Chapter+10

Place your questions and answers for Chapter 10 here.

A: The shape of the human ear, just like most everything talked about in this book, is a product of millions of years of trial and error. Since our ear is made up of three areas, and the middle-inner ear is actually where the process of hearing is formatted into a comprehensible form via vibrations and nerve signals, there has to be a way to get the sound //into// that area. Out outer ear, the visual shape we can see outside of our heads, most likely evolved as to direct sounds into those areas that process sound to help us hear. Our ears on concave and have rounded tops( for the most part). This structure guides the sound waves into our ear, funneling them into the middle and inner ear so that we can trigger nerve signals to the brain, which gets translated into hearing. This is advantageous because it helps focus our hearing and improves the quality of sound we hear( assuming no damage has been with-stained in the other parts of the ear). Since we developed an advantage in hearing, we could hear prey or predators and even eventually learn to communicate. These qualities helped advance us as species and increased our fitness(C. King) A: The stapes comes from the second arch. The stapes is equivalent to the hyomandibula in sharks/fish. Both the hyomandibula and stapes use the facial nerve. The hyomandibula kept getting smaller and smaller until it eventually became the stapes in mammals. The shift occurred once fish evolved into organisms that could walk on land. Our upper jaw is the maxilla. The hyomandibula lost its use due to the changing of the environment and different chewing techniques that were required on land. Eventually, the hyomandibula became the stapes in order to still be functional and beneficial to us. Our upper jaw didn't just go away it evolved into the maxilla--our current upper jaw bone. (T. Gebhart)
 * Q: Although many mammals have external ears, they all differ from each other. Theorize as to why human ears might be shaped the way they are (as opposed to other mammals such as dogs) and why this is advantageous. (I. Perler)**
 * Explain how the stapes came about in humans and other land animals, and how they are helpful to us. What do you think is used to create our upper jaw if it is not the stapes? (J. terHorst)**

Shubin is referring to the Cochlea. The cochlea corresponds most closely with the temporal lobes. (O. Heltman)
 * Q: Shubin describes a snail like structure that lies inside the ear. What is its actual name, and what lobe of the brain (frontal, parietal, temporal, or occipital) does it correspond most closely with? (P. Oakes)**

The typical organisms that have external ears are some amphibians, reptiles, and all mammals. The special thing about mammals is that they have a pinna which is a flap of the external ear. The benefit of having a pinna is not only for decorating your ear, but it can also help with hearing. It helps to funnel sound waves into the ear to be heard better and also helps to localize where a sound may be coming from. (J. Speelman)
 * Q: What types of animals have external ears? Why is this - why is it advantageous? (M. Blanchard)**

The purpose of the gel and the hairs in the inner ear is to be able to sense the ways in which the head is tilted, and how fast the head is accelerating and stopping. This is important in our general awareness in space. When our head is moved in any way, the gel moves, therefore moving the hairs along with it. This is what initiates an impulse sent to the brain, which we then process to know which ways we are moving, etc. (L. Bercz)
 * Q: The inner ear has many different parts that do different things. What is the purpose of the gel and the hairs? (A. Schmidt)**

An example of how our inner ear and eyes are connected is that when you move your head back and forth (which moves the fluid in the inner ear is what lets you know your head is moving), your eyes can still stay fixed on a single spot without extra voluntary effort. Each of the eight muscles in both eyes respond to the movement of your head, which is detected by the inner ear. This is advantageous because it allows you to focus on things even when your head is moving. For example, an animal who is hunting and chasing his prey would need to be able to stay focused on his prey despite the motion of his head. Being able to stay focused will give him a much better chance of catching his prey in the end. (A. Nolan).
 * Q: Give an example of how our inner ear and eyes are connected? Why do you think this is advantageous? (C.Nikolai)**

A: When alcohol enters the body, it is distributed throughout the bloodstream, traveling throughout the circulatory system. One of the places the blood passes by is the inner ear, which controls our sense of balance. When the alcohol from the blood diffuses into the fluid of the inner ear, it changes the density fluid. This sends false signals to the brain on the orientation and position of the head relative to the body, with different portions of the inner ear now floating and sinking compared to normal. The more alcohol is present, the more the density of the fluid is changed (up to a certain point), which helps contribute to the poor sense of balance for drunk people (M. Purdon).
 * Q: Using what you know about the effect of alcoholic drinks on vestibular sense in humans, explain why drunk people have difficulty walking straight. (T. Russell)**

//Pax 6// is responsible for helping to form eyes and //Pax 2// forms ears. Their evolutionary relationship shows when looking at the box jellyfish. Even though jellyfish do not have the //Pax// //6// or //Pax 2// genes, the box jellyfish has several eyes. When looking at their genomes, however, these jellyfish have a gene that has similarities to both //Pax// //6// and //Pax 2.// This means that in more primitive creatures, such as jellyfish, these two genes were actually combined into one gene. This explains why many human birth defects affect not just the eyes or the ears, but both. When one is mutated, both are affected because the two are connected. (C. Sanders)
 * Q: What are the two genes that help to form eyes and ears and why is their relationship important? What would happen if there was a mutation in one or both of these genes? (L. Bentley)**

A: The parts of the ear consist of the outer, middle, and inner ear. Each part of the ear has its own purpose and collectively they combine to allow for more complex actions and increased fitness. The middle ear contains three bones, more than other organisms, which allow us to hear and exclusively hear high frequency noises and sounds. The inner ear contains lots of tubes and sacs of gel. These all play an important part in hearing, some in balance, and knowing which direction your head is tilted. It is a very complex system that needs all three separate parts to carry out the functions humans do today. (M. McKinney)
 * Q: There are three parts of the ear. What are they, and what is the purpose/benifit of having these seprate parts? (A. Gatje)**

A. A tiny coiled snail shell. This is a good comparison because the inner ear is a series of coils and small bones which are wrapped up inside of the ear. (E.Olson)
 * Q: What does Shubin compare the ear to? Why do you think he makes this comparison.? (H. Schwarz)**


 * Q: When looking at Box Jellyfish they have many sets of eye but no Pax 6 gene which typically forms eye it has a mix between the Pax 6 and the Pax 2 gene. This shows that the genes that code for eye and ear developed together. What other body system do you think developed together? (C. Hurst)**

A: Space sickness, similar to motion sickness, is caused by the vestibular system adapting to weightlessness (an imbalance in the inner ear). A possible solution is for astronauts to wear properly pressurized space suits. (A. Gatje)
 * Q: Shubin mentions that space sickness is a very real problem for many astronauts. Describe what happens inside the ear to cause this sickness. What could possibly be a solution to this problem? (R. Heis)**


 * Q: In mammals, our middle ear consists of three bones: malleus, incus and stapes. Compare these bones with their counterparts in the reptilian and amphibian ears, with regard to presence/absence, size and location. How could these changes in ear structure be advantageous for mammals? (N. Sarkar) **

**Q: Shubin compares the ear to a Rube Goldberg contraption, in what ways is this** **comparison** **accurate, and in what ways could it be incorrect?(T. McDaniel)** A: This comparison is accurate because the inner workings of the ear are seemingly a system of interconnected mechanical parts, that elicit kinetic responses from a nearby part, from its own elicited kinetic response, much like the overly-complex mechanical systems that are Rube Goldberg contraptions. This appears to be somewhat incorrect as well, as the system that takes place in order to hear inside the ear works in a neat, sequential system in which part A is close to part B (and so on), whereas a Rube Goldberg contraption usually involves parts which are interacting with each other with no regard to proximity, often amounting to the inventions taking up an unnecessary amount of space. (N. Braun)