Chapter+07

Place your questions and answers for Chapter 7 here. A: Bodies did not arise sooner in history because of the lack of oxygen in the atmosphere. Oxygen was not very prevalent in ancient times because there was not large amount os photosynthesizing bacteria or even plants at that point to put oxygen into the atmosphere. (C.Nikolai)
 * Q: Why didn't the origin of bodies arise sooner in the timeline of evolution? Based off of the answer to the previous question, why was this certain thing not very prevalent in early times? (T. Gebhart).**

A: Multicellular organism require more energy because the need things like a transportation system to send signals and nutrients to other cells in the organism to survive, if the organism gets complex enough it with even develop organ systems requiring more energy to process organs like the stomach or the heart. The addition of aerobic respiration helps to relieve this problem because it is able to produce much more ATP from a single molecule of glucose. (C.Hurst)
 * Q: One of the impacts of possessing a multicellular body is increased energy consumption. Using only what you know, make a conjecture on why multicellular organisms would need more energy than a like number of single cellular organisms. How would the addition of aerobic respiration help relieve this problem? (M. Purdon)**

A: The analogy Shubin used was that a skeleton compares to a bridge. What this means is that a skeleton's strength depends on its size and shape, but also depends on the anatomy of the bones itself. I agree with this analogy, because humans are just as fragile as bridges, and if our bones are strong then our skeleton will naturally, like a bridge, be strengthened. (H. Schwarz)
 * Q: Explain the analogy Shubin uses to talk about the skeleton and how it works symbolically. Do you agree with his assessment or do you feel as if the analogy, while symbolically probable, is inaccurate(C.King)?**

A: Cells communicate with each other using "words" that are actually molecules that move from one cell to another, sending information to the other cell. Communication is necessary because cells need to know when to divide, when to make molecules, and when to die, so communication between cells helps them to know when to do these things. The cell membrane is semi-permeable, and can have receptors on the outside of the membrane. These characteristics allow for some communicating molecules to pass through the membrane and into the cell towards the nucleus. The receptors on the outside allow for a molecule to be "captured," which causes a chain of reaction of molecular events that travels from the membrane all the way to the nucleus of the cell. (J. terHorst)
 * Q: How do cells communicate with each other, and why would communication be necessary between cells? Use your previous knowledge of the cell membrane to supplement Shubin's explanation of this process. (A. Nolan)**

A: Cells will communicate with each other by sending molecules back and fourth. Without any communication between the cells, they wouldn't know when to divide from each other or when to create new molecules. One cell will send a molecule to attach itself to the outside of the membrane of another cell that will be receiving the signal. Once the molecule is all attached it will send off a chain reaction that passes through the membrane and goes all the way through to the other cell. This is possible because the cell membrane is semi-permeable and will allow the messages to travel through into the cell. (A. Schmidt)

A: Teeth are a hard organ found in the mouth, and they owe their hardness to a high proportion of hydroxyapatite within the enamel the purpose of breaking pieces smaller. The proportion of collagen and and hydroxyapatite in teeth and bones act as a differentiation, as well as their function within the body, as teeth act as a breaking factor, and bones provide structure and blood cells. Collagen acts as a filler between cells, to develop a substance that is resistant to tension. Teeth have little collagen, bone has more, and cartilage has the most, illustrated by all of these parts variability in pliability. (M. Blanchard)
 * Q: Thinking back to our discussion in class about the classification of teeth... using the information from the book, what are teeth? How are teeth different from bone? and finally, why is collagen such a distinguishing factor between bone, teeth, and cartilage? (E. Olson)**

A: Cells communicate by sending molecules back and forth to each other. These molecules then attach to the outer surface of the cell and allow it to understand what is happening in its surroundings. This includes how many other cells there are, what level of nutrients are around, or if there is some kind of foreign invader near the cell. The importance of communication is not lost when an adult is fully grown. The cells still communicate with each other and signal what is going on in the rest of the body. If anything, communication increases due to the overall amount of cells within the body increasing as the body grows. Communication is such a major part of development because it allows cells to work with each other to create something. Cells were no longer working by themselves and only doing things for the individual cells. Communication allows them to become a unified unit and to work together to create even more complex systems such as tissues, organs, and organ systems. Without communication, much of the body we are so familiar with today wouldn't be possible. (L.Bentley)
 * Q: Throughout the chapter, Shubin discusses cellular communication. How do cells communicate?**
 * Once an adult is fully grown, does communication ever lose its importance? W****hy is communication such a major part of development? (C. Sanders)**

A: The first creature with many cells, or bodies persay, showed up aver 500,000 years ago. Two of the scientists who found the oldest fossils of bodies were Martin Gurich and Reginald Springg, however then man who really brought it all together was one by the name of Martin Glaessner. The benifits of having many cells include being have a cell die, yet the organism live on, be able to move more efficiently, create organisms that can actually think, and so much more. (E. Bach)
 * Q: How many years ago were the first creatures with many cells populating the earth and who were some of the scientist credited with discovering these fossils? These colonies were not just colonies, so what are the benefits to having many cells? (J. Speelman)**

A: Shubin considers bodies to be "expensive" because although having a body, and especially a larger body, allows an organism to avoid predators, eat other animals, and move longer distances, it does also require more energy to maintain, and the larger and more collagen containing a body is, the more oxygen it needs for synthesis. I feel as if this idea of expensive may still apply to modern society if you are to tweak it a bit. Though humans especially don't have to worry about being big to avoid predators, this idea of being larger can be applied to one's power in society and ranking (similar to the big male dominance seen in animals). The more powerful someone is, the easier it is for them to live, but also the harder it is for them to maintain their position. (I. Perler)
 * Q: In this chapter, Shubin mentions that in the history of life, there is a moment for everything and maybe the world was not ready for bodies. Considering this, why does Shubin believe that bodies are "expensive?" Moving forward in time, do you think his idea of "expensive" is still applicable or has it too evolved, especially in today's modern consumer** **culture? (O. Heltman)**

A: He found that after a while, the disaggregated cells came together and aggregated again. They first just formed balls, then more organized and pattern shapes, and finally an entirely new sponge body. This experiment demonstrated how more complex sponges were than people had originally thought. Not only did they have bodies, but they also shared the cell adhesion, communication, and scaffolding apparatus that humans had. It showed how effective the sponge's cells were in communicating, and how they formed a whole new body essentially from scratch. It also demonstrated hie different cells in different places do different things. (N. Sarkar)
 * Q: In this chapter, shrubin describes an experiment done by H. V. P. Wilson involving sponges. In this experiment he broke apart the sponges into a set of "disaggerated" cells. Describe the results of this experiment, and explain why they were important to understanding how cells communicate. (E. Bach)**

A: Twisting and side to side movement cause the bone to weaken because the tensile tie is broken just like it would in concrete. (A. Schmidt)
 * Q: Shubin goes into detail about the one of the main materials that give bone its strength -- Hydroxyapatite. Based on the properties of Hydroxyapatite similar to those of concrete, what type movement/activity may cause the bone to weaken? (L.Bercz)**

A: No, this glue is not likely to different among different organisms because of the development of said "glue" before the development of many body-having organisms. However, less complex, body-less organisms like bacteria use quorum sensing to communicate with each other while more complex organisms use said "glue." (T. Russell)
 * Q: In this chapter, Shubin talks about the biological glue that holds our cells together. Would that "glue" differ among different organisms, and if so, how? What makes it different in creatures like us as opposed to less complex organisms? (M. McKinney)**

A: According to Shubin, the Pre-Cambrian Period is the era that contains the oldest known fossils of organisms with bodies. This period occurred roughly 600 million years ago. During this period, the majority of organisms were believed to be eukaryotes such algae. However, with Glaessner's discovery, it is now known that there were very primitive examples of organisms with the first bodies in this period as well. (R.Heis) A: The Pre-Cambrian period which took place 600 million years ago, out of this period, mainly Eukaryotic organisms.( T. McDaniel)
 * Q: From which prehistoric period do the oldest fossils that come from organisms with bodies come from? Approximately how long ago was this and what types of organisms could be found during this period? (N. Braun)**