YIF: Chapter 8

This chapter titled "Making Scents" is, like the chapter suggests, about the nasal passage and smelling. Shubin spend time talking about the evolution of smelling and how this is relevant to the evolution of smelling to animals and even us humans. Shubin makes a remarkable statement that "our sense of smell allows us to discriminate among 5000 to 10,000 odors." It is very fascinating that out of all the molecules in the air we are able to pick out "up to one part per trillion." The connection to evolution is that "3% of our entire genome is Devoted to genes for detecting different odors." You can trace back to the genes for smelling out from the history of animals. This can be seen by looking at which genes are being expressed in fossils that are extinct or in animals that are still alive. What I found most interesting was how we smell. We smell by tiny molecules in the air which will actually attach themselves to neurons in our nasal passages. The complexity of these neurons is incredible. We have thousands of genes that express for the nerve cells that enable us to detect odors. And apparently we lost many of these genes throughout our evolution. According to Yoav Gilad "primates that develop color vision tend to have large numbers of knocked out smell genes." Going with the assumption in this book that we are we, as humans, are ancestors from primates, we can tell that we have lost large numbers of smell genes for our color vision. This chapter relates a lot to big idea one and four. For big idea one the process of evolution for smelling shows the diversity of life. As we saw in this chapter dolphins had blowholes and lampreys had a nostril and we, humans, have external and internal nostrils. As we look throughout our evolutionary history we see that the amount of genes for smelling has been increasing, this attributes to the diversity of life. For this chapter's connection to big idea for we see the molecular system of smelling and how our brain interacts with this. We see that small amounts of molecules enter through our nose and attach themselves to neurons and our Nasal passages. The book goes on about how the brain interprets these neurons and all of which is explained in great detail in this chapter. An essential question that can be made from this chapter would be, "How does an organism gain or lose the ability to smell?"