chapter seven

This chapter made me realize and appreciate how cool cells really are since they are able to build bodies without any blueprints or directions. Then Shubin mentions that "our component parts work together to make a greater whole" (118). This reminded me of how there are different organs in the body, dividing the work load, but they all work together to make up the different systems, such as the digestive system, the nervous system, and all the others - only in this chapter, it is on the microscopic level.

It made sense when Shubin explained "If there were no way to attach cells to one another, or if there were no materials between cells, there would be no bodies on the earth - just batches of cells" (124) since bodies are made up of cells that communicate with each other through the "glue/stuff" or molecules that hold them together so that they know how to behave, or else we'd be dead.

Also in the analogy of the bridge I learned that the molecular properties of the building materials are just as important as the shape, size, and physics of the structure since the materials have to be able to fit the design in the first place for the physics to work. In connection with this, the section on the different kinds of molecules such as the proteoglycan complex, collagen, and hydroxyapatite was very informative and it really helped in understanding the skeletal structure of the body, its pliancy in cartilage and its resistance in bones.

I found it interesting how Shubin compared humans to placozoans and sponges. I knew that sponges are capable of forming new bodies when separated. But then he says, "A sponge seems a far cry from a body, yet it has many of the most important properties of bodies: its cells have a division of labor; the cells can communicate with one another; and the array of cells functions as a single individual" (131) and it reminded me that humans really aren't much different from other creatures, knowing that our bodies came from unicellular organisms and so keeping in mind Shubin's concept that all creatures are just variations on one theme.

Throughout most of the chapter I didn't understand the difference between a unicellular organism and one with a so-called body, until Shubin explained the work of Nicole King on choanoflagellates. The difference is genetic and that choanoflagellates' DNA is similar to that of microbes instead of the DNA of sponges, therefore declaring that choanoflagellates are single-celled microbes.

Shubin asked the question, "Why the rush for bodies after such a very long time with no bodies at all?" (135). He then answered it with "Bodies may have arisen as a kind 0f defense... when predators develop new ways of eating, prey develop new ways of avoiding that fate... getting big is often a very good way to avoid being eaten" (136). This made good sense and reminded me of Darwin's "survival of the fittest" and that creatures/animals need to adapt to the surroundings in order to survive. I was amazed in Shubin's description of Martin Boraas and his work with the single-celled alga that responded to a predator by becoming a clump of hundreds of cells. I was also surprised that bodies appeared when the levels of oxygen on earth increased because I didn't know oxygen had to do with the body composition. (I thought carbon was the important one because of its ability to bond so well and makes up complex molecules? idk...) But then again the increase of oxygen makes sense in making bodies because Shubin explains "There was a reason to build bodies, and the tools [oxygen] to do so were already there... oxygen on the earth supported bodies" (138). I learned a lot from this chapter and now finding out so many things about life I agree with Shubin that "Life would never be the same" (138).

Alexis Jacalne