Saturday, April 9, 2011
From advantageous to not
In chapter 11, Shubin explains how we run into physical problems due to differences in the structures of our ancestors. Can you think of any genetic diseases or inefficiencies that we suffer from due to our incompatibility with fish? Furthermore, can you think of any characteristics that we currently have that could be a hindrance in the future?
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Diabetes, a disease in which "blood glucose, or sugar levels, are too high", is a disease that affects about 10% of the American population today (http://www.nlm.nih.gov/medlineplus/diabetes.html). There are two types of diabetes. Type 1 is when the human body is unable to produce insulin and type 2 is when the human body is unable to make or use the insulin well. Because of this, cells do not get the energy needed to perform cellular respiration because glucose stays in the blood rather than being broken down and used to create ATP through cellular respiration. Diabetes is most of the time genetic; however, it can also be caused by an unhealthy diet. Because fish do not have any other options to eat, such as Starbucks and McDonald’s, there is no big risk of their diet being a factor. Fish are capable of getting diabetes, because of the presence of a pancreas. However, it is rare in fish to have diabetes because they are more immune to the disease as they live a constant lifestyle. Humans also suffer from heart disease which can lead to a series of heart attacks and strokes. Humans contain a 4 chamber heart with a pulmonary circuit and a systemic circuit (Campbell 902). Fish on the other hand only have 1 atrium and one ventricle. This is an advantage over humans because the heart requires less energy to pump blood throughout the body. The ventricle pumps blood to the gills where gas exchange occurs. From there, the blood is sent throughout the body to different body capillaries to give oxygen rich blood to cells. With less work, less fatigue occurs. Thus, fish are less prone to heart disease because their hearts will never be overworked and will last as long as they live. Also, humans are a much larger figure. Thus, pumping blood throughout the whole body requires a lot of energy. All this energy is not used in fish as they have a smaller body that requires less work to pump blood to the rest of the body.
ReplyDeleteAlthough many similarities are not present, it is known through scientific research that fish is a healthy diet for humans. Fish gives humans the necessary Omega-3 molecules which help lower blood pressure and heart rate. Also, “eating fish reduces the risk of death from heart disease, the leading cause of death in both men and women” (http://jama.ama-assn.org/content/296/15/1926.full). Fish are seen to be healthy supplements to the human diet. Further research is needed to see if fish genes can help humans become immune to diseases such as diabetes and heart disease. However, as an alternative, fish is an excellent source of nutrition that can help lower the chances of getting heart disease, which is always a positive aspect.
Sources:
http://www.cichlid-forum.com/articles/biology_of_fish.php
http://www.ideacenter.org/contentmgr/showdetails.php/id/1113
Campbell
http://jama.ama-assn.org/content/296/15/1926.full
Shreeraj Patel
shreeraj.patel1@gmail.com
In addition to the diseases that Shreeraj mentioned, another disease that we suffer due to our incompatibility with fish is hemorrhoids. Hemorrhoids can be inherited genetically or one can get hemorrhoids many other ways. A main cause of hemorrhoids is obesity (WebMD). This is because excess weight can increase pressure on the pelvis and abdominal veins (WebMD). This pressure causes stress which contributes to hemorrhoids. As Shreeraj mentioned, we are susceptible to obesity because of our incompatibility with fish, and therefore, we are also more likely to develop hemorrhoids.
ReplyDeleteIn addition, we are also susceptible to many other genetic diseases such as Down's Syndrome, muscular dystrophy, and hemophilia because of incompatibility with fish (2). The interesting thing about these genetically inherited diseases are that they are caused by mutations of genes that are not essential (2). The genes that these mutations are caused by have no function for us, but they may have been important for fish. It is likely that through evolution, the need for those genes has been lost, but we still have them, since we evolved from fish. These non-essential genes can cause us problems when mutations occur.
Sources:
http://www.webmd.com/a-to-z-guides/hemorrhoids-cause
http://www.economist.com/node/12592274?story_id=12592274
Marissa Lobl marissa.lobl@gmail.com
Along with the diseases Shreeraj and Marissa talked about, hiccups are another inconvenience experienced in mammals because of incompatibilities with fish. Hiccups are an annoyance caused by sudden involuntary contractions of the diaphragm. As these contractions occur, “the opening between your vocal cords snaps shut to check the inflow of air and makes the hiccup sound” (http://www.emedicinehealth.com/hiccups/article_em.htm). The contractions of the muscles result in a sharp intake of air, and soon afterwards a flap of tissue in the glottis (at the back of our throat) closes the top of our airway. The center that controls these hiccups is a small patch of tissue in the brain stem (190). The brain stem can send nerve impulses to breathing muscles in our bodies. These nerves are seen in both fish and mammals. However, in fish, the nerves that control the breathing muscles do not have to travel very far because the gills and the throat are generally surrounding the area of the brain that controls this. This is unlike in mammals, where the nerves that control the breathing muscles leave from the neck, which is far away from the diaphragm and the other breathing control muscles. Because the neck is so far from the diaphragm, this can cause problems because “anything that interferes with one of [the] nerves can block their function or cause a spasm”, (190) which is how hiccups happen. So, the setup of the nerves that control breathing extending from the brain stem works well in fish, but causes problems in humans and other mammals.
ReplyDeleteSources:
Your Inner Fish
http://www.emedicinehealth.com/hiccups/page2_em.htm
Danielle Webb (dwebb456@gmail.com)
Along with diabetes, hemorrhoids, and hiccups, people are also susceptible to sleep apnea as a side effect to incompatibility toward the structure of the throat of the prehistoric fish to the structure of the throat of today's human being. Sleep apnea is especially prevalent in obese individuals because flaps of skin below the chin are more likely to push down upon the air passage in the throat. Sleep apnea is when "the muscles of our throat relax". (189) In this way, an individual is not able to breath for about 10 seconds and the individual is subject to sometimes hundreds of awakenings each night. Sleep apnea is seen in "about 2% of women and about 4% of men between the ages of 30 and 60." (Bassiri & Guilleminault, 2000). Sleep apnea is the direct result of the ability of humans to be able to talk. Because prehistoric fish did not need their air passage to produce sounds for communication, their throats were well-adapted to simply drinking the water around them. However, a human being is capable of conversation and therefore has a structure that the throat is not completely capable of supporting because evolution has yet to produce throat walls that are incapable of collapsing on themselves. On the other hand, sleep apnea is treatable through surgery or drug therapy and medical technologies surpass the need to evolve in order to obtain a more stable air passage that can withstand the relaxation of throat muscles during sleep.
ReplyDeleteSources:
Your Inner Fish
Psychology Themes & Variations Sixth Edition
Yekaterina Khavkhalyuk (kittykatx93x@yahoo.com)
Along with hiccups, hernias are also what humans are victimized with (mostly males) from from water to land transition. Hernias leave human suspectible due to the descension of the testes and the convolution of the spermatic cord throughout the pelvis. This has weakened our lower abdominal wall. http://www.dormivigilia.com/?p=1475
ReplyDeleteThe fish anatomy contains gonads that extend towards the chest area, approaching the heart unlike mammals. This arrangement is typical in most fish where the gonads lie towards the anterior part of the body. Fortunately for us mammals, our gonads are not located in that area or we wouldn't be able to sexually reproduce.
In the male human anatomy, sperm is secreted inside the scrotum in a sac that can expand/contract due to temperature changes (193). This allows for healthy sperm, and the external gonads are recognized as a sexual signal, which promotes reproduction among mates.
Our gonads have begun development similar to a shark's-near livers. As testes grow to develop, they descend. As we contract abdominal muscles, or guts are able to escape the body cavity and are squeezed next to the spermatic cord.
Unlike male, the female abdominal wall is stronger due to not having a tube running through it.