together, but the ear as a whole works with the eye to get the most accurate information of the current environment that one is in. An essential question that can be formulated based on this chapter would be: How do ancient organisms with no ear at all come to evolve to create complex ear systems?