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Nilay Sharan AP Biology 18 August 2012
11
Based on Mr. Shubin’s accounts, fossil finding is not an easy task and the success rate of finding fossils are actually low. If one wants to find fossils, he/she would first need to find a good site, one that would be more likely to have fossils. According to Mr. Shubin there needs to be a “convergence of three things” which would maximize the chances of finding fossls. The rocks need to be of the right age, right type for preservation, and those exposed at the surface. The rocks and the fossils situated in the rocks can tell a story about the time and the animals there. Mr. Shubin provides an exmaple of the 365 million year old rock with the amphibian fossil and the 380 million year old rock with fish fossils; then based on that he says that the transitional fossil must be situated in a 370 million year old rock. Mr. Shubin later on decides to work in a more fossil suited place in Canada, near the Arctic Circle. There he had hoped to find the transitional creature from sea to land. After much search and failures, they came across a few breakthroughs. In 2004, Mr. Shubin’s team actually found what they were looking for—a flat headed fish. After further excavation the full creature was revealed. The new found creature had both fish and land-living animal features like scales of a fish and neck of an amphibian. The picture is the creature found by Mr. Shubins team. This creature is the centrepiece of Mr. Shubin’s first chapter, his goal, and how he was able to achieve this goal of finding this creature. The caption in the picture “When Fins became Limbs” is the question Mr. Shubin tries to answer, and all other scientists are trying to answer as well.
Most living organsims fossilize after death, so fossils in exemplary condition are easily found all over the world.
There are some crucial flaws with this statement, and it is not so much the first part as much as it is the second part where it says that fossils in, “exemplary condition are easily found all over the world.” If this statement was true, then humans would have the answer to evolution already and the controversy behind it would have also been ended. Also, Mr. Shubin’s expedition to the Canadian Arctic would not have been a big story—actually he wouldn’t have to go to the Arctic if the statement was true in the first place. The fact of the matter is that this statement is false simply because there are changes in the earth that disallow for fossils to remain in exemplary conditions or be found at all. One such example is the one Mr. Shubin discussed in the first chapter regarding the changing temperatures in the Arctic, which “crumbles the surface rocks and fossils” (1:20, Shubin). Also the seismic and volcanic activity would either destroy the fossils present, or it would cover the fossils with debris and rock which would make them inaccessible. Through both these scenarios, the statement provided is false.
Nilay Sharan AP Biology 18 August 2012
11
The hand may seem like a minor, yet important part of the body. The hand serves a major purpose of allowing accessibility and variety with movements. Therefore, the ability for humans to move and do as they please. The image shown is the inside of the hand, which shows the bone and muscle structure of the hand. Mr. Shubin opens the second chapter with this, where he had to dissect a human, and despite great success emotionally and academically with the abdomen, had a hard time with the hand due to an emotional connection he had made. The main point of this anecdote from Mr. Shubin was to plant the idea in the readers’ mind that if such a connection between two different people’s hands could be made, maybe there was a possibility there could be an connection, maybe evolutionary, between two different creatures in different taxonomical groups. That eases the reader into the main topic of the second paragraph—the hand/fin of the fish Mr. Shubin discovered, the Tiktaalik. He also discusses two men very crucial to evolutionary science—Sir Richard Owen and Charles Darwin. Owen said that there is a basic structure to all limbs regardless of taxonomical differences (within the Animal Kingdom of course). It was the one main bone, two sub supportive bone, “a bunch of bones”, and the fingers. Owen had no idea how this came to be, but he held strong with this theory. The next part of the image is also the metaphorical message of the second paragraph of looking under the surface, past the obvious. The image depicts what’s beneath our hand, just as what’s past the obvious differences between the Tiktaalik and humans. While the fish was an amphibian from a long time ago, it had a very similar bone structure in its fin, to those in the human hand. The most striking being the one of the wrist bone. Based on this, the environment of the fish, and the rest of the skeleton, Mr. Shubin came to the conclusion that the fish had the ability to do push-ups and needed this wrist function to walk on the bottom of the water body it lived in. Thus, an explanation is proposed as to what this structure was, why this fish needed this structure, and most importantly, what it means to the evolution of animals from sea to land. Lastly, this structure answered the question of why Mr. Shubin was so emotional when he had to dissect the hand of the cadaver. The hand does way more than lift an object, write a story, hold a sibling’s hand—it tells a story.
Humans and fish are nothing alike: we have hands with fingers, they have fins.
Yes, initially one would agree with this statement. It holds validity and truth. If you asked my nine year-old brother to dispute this statement, he couldn’t because that’s all he sees ( I think). The fish and human are different, our environment, needs, diet, social interaction, place in the food chain, and others. But once again, we have to turn to Mr. Shubin’s main metaphorical message in the second passage of discovering what’s underneath the surface. So initially, yes the fish and human may seem to be different, but when we look underneath the surface, past the skin, there are some striking similarities. The first one being bone structure as explained by Mr. Shubin. Mr. Shubin discussed the Owen bone structure—one bone, two bone, a bunch of bones,
and the fingers. This structure is present in the fish and the human. Furthermore, not only do the fish and human have a common limb structure, we may also have a common ancestry. It may be, MAY be possible that this fish discovered by Mr. Shubin could have been the ancestor of BOTH humans and fish. In which case, fish and humans are similar again. So when faced with the statement like “Humans and fish are nothing alike: we have hands with fingers, they have fins,” one might agree initially when not familiar with Mr. Shubin’s work, but when we look deeper, under the skin we hold this statement to be true conditionally.
Nilay Sharan AP Biology 19 August 2012
11
The Sonic Hedgehog Gene was the primary focus in the entire third chapter. The manipulation of this single gene has the ability to create major deformities in any embryo. There were two groups of people in this chapter who ran experiments directly related to the gene. The first one (chronologically) was the one run by Cliff Tabin in 1993, where his group tried to simply discover the gene that controlled ZPA, a patch of tissue that causes the pinky side of the hand to be different from the thumb side. Before the success of the experiment there was a general cloud of doubt surrounding what controlled ZPA. It was initially “some molecule”. The group noted a hedgehog gene in flies that made one body segment of the fly different from another. It eventually moved on the see this occur in a much larger animal, the chicken. There were conclusions made. The first, every limbed animal has the Sonic Hedgehog gene. Next, the gene is active in the ZPA tissue. Thus, if Sonic Hedgehog gene was turned on properly early on, it would impair the growth of the arm altogether, and the later the gene became impaired, the arm would develop accordingly. Sonic Hedgehog is one of “dozens of genes that act to sculpt our limbs from shoulder to fingertip by turning on and off at the right time.” (Shubin 3:53) With these questions answered, enter Randy Dahn, the second scientist in the chapter. Randy wanted to do the same thing Tabin did on chickens, on skates (cartilaginous fish related to the sting ray). Randy wanted to see the connection between skates, chicken, flies, and humans via the Sonic Hedgehog’s ability to cause major malformations. The first problem was solved fairly quickly and it was confirmed that there was a shark/skate Sonic Hedgehog gene. Next the questions arose “Where is the Sonic Hedgehog active?” and “What is it doing?” Randy studied this and noted that the time where the gene activates was the same in skate as it was in chickens, the location of activation—the back end of the fin (our pinky)—also the same. That led him to the Vitamin A experiment, where he would manipulate the Sonic Hedgehog gene by placing it on the directly opposite side. He injected this sample into the skate. The gene was behaving the way Randy had expected in the end, there was the desired result. A complete mirror image duplication in the skate fin was visible. Through Tabin’s experiment on chickens and flies and Dahn’s on skates, there were some major breakthroughs made. First, the existence of the gene pictured. As a result, the main theme. There was a gene in all animals. So, there was an inner fish in humans as well as an inner chicken and inner fly and inner skate. We are all connected despite our differences.
Each cell in a human body contains a unique set of DNA. This allows some cells to build muscle or skin and some cells to become arms versus fingers.
Once again, the disputable statement only holds some validity. The human body has specialized cells, leading to specialized tissues, and so on and so forth. But, the specialization is not due to the unique set of DNA because the DNA in each of our body parts is the same for every individual. But rather, it is the gene in our DNA like the Sonic Hedgehog one that controls the specialization in our cells. By turning on and off at set times, the gene is able to create “deformities” in certain cells. These deformities are what create the cells in our body become muscle cells or skin cells. This is also supported by Darwin’s theory, the famous “Survival of the
Fittest” or Natural Selection. In an example of a pack of 100 white moths, there is one darker moth that exists due to the fact the gene in his DNA that controlled pigmentation was flawed causing the entire moth to be dark. As time progresses and as this trait becomes more favorable, this trait is getting passed, and more and more moths are getting darker due to that one dark moth’s “deformity” that resulted due to a GENE that was flawed. Therefore, it is not a unique set of DNA, but genes activated at certain times that allow cells to build muscles whereas others are arms.
Nilay Sharan AP Biology 19 August 2012
11
The DNA with the light switch in front of it is more or a less a pictorial representation of the main focus in chapters three and four—the single gene that is activated in certain times to make definite parts of body. This focus was more prevalent in chapter three whilst discussing the Sonic Hedgehog gene and ZPA, but it also applies here. In chapter four, Mr. Shubin discusses his early endeavors again, this time when he first went with his college professor on a fossil expedition and how he obtained and eventually led his own expedition. In the second expedition, he introduced us to something called tritheledont, an early mammal living amongst reptiles—the earliest mammal which more or less resembled a mouse. The way the team was able to find out
that this creature was a mammal was by looking at the composition of the bone and then the teeth as well. The bone was made out of hydroxyapatite, the compound in other mammalian bones, but the main give away sign was the shape of the teeth. Teeth, like the hand discussed in chapter two, is a body part that is useful because of its abilities and the fact that it can tell a story. Teeth can tell us the diet of an animal and the other such habits. In Fox’s hit show Bones, the chemical compositions on the teeth is one way the investigators find out about their victim skeleton. Mr. Shubin ties this in with another key discovery (not his) the conodonts. The conodonts were discovered in the 1830’s but no one really knew what it was until much later when it was seen in the fossil of a much primitive lamprey (jawless fish). This was one of the earliest teeth discovered in paleontology which brings us to our next question, why did hard bones and teeth arise? The first hard body part was the tooth, not the bone (a common misconception apparently). Therefore, the hard bone arose not for protection but hunting. So as animals got big teeth, their prey needed big bones for protection and this “arms race” raged on. Once again we see this kind of mutation that can be explained through natural selection and the activation of genes in the DNA. The light switch on the DNA, if you will, to explain the arrival of hard body parts—the teeth and the bone. It is this kind of evolution in animals that has helped shaped our skeletal system and our teeth as well.
Teeth evolved through time, after bones, as they became a beneficial adaptation for protection against predation.
After reading chapter four, I can say with the utmost confidence that this statement is disputable. First off, the earliest recording of any hard body part—bone or tooth—was the conodonts in the primitive lampreys and those were teeth. That completely negates the first part of the statement that teeth evolved after bones. Unless there is new evidence to prove that bones existed before teeth, we have to believe (for the time being) that teeth came first. Next, the second part of the statements hold partial validity as well. “Adaption for protection against predation,” is another fallacy based on the same example of the lamprey. The lamprey is not a predator or prey, rather it is a parasite. Nonetheless, it uses its hard body part for its own gain. Similarly, we can turn to one of the ocean’s most primitive fish and its most feared predator, the shark. The shark’s inner supporting system is that made of cartilage, not bone, and its hard part is its tearing teeth. The shark and lamprey are two, primitive examples that bones came after teeth as an adaptation for protection. The teeth came as a beneficial adaptation for predators since the advent of teeth allowed predators to tear apart its prey. Bones came as a sort of body armor against the tearing teeth.
Nilay Sharan AP Biology 19 August 2012
11
According to Mr. Shubin, lawyers are like sharks and there are a few jokes regarding similarities between the two. I personally like that because the shark is my favorite animal (along with the white tiger) and I want to pursue a career in law (hopefully). This image draws that parallel between lawyers as sharks as we see shark fins emerging from the water as they evolve into lawyers. Once again, we see a deeper meaning, a subliminal message that Mr. Shubin wants us to see. First, there is a common evolutionary background between the shark and the human, so as the fins become the caps, we can make the connection of the evolution of humans as we were once (maybe) sea animals or maybe sharks. Actually, in this chapter we looked at the embryonic stages of both the human and the shark and there are some parallels that anyone can see with the naked eye. Actually, if we removed the labels, only an expert biologist would be able to correctly distinguish and label the two embryos. There are four arches during embryonic development each that helps make facial tissues, nerves, and bones in our head. These same arches are present in sharks as well and they make the same organs/nerves/tissues. The diagram on page 91 of the human and shark embryo shows the close correlation between the shark embryo and the human one. Once again, we see an inner fish. There is an inner ocean predator within us that takes shape during our embryonic development and later on changes. In the following page, there is a diagram of a fully developed shark and human and that allows to see clearly the development of a shark and the human. Despite our differences taxonomically, ecologically, and mentally, there is a striking similarity between the shark and the human. So when lawyers are like sharks, and we have a hidden shark, therefore we have a hidden lawyer in us I suppose. This also traces back to what was mentioned in chapters three and four regarding genes having the ability to control structural production during the development phase of the fetus. In chapter five we don’t discuss the Sonic Hedgehog gene as much as we dot the Otx and the Hox genes. I have heard of these before, but I had no idea what they did until now. Apparently Hox genes have the ability to map
out our gill arches that distinguishes our ear bones from our mandibles, so on and so forth. Therefore we see a recurring theme of a simgle gene with the ability to create “deformities” that help create different parts of our body—all as a result of the timing of the activation of a single gene and such. Not only are we like sharks, but also invertebrates. Mr. Shubin discusses in the end how humans and worms are able to keep their central nerve intact via a jelly like substance that protects it. The major difference is we have bone that protects our jelly like substance and the worms don’t. Another result of gene activation, I suppose.
Humans and sharks both have four gill arches as embryos, but the germ layers and arches develop into unrelated structures in each organism.
As I have done for the previous disputable statements, I will first proceed by breaking this one down and then stating my disagreements, and lastly justify my disputes. “Humans and sharks both have four gill arches as embryos.” The first part of the statement is true. Mr. Shubin spent a good two to three pages and a few diagrams to extensively explain that. So there isn’t much to dispute something that is empirically supported. But, “the germ layers and arches develop into unrelated structures in each organism.”This is where I firmly disagree because this is not true. Sharks and humans do look different, don’t let the swimming of Michael Phelps tell you any different. However, the gill arches during the embryonic stage do create similar structure in use, not appearance. The first gill arch creates the cranial nerve in both humans and sharks, the trigeminal nerve. The cells of the second gill arch gives us cartilage and muscle that helps the creation of the stapes, as well as another bone, the hyoid, that assists in swallowing. In a shark, the same arch helps with jaw production that compares to hyoid. In the third and fourth gill arch, for humans it produces structures necessary for speech and swallow and for sharks it includes parts of tissues that support the gills. So when faced with the statement, we see a misconception that has been rectified by empirical evidence provided by Mr. Shubin’s fifth chapter. That indeed, sharks and humans have gill arches in the embryonic stage, but unlike the statement proposes, they do in fact develop into RELATED structures in each organism.
Nilay Sharan AP Biology 19 August 2012
11
There is a recurring theme in the past few chapters regarding genetics in animals and the effect of genes in any animals. Also, there is a consistent reference to embryonic development and the striking similarities between two completely different species’ embryos. Instead of an image, we
go a recipe for cookies. After the ingredients and the basic recipe of making the cookies, we received variations. We would have to make minor changes in either ingredients or the cooking process in order to actually make the variations we desire. Here we see a parallel between genetics and the recipes provided. Mr. Shubin has given us a few lessons regarding genetics and has introduced us to Sonic Hedgehog, Hox, Otx, Noggin, and other similar kinds of genes. The underlying message regarding these genes is that minor changes in location and timing during embryo development lead to major changes in the subject. These mutations are what cause natural selection. In this chapter specifically we focused on the Hox gene. The first comparison regarding the Hox gene was the one between flies and humans. Flies have one set of these genes while human have four. The first reason that we have more is because we are much larger and therefore much more complex creatures. Regardless of our size and complexity, the head to tail organization of the body is under the control of Hox genes. In both flies and people, the gene activity corresponds to its position on the DNA. The new concept introduced in this chapter to use was the one regarding the tiny patch of tissue which contained all the information to direct other cells to create a full body plan—an architect, if you will—of the development of a creature. This was the Organizer tissue. The Organizer was found by two German scientists, and the scientists discovered that even if we took the Organizer tissue from one embryo of a species and put it on another embryo of another species, the end result would be an exact duplicate of the second embryo species. It had basically created twins. Going back to Hox genes, the organization of the gene is not only true for flies, humans, fish, reptiles, but also sea anemones and invertebrates. In regards to the recipe we have Mr. Shubin says something very similar. On page 115 he says, “Like a cake recipe passed down from generation to generation—with enhancements to the cake in each—the recipe that builds our bodies has been passed down and modified for eons.” At the end what we can see that basic correlation that certain even the most minor modifications can actually make the biggest difference. Although we are primates and mammals, we still have that inner fish.
Scientists work in isolation: it is counter-productive to repeat another scientist’s experiments or to consider research that is not directly related to the organism that you are studying.
First of all, scientists do not work in isolation. Throughout all the examples provided by Mr. Shubin and in all scientific education, it is evident that a scientist cannot simply work alone and achieve a scientific breakthrough. While it may seem like that because only one scientist gets the Nobel Prize, this is not true. In the event of the Organizer’s discovery it was not only Mangold but also Spemann who helped come up with that idea. Furthermore, it is not counter-productive to repeat another scientist’s experiments or to consider their research because most of the time it is the research and experiments of earlier times that give us insight and the background information necessary to actually come out with new information. Another example is Tyco Brahe and Johannes Keppler. Brahe was the student who expanded on his teacher, Keppler’s, work and that allowed both Keppler and Brahe to be immortalized in astronomical science.
Similarly the works of Richard Feynman, Albert Einstein, and Robert Oppenheimer would never have been achieved if there were no basic foundation for physics set by people like Newton. In the biological field, Watson and Crick needed the earlier results of a woman (whose name eludes me right now) in order to discover the double helix shape of DNA. At the end of the day working in isolation is never good because it puts too much pressure and significantly hurts efficiency of scientific work. Hence, why no scientist works alone. Also, trying the experiments of others and using their research is not counter-productive because their successes and failures can help us see into the truth and the future. It gives us the necessary background information and insight to our own discoveries.
Nilay Sharan AP Biology 20 August 2012
11
Everything around us made of bigger stuff. Those bigger stuff make up even bigger stuff. Take, for example, a word. A few words make up sentences, a few sentences make up a paragraph. Paragraphs make chapters, which make books. There is a similar thing that occurs in biology and the image provided is another pictorial representation of that idea. In the image there are a bunch of what seem to be rope. In that bundle, there are individual ropes, which are made up of strands as well. Each of these smaller components come together to make the big picture. For the image it’s the bundle of rope, in the book it’s the organism. Mr. Shubin explained this basic concept to us through the examples of humans, a Pre-Cambrian creature, and the sea sponge. Since a very early age, we have been told that everything is made of cells. That they are “the building blocks of life,” but then what makes our cells different from that of a plankton, and how come we have different body parts? Cell specialization is what enables us to have muscle cells, bone cells, brain cells, and such. It is the job of the genes to create these specialized cells. A single cell can’t do the job of a muscle or even a strand of muscle. It takes a few cells to come together into what is a tissue. Tissues are key components of an organ because the tissue contains the specific kinds of cells that are needed for the organ. Brain tissue would be different from skin tissue because they both contain different kinds of cells that are needed for multiple different reasons. When tissues are amassed together, they form organs—key parts of our body that do a single task and keep us alive. The first ones that come to mind are the brain and heart. Understandably, the heart pumps the blood in our body and the brain is our central processing unit. But then again ask yourself this: are the both solo acts? Do they do their jobs alone? When I need to pick up my pencil, my brain wants me to pick up the pencil. But I can only do so if that message is relayed via my spinal cord and nerves. There I mentioned two other organs. Hence, when organs work together, you have an organ system—each with its own function like breathing, thinking, excreting, etc. These multiple organ systems come together to make the organism. It’s astonishing really to see something so small be a key part of something so humungous big (relative to its size). That’s what the image tells us and that is what Mr. Shubin is telling us.
All tissues in the human body are made of similar cells that connect to each other in similar fashion.
As of before chapter seven, I used to believe the same thing that everything was this systematic. But I have been enlightened and can disagree with this statement. This statement is not wrong, but it makes a general statement that can be disproven due to the fact it’s not specific enough, or rather there are exceptions. First of all, tissues in the human body have cells similar in relation to cells within that same tissue. For example, cells in brain tissue will be similar to other cells in the same brain tissue, not to cells in a heart tissue. The next portion of the statement deals with connection and connectivity. Not all cells connect the same way and it’s not like condominiums or apartments where there is a common cell membranes. Rather that while there are certain kinds
of cells like muscle cells that might do that other cells like bone cells don’t. Bones stick by means of rivets. Some bind cells like cement does with the soles of shoes. (Example courtesy of the book) This rivet sticks to cell membrane of one cell and another cell and acts like a glue. Thus, forming a bond that holds these bones together nicely and tough. Furthermore, these rivets only bond to the same kind of rivet. Hence, not all similar cells connect to each other in a similar fashion. Furthermore, not all tissues in the human body are made of similar cells.
Nilay Sharan AP Biology 20 August 2012
11
This image is the baggage in our noses. In the final pages of chapter 8, Mr. Shubin says that humans have had a trade-off that has been taking place for a while now. The trade-off of smell for sight. It makes sense, humans have always been one to go based on sight such as first impressions, judging “books” by their “covers”, and even love at first, you guessed it, sight. Actually it turns out that the more we use our sight as a primary sense, the more we sacrifice our sense of smell. We will have and still retain the genes that control our sense of smell, these olfactory genes, but they will be rendered useless because we have rendered them useless. This is the reason why a blind man has a more keen sense of hearing and smell, because he hasn’t relied on sight as heavily as I have. As his life has progressed, more and more of his olfactory genes have been active; hence a better nose. Another common saying is, “you can tell a lot about a woman from looking through the contents of her purse.” Baggage is like a purse and the contents inside can give us insight into the person, or in this case, human beings. This baggage like the hand in chapter two and teeth in chapter four can tell a story about where we as humans come from and where and who is our inner fish. Fish have a very good sense of smell, and they need to. Predators like the sharks rely on it to find food, and it’s prey like the creature Mr. Shubin found needed it to stay away from sharks. In murky waters or water in general it is hard to see, so these fish relied on smell to stay alive. Their olfactory genes, which is present in all animals, were more active than ours today because they needed it. As fish evolved and as they moved onto land, vision became clearer. The need for smelling stuff has decreased because the ability to see has improved. The more and more these fish evolved into amphibians then reptiles, then birds, and now mammals, these olfactory genes are still present as a memory or a remnant of our fishy ancestry. Yet, they are not useful anymore and don’t function. Another biologist (whose name eludes me at this very second) had this theory that body parts came and gone based on usage. The more a body part is used, it is more likely to remain; the less it was used, it was more likely that it was going to be gone. This could be considered a variation of natural selection, but in a nutshell, the scenario I just explained could be the very reason we have functionless olfactory genes.
There are few genes dedicated to olfactory sense and they are similar in all organisms capable of detecting smell.
First of all, 3 percent of the human genome is dedicated to olfactory senses, needed to detect different odors. (As noted in Mr. Shubin’s book on page 144 chapter 8) So in a pool of 1000 genes, thirty of them are dedicated to smell alone. It may seem small initially, but when compared to the amount of jobs the human body does and all the genes needed for things like skin pigment, hair color, eye color, brain formation, limb creation—thirty seems like a humungous big number. This goes to show exactly how important the sense of smell was to our evolutionary ancestors whoever they may be. Moving onto my next area of analysis the
“similar[ity] in all organisms capable of detecting smell.” The only thing true and connected regarding olfactory genes and animals is that they are present in the same number in all organisms capable of detecting smell. That’s it. Other than that things are very different. If this statement were true, dogs and humans would have the same keen or unkeen sense of smell as each other as well as that of snakes and eagles. The only thing similar is the number, other than that everything else is different. For example, although humans and dogs both have 3 percent of genome dedicated to the smelling of odors, the dog will have more of their 3 percent actually functioning compared to humans.
Nilay Sharan AP Biology 21 August 2012
11
Like the hand and the tooth which were discussed in chapter 2 and 4 respectively, the eye also plays a very important role as an organ and as a evolutionary tool. To clarify, the eye is useful in the way that it helps us see objects and thus help us get around, but it also serves as a way to help us understand where we come from and also where and how our ancestors lived. First Mr. Shubin goes through the process of the eye—how it works and what are the basic structures working and what they do. He then explains a potential reason as to why we have three receptor making genes whereas other mammals (non-primates) have two; hence, why our vision is better and we can see with more and crisper colour. He attributes this genetic change to changes in the vegetation of the earth from a million years ago. Mr. Shubin says that monkeys in trees would benefit using colour vision because it would help them distinguish fruits and leaves so as to not pick the wrong fruits and leaves and in the end, survive. We then go into the 2001 study of Detlev Arendt who dissected a primitive worm, Polychaetes, to find that they had two ways of seeing. One was the standard eye made of neurons and opsins like any other invertebrate. The other one was a photoreceptor with vertebrate opsins and cellular structure, except this one was just primitive. So in a nutshell, Mr. Arendt had found a living bridge between two different groups of animals; maybe he found a piece of the never ending evolutionary puzzle of animals. Towards the end of the chapter, we turn to genetics and genetic studies, starting with that of Midred Hoge who had found a whole group of flies who were mutated to have no eyes at all. She called then eyeless. This mutation was then later found in mice and even humans (condition
called aniridia). So once again, there was this striking parallel between mice, flies, and humans. In the 1990’s, it was discovered that the fly, mice, and human genes responsible for eyelessness had similar DNA structures and sequences. They were the same. Hence, a normal version of the gene would trigger the formation of eyes. Of course, geneticists decided to mess with this gene. Walter Gehring then placed this eyeless gene anywhere he wanted on the fly: antenna, abdomen, wing. He found that everywhere he had activated the gene, a new eye would be made there. He took the mouse equivalent of eyeless and put in a fly. It made a fly eye where he had placed it. Thus, the conclusion arose that eyeless or Pax 6 (for mice) controlled development in everything that has eyes. The image provided is the cover of a book called Metamorphosis, I can’t necessarily see the cover due to my poor resolution, but the title metamorphosis is very significant because the metamorphosis in animals has led to a greater improvement in the eye. From a time where the early humans had poor, coloured vision to now, there has been a massive change that has allowed us to see better.
All organisms with vision have similar eyes and similar vision genes.
Whereas in chapter 9 where we learned that there are striking similarities in the eyes of flies, mice, and humans, as well the genetics of it, this statement is clearly untrue. First of all, not all organisms with vision have similar eyes. When looking at the diagram in Mr. Shubin’s book on page 151, there he makes a clear distinction in the eyes of humans, scallops, nautili, and limpet. There is a clear distinction provided in the graphics of the structure of their eyes, hence their vision. Even when we look at the closely related fly, their eyes are not similar to that of humans. According to the Biology book by Campbell and Reece (6th Edition; not AP), flies have a honey-comb structure that makes their vision appear like kaleidoscope. This however is not true in humans. We have one vision and our eye structure is more like that of a camera, not a kaleidoscope. Furthermore, the question of genetics is asked and the answer is simple. No. Non-primate mammals with vision have two receptor genes, whereas we have three. Most mammals to my knowledge have vision, but the genes however are not similar. In the end and at the core of this statement lies a general fallacy of generalization and vagueness that has been toppled both logically and empirically.
Nilay Sharan AP Biology 19 August 2012
11
The image I see is of a snowglobe. This snowglobe has an elephant in it. It has a tree. Against that tree, there is a human. Through this image, I can make basic connections between the image and the chapter, the book actually. First is the underlying message of the book. Everything is connected—the elephant, human, and the tree. All three are living organisms. The human nd elephant are mammals. Part of the same kingdom, and the same mammal classification. In regards to the chapter, both the elephant and the human use ears. The ears are used for listening. The ears are used for balance. The ears are also used for warming and cooling of the body. Finally, the snowglobe. The whole snowglobe is a major references in the chapter. The snowglobe is a reference to our ear and more specifically our inner ear. Like the snowglobe, the inner ear is fulled with tubes and gel. The snowglobe and the inner ear can both tell us if there is a tilt present. Like the “snow” particle in the snowglobe, the ear has these little tiny rocks (sort of) that rest on fluid filled sacs in our ear. Every time the snowglobe is tilted, the snow particle shifts towards the tilt. Just like that the rock particles tilt in our ear and the bend the nerve ending in the ear. Those then tell our brain that our head is tilted. Every time our head is bent, the rocks flop around and manipulate the nerve endings with which our brain can find out about the positioning of our head. Mr. Shubin talks about the effects of zero-gravity and acceleration on this system that our ear has of letting our head know about its position. The rock particles float around; therefore our nerve sense get all confused. Even when we move from start to stop on a car. When we jolt, so do the rocks and gel in our brains. Like everything in the human body, the
inner ear is connected to the brain, the nervous system, and even our eyes. The movement of the eye is controlled by eight individual muscles. These eye muscles have the power to keep our eye fixed in one certain point like a word, even when our head is tilted one way. Mr. Shubin then discusses the effects of alcohol to the ear. As we drink more alcohol, it gets diffused into the fluid in the inner ear. As more alcohol is in the ear, the gel swirls around more, stimulating the hair cells, and giving the brain the wrong message. When our brain thinks it is moving, it passes this information onto our eyes, and they start twitching. In the end, we learned about the evolutionary history and the genetics behind ears. Like Pax 6 discussed earlier, there is also a Pax 2. These genes are, once again, key to the development of the ear. However, these genes came to our evolution much later. These genes are tracked to a combined primitive version of Pax 2 and Pax 6 that is present in jellyfish. Also, birth defects to the ear also occur to the eye and vice versa. This is another connection to other primitive creatures. A connection. To our inner fish.
In humans, eyes and eaers function independently of one another; sensation in one does not affect sensation in the other.
To be honest, every time I read one of these statements, I feel like I’m having a conversation with someone. I give them this entire summary of the chapter, they give me this statement, and it’s as if they weren’t listening to me. In the closing words of my summary I said that birth defects to the ear often effects the eye, and vice versa. This is because the use of the ear is way more than just listening. The ear gives us a sense of balance and direction via the rocks, gel, and nerves in the inner ear. To reiterate what I said earlier. Every time our head tilts or moves, the rocks sitting on the gel in our inner ear moves as well. This stimulated the nerve hairs in our inner ear. The nerves report this shift to the brain and our brain tells the eight muscles in our eye to direct our eye as well. It’s a chain reaction. If this statement proposed were true, and the eye and ear were independent to each other, our eyes would be looking dead ahead even though our head might be rotated a full ninety degrees. This would happen because the head would tilt but here’s the thing. There is a little thing called the brain that makes the connection between the brain and the eye. Hence, every time our head moves, the eye also moves (there are exceptions) Without this major connection, we would be like that one pirate from Pirates of the Caribbean who had the wooden eye. Also, every time our head tilts fast, our eyes aren’t able to clearly catch what is in front of us because the fast tilting does not give the brain enough time to send the signal to our eyes for every position of our head. In the end, the eye, the ear, and the brain are all connected. Thank goodness they are.
Nilay Sharan AP Biology 21 August 2012
11
The image provided to us for the final chapter of Mr. Shubin’s book is what we would, in modern times, call a couch potato. It is literally a potato in a couch sitting and watching the TV—quite the behavior of a couch potato. Mr. Shubin in the previous ten chapters went through great lengths to explain the connection between humans and different animals, primarily fish, sharks, flies, and worms. We saw how the hands, genes, eyes, ears, nose all evolved from the early creature to what it is now. Mr. Shubin has wrapped everything up, but under all this he gives us an asterisk, a clause. The image is more that just a representation of one of the things discussed in the final chapter. It’s a warning. A warning telling us to not be couch potatoes, not be lazy and lead a sedentary lifestyle. According to Mr. Shubin, a lot of the injuries and other medical things that happen to humans are a result of a “trade-off” during evolution. During our evolution into Homo sapiens sapiens, we received a lot of key and distinct abilities, but we also inherited a lot of problem. We are a little bit too fined tuned for our inner fish. For example, the human race isn’t designed to take a lot of weight in our legs and bodies unlike ants, therefore we have inherited knee problems despite the ability to walk on our “hind” feet. Hiccups are another example of an “incomplete” evolution. Hiccups are caused by the contraction of the glottis, an organ in the human and tadpole. The tadpole uses this to regulate breathing through its gills or lungs. This is in the human for some reason, when it contracts and makes contact with our windpipe it makes a hic sound. Humans have the glottis, as does the tadpole, but unlike the tadpole, humans are incapable of controlling this flap. The most relevant example to the image is
the one that says that humans weren’t mean to sit around on their behinds all day and live a sedentary lifestyle. This can explain the obesity, heart conditions, and cholesterol issues in humans today. Humans were meant to be an active species of animals. Our inner fish did not allow us to be sedentary, and so we shouldn’t be.
Maladies of the human body are not related to our evolutionary past.
Actually, the truth is quite to the contrary. Maladies of the human body are a direct result of our evolutionary past. Mr. Shubin made the analogy of human evolution to that of the Volkswagen Beetle. He said that the humans are basically a beefed-up Beetle. For simplicity’s sake I will return to that analogy. When we take a car like the Prius, we see that the Toyota Prius is not by any means good looking as say the Ferrari 360 Modena. But, the Prius is more fuel efficient than the Modena. Say we modified the Modena to be more like the Prius—a more environmentally and fiscally better car for the average American. First, one might change the engine. A sedan does not need a V12 engine with almost 420 Horsepower. That saves the driver a lot of gas money and maybe service maintenance money. Next thing, the tires. Let’s change the tires of the Modena to be more like Prius. This move saves more money as well. At the end, when you edit the Modena, you don’t have the Modena. You have the ugly yet very efficient Prius. All the improvements made had a side-effect of making the car uglier. The maladies in the human body are just like that. The examples brought up in the book include the hiccup. The glottis, the organ causing hiccups in humans, is an evolutionary remnant from when mammals were formerly amphibians. Now instead of being useful, the glottis has become a constant pain in the human’s life. The same can be said about the tailbone. The tailbone has caused some serious problems. A few years ago I received a hit to the tailbone and that kept me our of the school team for a while. The tailbone serves no purpose whatsoever, yet we have it. The maladies don’t just apply to the useless parts of our body, but even those useful. But in the end, everything in our body is a result of our evolutionary past. To say that it isn’t is wrong.
