User:Martin.2489/sandbox

Evolution sandbox

Kelsie Martin Evolution Wiki bibliography 9/13/14 Tuesday 1020

Topic: The evolution of the appendix. Not only in humans but in other animals and why it developed the way it did in certain organisms.

1. “Vermiform Appendix.” Wikipedia.com. 10 Sept. 2014. Wikimedia Foundation, Inc. Web. 10 Sept. 2014.

The first article I chose is the wikipedia page for the vermiform appendix. This article gives basic facts about the appendix such as how it got the name Vermiform appendix and the anatomy of it in the human body. I found this article very helpful because it goes in good detail about the evolution of the appendix. The article discusses how certain animals no longer have an appendix while other animals appendix is very well developed. This article also gives insight on what the possible functions of the appendix may be and how that could vary among different animals. This article is a good starting point for my project and it will definitely help me overall.

2. Barras, Colin. “Appendix evolved more than 30 times.” news.sciencemag.org. 12 Feb. 2013. American Association for the Advancement of Science. 12 Feb. 2013. Web. 10 Sept. 2014.

The next article I chose is questioning the function of the appendix and more specifically the evolution of the appendix. The article mentions that Darwin was one of the first people to hypothesize that the appendix evolved when human ancestors switched from a plant diet to a more fruit diet. The article then goes into telling about multiple studies that show how the appendix has changed over the years. One study claims that the appendix has possibly independently evolved 32 times and perhaps 38 times. The article then goes on to tell about the new theory of the function of the appendix. Scientists think that perhaps the appendix is a safe house for good digestive bacteria. The scientists theorize that when the immune system is trying to fight off bad bacteria that the good microbes can hideout in the appendix until the bad bacteria is gone. One scientists makes a good point in saying that if the appendix has such a helpful function for good bacteria, well then why doesn't every animals have one. I find this article very interesting and gives very good insight on the origin and evolution of the appendix.

3. MBD. “Scientists finally discover the function of the human appendix.” politicalblindspot.com. 22 July, 2013. 2014 Political Blind Spot. 22 July, 2013. Web. 10 Sept. 2014.

The third article is more about the recent discovery of the function of the appendix. As in the other article the theory is that the appendix is a safe house for good bacteria. From the evolutionary stand point the article claims that it seems that the more omnivorous an animal becomes, the smaller the appendix gets. The koala has a very large appendix thought to aide in digestion of the heavy leaf diet. It is predicted that if the koalas eucalyptus trees were to die out and the koalas had to switch diets, that they too would get a smaller and smaller appendix. So perhaps the appendix does more than just harbor good bacteria during a time of infection. I like this article because it gives a specific example of an animal with a distinct appendix and why scientists believe its appendix is so large. It makes it a bit easier to understand why humans appendix's may have shrunk so much.

4. Duke University Medical Center. "Evolution Of The Human Appendix: A Biological 'Remnant' No More." ScienceDaily.com. ScienceDaily. 21 August 2009. Web. 13 Sept. 2014.

Article four is mainly challenging the ideas of Darwin about the appendix. Darwin thought that the appendix was just a shrunken up skin fold of the cecum. He thought that once human ancestors switched diets from plants to more fruits that the cecum shrunk and created the appendix. This article goes completely against this idea. In this article scientists say that Darwin couldn't of been right for two reasons. One reason was that some living species have an appendix attached to a large colon. The second reason was that the appendix is a very wide spread organ in nature. The article also mentions that scientists believe the appendix has been around for much longer than Darwin thought. Perhaps as long ago as 80 million years. The article claims that Darwin just didn't have as much technology and information as we do now. I find this article very informative because it not only tells about the evolution of the appendix but also about the different theories and how they have evolved to the idea that the appendix is no longer vestigial.

5. Warner, Jennifer. “Appendix may actually have a purpose.” webmd.com. WebMD, LLC. 12 Oct. 2007. Web. 13 Sept. 2014.

My last article is talking about how society today may be affecting the function of the appendix. This article again mentions the idea that the appendix harbors good bacteria while infection may be occurring but the article also says that society today may be leading to the vestigial traits of the appendix. The article says that because society is so sanitary and has good hygiene that the body might end up attacking the good bacteria in the appendix from an overreaction. The article also says that the hygiene now a days may lead to an inflamed appendix and possibly appendicitis. I chose this article because it talks about how society today may affect the evolution on the appendix in future generations. Perhaps the appendix will get even smaller because society already has so many good drugs and bacteria to put into the body. It's interesting to think that humans might be helping but at the same time are causing the appendix to disappear.

October 1st

Added Sentence The added sentence is in italics. The human's appendix averages 11 cm in length but can range from 2 to 20 cm. The diameter of the appendix is usually between 7 and 8 mm. The longest appendix ever removed measured 26 cm from a patient in Zagreb, Croatia.[1] ''The opening of the appendix is occasionally guarded by the valve of Gerlach, named after German anatomist Joseph von Gerlach. This valve consists of a semicircular fold of mucous membrane.'' [2]The appendix is usually located in the right lower quadrant of the abdomen, near the right hip bone. Its position within the abdomen corresponds to a point on the surface known as McBurney's point (see below). https://en.wikipedia.org/wiki/Vermiform_appendix

Talk 1 https://en.wikipedia.org/wiki/Talk:Vermiform_appendix I added a pretty important point about the location of the appendix and how it can tie into appendicitis. My point is number 26 on the content block and titled "Appendicitis addition" What I wrote is in italics. ''I read that the location of the appendix is very important in the diagnosis of appendicitis. Although the appendix is usually in the lower right quadrant, if it is located somewhere else, then the diagnosis may mimic other diseases. I find this important so that people will possibly look into appendicitis even if they have pain in other egions of the abdomen. I am not sure where to put this information exactly so I added it here first. Here is what I read and the citation for the page.

Identification of the normal position of appendix is important because in appendicitis variable positions may produce symptoms and signs related to their position, and hence can mimic other diseases (Sabiston et al, 2001; Bakheti and Warille, 1999).

I found this in this article. [1]

Martin.2489 (talk) 12:38, 1 October 2014 (UTC)

Jump up ^ Golalipour, M.J.; Arya, B.; Jahanshahi, M. (2003). "Anatomical Variations Of Vermiform Appendix In South-East Caspian Sea (Gorgan-IRAN)". J. Anat. Soc. India. Retrieved 1 October 2014.''

Talk 2 https://en.wikipedia.org/wiki/Talk:Vermiform_appendix#Surgery_section I added a suggestion to expand a bit more on two small portions of the appendix page. I found separate pages that could help define these portions a bit more. It is number 27 on the content section titled "Surgery Section" What I wrote is in italics. ''For the surgery section where it talks about removing the appendix to make a pathway for fecal movement or for urinary help, I believe there could be a bit more about the topics. Perhaps list the name of the fecal movement procedure (Malone antegrade continence enema) and perhaps mention the fact that the two procedures usually tie in with each other when patients have certain diseases such as Spina bifida. Just a suggestion that I think would be a helpful tidbit of information. Also add links to both Malone antegrade continence enema and spina bifida. [2]

Martin.2489 (talk) 19:40, 1 October 2014 (UTC)''

Talk 3 https://en.wikipedia.org/wiki/Talk:Vermiform_appendix#addition_to_the_function_section I suggested that there be a subcategory to the function of the appendix for just the fetus and young adult age range. I feel this may be vastly different from the function in adults, so I feel it might be important to add to the page. My talk is number 28 in the content section titled "addition to the function section." What I wrote is in italics. ''I read that the appendix plays a major role in the fetus and young adults. The article said that "Endocrine cells appear in the appendix of the human fetus at around the 11th week of development. These endocrine cells of the fetal appendix have been shown to produce various biogenic amines and peptide hormones, compounds that assist with various biological control (homeostatic) mechanisms." I feel like this could possibly be a separate subcategory of the function for the appendix. I don't want to add anything in case there have been other articles to contradict this idea. [3]

Martin.2489 (talk) 20:04, 1 October 2014 (UTC)''

EDITS TO PAGES I edited three different pages.

Added to the page Clostridium difficile colitis Recent research has been studying whether the appendix has any importance to the bacterial infection, C. Difficile. The appendix is currently a vestigial organ but is thought to have a possible function of housing good gut flora. In a study conducted in 2011, it was shown that when the C. Difficile bacteria were introduced into the gut, the appendix housed cells that increased the antibody response of the body. The B cells of the appendix migrate, mature and increase the production of toxin A-specific IgA and IgG to be released, for protection, into the blood. This leads to an increased probability of good gut flora surviving against the C. Difficile bacteria. More research needs to be done, but this discovery could soon lead to less severe cases of C. Difficile.

Added to Lymphatic system One other area that contains a lot of lymphoid tissue is the appendix. The appendix is thought to be made up of almost all lymphoid tissue. A scientist named Joseph Ransohoff simply stated that “the entire mucous membrane of the appendix is nothing but a lymph gland spread out.” The appendix has been compared to the tonsils in the amount of lymph tissue present. In the early 1900s the appendix was found to contain a lot of gut-associated lymphoid tissue (GALT) and after the discovery of this tissue, it was proposed that the appendix had an immune function. Whether the appendix is an immune organ is still debatable but regardless, the appendix consists of lymphoid tissue.

Added to Biofilm Recent studies in 2003 discovered that the immune system supports bio-film development in the large intestine. This was supported mainly with the fact that the two most abundantly produced molecules by the immune system also support bio-film production and are associated with the bio-films developed in the gut. This is especially important because the appendix holds a mass amount of these bacterial bio-films. This discovery helps to distinguish the possible function of the appendix and the idea that the appendix can help reinoculate the gut with good gut flora.

FINAL PAPER

The vermiform (“worm-like”) appendix is a 5-10 cm long extension from the cecum that develops embryonically. It is located near the junction of the small and large intestine. All hominids (humans and apes) have an appendix along with a few other mammals such as the rabbit and the wombat. The appendix is currently considered a vestigial organ, an organ that has lost all or most of its function through the course of evolution. (Smith 2013). Whether the appendix is still a vestigial organ has been under debate in the recent years. The appendix can cause multiple problems for the host with the most prevalent problem being appendicitis. This is when the appendix becomes inflamed and if not treated could rupture and possibly kill the patient. The appendix is predicted to be at least 80 million years old giving it plenty of time to evolve. (Duke Univ. 2009). The appendix has been estimated to have evolved independently a total of 32 times leading to the question of what was the appendix originally for and why did it change over time. (Smith 2013).

The appendix was first observed in 1521 by Berengario da Carpi and has since been studied by many other scientists. (Barlow 2013). The most notable scientist would probably be Charles Darwin. Darwin discusses the appendix in 1871 in his book On the Descent of Man. Darwin observed that the appendix is in humans and apes and while located along the digestive tract, it is too small to have any digestive functions. Darwin hypothesized that the shift in diet changed the function of the cecum and therefore the appendix. He stated that the diet was shifting from leaves to a more fruit based diet and therefore required less fermentation and so the cecum shrank. He thought the appendix was just a fold off of the cecum and so shrank with the cecum. For many years the appendix was considered a synapomorphy, a shared trait of two or more taxa present in the most recent common ancestor, of Hominoids because the appendix was not observed in many other nonhuman taxa. The world now knows this is not the case. (Smith 2013).

As stated in the first paragraph the appendix is believed to have evolved as many as thirty two times amongst mammals. It is believed as well to have been lost less than seven times suggesting that it has a high fitness or is closely related to another characteristic that has a high fitness. In one study scientists studied the diets of 361 living mammals and 50 of these species had an appendix. By plotting these 50 mammals on an evolutionary tree, they found that the data was so scattered that the appendix would have had to of evolved independently at least 32 times but possibly as many as 38 times. (Smith 2013). In another study it is stated that in phylogeny, the appendix or similar structures to the appendix are generally rare. It is found in certain marsupials but not other marsupials and is also missing in many other host animals. This spread out occurrence of the appendix suggest that the structure is for a specific function as opposed to a once important digestive organ.

Recent studies have been trying to identify more animals that have a cecal appendix. Besides humans and apes, animals such as rabbits, lemurs, certain types of squirrels, bush tail porcupines and mole rats also have an appendix. Although all these organisms contain an appendix, it varies amongst them drastically. By comparing the appendixes of different organisms, scientists can possibly figure out what the original function of the appendix was. The rabbit has the most prominent appendix that coincides with its already enlarged cecum. The rabbits’ appendix is said to be 3-5 times larger than the typical human appendix. Many animals’ appendixes vary in size but they can also vary in position relative to the cecum. Other animals possess an appendix but have hardly any noticeable cecum. In these animals it is thought that perhaps the appendix is somewhat taking the place of the cecum. This leads scientist to believe that possibly the appendix developed as a non-digestive organ first and then evolved to be able to ferment food. The evolution of the appendix is still not fully clear.

Because the appendix has been maintained in many species, it could possibly be considered an adaptive trait. The definition of adaptive trait suggests that the appendix could have some kind of function. Recent studies have come up with the idea that it is an immune organ. One part of the theories is that the appendix acts as a safe house for good gut flora. This could aide in digestion if needed but more so immune health. Shortly after these theories came about, scientists began to look into the idea of the appendix housing beneficial gut flora. This is especially important for the re-inoculation of the gut. In the case of diarrheal infections, which would increase the amount of bad gut flora, the good gut flora could retreat to the appendix until able to re-inoculate the gut. Recent studies in 2003 discovered that the immune system supports bio-film development in the large intestine. This was supported mainly with the fact that the two most abundantly produced molecules by the immune system also support bio-film production and are associated with the bio-films developed in the gut. This is especially important because the appendix holds a mass amount of these bacterial bio-films. Other observations that help support the theory of the appendix being a safe house is the location of the appendix. It is easily inoculated but at the same time is less likely to be infected by harmful pathogens.

The possibility of the appendix housing good gut flora is a very important idea in science related to diarrheal infections. In the case of these infections, which would increase the amount of bad gut flora, the good gut flora could retreat to the appendix until able to re-inoculate the gut. This idea has pushed scientists to research whether the appendix makes a difference in the situation of Clostridium difficile, a disease caused by a spore forming bacteria that creates infectious diarrhea. One studied showed that the appendix made no difference for this disease but there have been other studies as well. (Merchant 2011). In another study when the C. diff bacteria was introduced to the gut, the appendix housed cells that increased the production of certain toxins into the bloodstream to rid the body of the C. diff bacteria. (Barlow 2013). This research greatly impacts the possible immune functions of the appendix.

Another idea that leads to the appendix having an immune function is that it is mostly, if not all lymph tissue. In the early 1900s the appendix was found to contain a lot of gut-associated lymphoid tissue (GALT) and after the discovery of this tissue; it was proposed that the appendix had an immune function. A scientist named Ransohoff stated that the mucus of the appendix looked a lot like a lymphatic gland spread out. The appendix has been compared to the tonsils in its amount of lymph tissue present. (Shattuck 1890). The tonsils are the first line of defense against harmful ingested or inhaled pathogens. Similarly to the appendix, scientists currently do not know the function of the tonsils in their entirety. In animals with an appendix such as the rabbit, studies have shown that their appendix evolves from birth into a lymphoid tissue and resembles the gut associated lymph tissue in appearance and possibly function. In animals lacking an appendix, studies have shown that the terminal part of the cecum is rich in lymphoid tissue. This leads to the idea that the immune function carried out by this portion of the cecum is analogous with the immune function of the appendix. (Smith 2009). Either the appendix never evolved to an independent organ in these animals or the appendix was lost. Although the presence of lymphoid tissue does not completely prove that the appendix has an immune function, it is a strongly supported theory.

Even though the appendix may have a function, research shows that most humans in this day and age may not need its function. Many people have their appendix removed and have no problems. It is thought that because society in most areas has modernized medicine and sanitary practices, that humans may not need their appendix for immune function. Places where enteric pathogens are not prevalent, the appendix may not be needed. Most scientists say that it is more important to remove a bad appendix than to keep it for the supposed immune function. The reasons of modern medicine and being sanitary are also thought to be the same reasons why people get appendicitis, or an inflamed appendix. This recent development about a new environment affecting an organ is an important example of evolution. The appendix is being selected against because it is not needed or it causes problems for the human host.

Overall there is still a lot to learn about the appendix. The fact that it has evolved so many times leads to a lot of questions that have not been answered. We still do not know the original function of the appendix or for sure know the function of the appendix now. According to Smith, studies have worked with anatomical and ecological hypotheses to try and find out why the appendix evolved, but no studies have looked into whether diet, digestive anatomy or social behavior explain why the appendix evolved or was lost. (Smith 2013). Perhaps if these studies were carried out, we might learn more about the evolution of the appendix. The fact that it is considered a vestigial organ but can still cause problems such as appendicitis raises a question of whether we really want the appendix present in humans at all. Humans may not even have an appendix in years to come with some of the theories that have been mentioned. Humans may evolve to not have an appendix at all because it may not be needed to provide an immune function. What about other mammals that have an appendix? Will something occur in their environment to lead to the appendix being loss? Perhaps the appendix will just evolve to support other functions. There are still many questions to be answered about the function and the evolution of the appendix in both humans and other mammals.

References

Barlow, A., S. Muhleman, J. Gielecki, P. Matusz, S. Tubbs, M. Louka. 2013. The vermiform appendix: A review. Clinical Anatomy, 26. 833-842.

Barras, C. 2013. Appendix evolved more than 30 times. www.sciencemag.com.

Berry, R., and L.A.H. Lack. N.D. The Vermiform Appendix of man, and the structural changes there in coincident with age. From the Research Laboratory of the Royal College of Physicians of Edinburgh.

Bollinger, R., A. Barbas, E. Bush, S. Lin, W. Parker. 2007. Biofilms in the large bowel suggest an apparent function of the human vermiform appendix. Journal of Theoretical Biology, 249. 826-831.

Cupples, Upham & Company. The Boston Medical and Surgical Journal. Massachusetts Medical Society, New England Surgical Society. 122. 556.

Duke University Medical Center. 2009. Evolution Of The Human Appendix: A Biological 'Remnant' No More. ScienceDaily.

Golalipour, M., B. Arya, R. Azarhoosh, M. Jahanshani. 2003. Anatomical Variations of the Vermiform appendix in South East Caspian Sea (Gorgan-IRAN). J Anat. Soc. India 52(2). 141-143.

Merchant, R., W. Mower, A. Ourian, F. Abrahamian, G. Moran, A. Krishnadasan, D. Talan. 2012. Association between Appendectomy and Clostridium difficile Infection. J Clin Med Res. 4(1). 17-19.

Reshma, M., S. Velichety, K. Thyagarju, M. Azharuddin, K. Jyothirmayi. 2013. Morphological features and morphometric parameters of human fetal vermiform appendix at different gestational ages. Int J Anat Res.1(2). 18-25.

Smith, H.F., R.E. Fisher, M.L. Everett, A.D. Thomas, R. Randal Bollinger, W. parker. (2009), Comparative anatomy and phylogenetic distribution of the mammalian cecal appendix. Journal of Evolutionary Biology, 22:1984–1999.

Smith, H.F., W. Parker, S. Kotze, M. Laurin. 2013. Multiple independent appearances of the cecal appendix in mammalian evolution and an investigation of related ecological and a atomical factors. Comptes Rendus Palevol.12. 339-354.

Weinstein, P.D., R.G. Mage, A.O. Anderson. 1994. The Appendix Functions as a Mammalian Bursal Equivalent in the Developing Rabbit. Advances in Experimental Medicine and Biology. 355. 249-253.