Co Evolution Of Humans And Disease Organisms

Co Evolution Of Humans And Disease Organisms Co-evolution is a situation where two or more species influence each others evolution reciprocally by applying selective pressures on each other. Genetically speaking, co-evolution is the change in genetic composition of one species in response to the genetic change in another. This can lead to evolutionary arms races, a classic example being the interaction between plants and insects. The development of a gene for chemical defences that is harmful to the insect by the plant will put a pressure on the population growth of the insect, and the insect will try to overcome this by evolving something to detoxify them, the plant will in turn evolve a stronger defence and so on, without either side winning (Ridley 2004). There are different types of interactions between organisms (Maynard Smith 1998). Among some are: Competition, where 2 species compete for a limited amount of a common essential resource and one or the other will be eliminated. For example, lions and cheetahs both feed on similar prey, so they are negatively affected by each other because they will have to compete for food. Mutualism, where the presence of one species stimulates the growth of another, and both sides benefit from the relationship, such as animals like cow and bacteria within their intestines. Cows benefit from cellulase produced by bacteria to help digestion while bacteria benefit from having nutrients supply from the cows. Parasitism, host-pathogen co-evolution, interaction between humans and disease organisms is an example of this, where a parasite benefit from its host at the cost of the host. In the mid-nineteenth century, Charles Darwin and Alfred Russel Wallace determined the mechanism of evolution as natural selection. Species and population do not remain fixed, but they change over time. Individuals of a same species show differences in phenotype, such as difference in height, colour, or defences against enemies. These can be passed on through generations. In a community, members of the same species will need to struggle for limited resources and avoid predators for survival. Those with an advantage in phenotype will survive better and therefore be able to reproduce more successfully. One way to recognize natural selection in a population is by using the Hardy-Weinberg equilibrium to measure the allele frequencies and genotype frequencies, on the assumption that it is an ideal population with large population size and random mating, lack of mutation and migration. There are three main types of selection: Directional selection, where the phenotype at one end of the distribution is selected for and the other end selected against. Stabilizing selection, where the intermediate phenotype is selected for while those at both extremes are selected against. Disruptive selection, where the phenotypes at both extremes are favoured simultaneously. In addition to natural selection, other factors that could alter allele frequencies are like mutation, migration or genetic drift that might eventually lead to speciation, which is the formation of new species (Klug, Spencer et al. 2007). Disease organisms are called pathogens, causing diseases by infecting or infesting another organism. They are often described as parasite, because they benefit from living in or on a host, at the cost of the host and can be anything from microorganisms such as bacteria and viruses to parasitic worms like tapeworms. To discuss the interaction between humans and disease organisms, we first have to look at how humans protect themselves against infection. The first line of defence of humans against pathogens is physical barriers. The intact skin of humans serves as an impenetrable barrier to pathogens and the acidity of sweat also hinders growth of bacteria. However, pathogens can still get inside the human body and this is where the immune system comes into play. There are two mechanisms of the immune system, namely the innate immunity and the adaptive immunity. Innate immunity is the inborn ability to defend ourselves without prior learning experience and this includes phagocytes such as monocytes and neutrophils where they can eat up the pathogens, and inflammatory cells such as eosinophils and basophils that trigger local inflammation at the infection site. On the other hand, adaptive immunity is the immune response that needs to be acquired through experience and it has exquisite specificity and immunological memory. The cells working under adaptive immunity are like cytotoxic cells that kill infected cells and B cells that produce antibody to destroy pathogens. On the timeline of evolution, humans, or Homo sapiens have only been around for less than 2 million years, while worms have been around for about 750 million years. The complexity of the innate immunity in humans today is due to evolution as time passes and more species of pathogens appeared, because only the fittest individuals survived the infection to reproduce and pass on their genes to the next generation. Innate immunity provide immediate defence against infection but it only recognises prominent differences between own cells and the pathogens, therefore responding to pathogens in a generic way. Thus, innate immunity works closely together with adaptive immunity which can give long term specific immune response due to memory cells. For example, immunity for malarial parasite will not give immunity for bacteria that causes tuberculosis (Davey, Halliday et al. 2001). Exposure to a certain pathogen in varying degrees also has affect on the genetic evolution of the immune system. One example is a cluster of genes that plays an important role in the recognition and presentation of non-self antigens to the cells of the immune system called the HLA (human leucocyte antigen), also known as major histocompatability complex (MHC) has been found to have associations with diseases like leprosy and tubercolosis (May and Anderson 1983). In a human population exposed to more of the diseases shows a higher diversity on the HLA genes. Disease organisms have different generation times. For example, the bacterium Escherichia Coli can reproduce in just twenty minutes under ideal circumstances, while the HIV (Human Immunodificiency Virus) can generate 10 billion new virus particles in a day. So in the course of the humans life, these pathogens can go through hundreds and thousands of generation, evolving to become better adapted and acquiring counter-defence to the humans immune system. Some important features of the co-evolution of humans and disease organism arise from this huge difference of reproductive rates. Pathogens usually possess certain adaptations to resist humans from trying to remove them and they are very much dependant on humans as their hosts for essential resources to survive, grow and reproduce. They must be able to find a new host before their current one dies or make their transition by means of vector species. The activity of the pathogens will to some extend reduce the fitness of humans or even kill them. There is a varying degree of harm that a pathogen can cause to humans, and this property is called virulence. For the same species of pathogen, some individuals might be totally unaffected by it while some might get infection that could be mild to serious or even killed by it. Virulence of one pathogen can be measured as the percentage of infections that leads to death. The bacterium Vibrio cholera was one the most virulent human pathogens, with a virulence of 15 percent until the appearance of HIV, which has a virulence of over 90 percent, meaning that 90 percent of infected people die (Davey, Halliday et al. 2001). There are different phases in which a disease organism can adapt to its host. The first phase being accidental infection, that is the first contact of the pathogen with a new species of host. Many human diseases are caused by pathogens that infect animals such as rabies, SARS and bird flu. Host changes are promoted by frequent contact between humans and animals such as keeping a pet. The second phase is the evolution of virulence after the pathogen has successfully invaded a new host. In this phase evolution of virulence happens rapidly because the pathogen is not be well adapted to the new host and will try to overcome the immune response by the host. The third phase occurs the pathogen has been persisting in the new host for some time and tries to reach an optimal virulence. Virulence that is too high either kills the host too quickly resulting in less time to reproduce successfully , reduce the chances of the host interacting with other hosts therefore reducing transmission or ind uces an immune response that react too strongly, while mildly virulent strains will be cleared by the immune system too quickly (Stearns and Koella 2008). An example of co-evolution between the immune system of humans and disease organism is shown in flu virus. When a large proportion of the population has developed immunity to a certain strain of flu virus, the spread of the virus will be prevented until it has evolved by mutation or re-assortment. This is called antigenic drift, where a variety of strains are created until one can infect people who are immune to the pre-existing strains. If a virus is produced that has entirely new antigens, everyone will be susceptible thus causing a major pandemic. Possibly one of the best-known cases for co-evolution of humans and disease organisms is the evolution of humans for the sickle cell trait to protect against severe malaria. Sickle cell disease is caused by a change in shape of haemoglobin, causing red blood cells to be distorted and encounter problems when passing through blood capillaries. Homozygous individuals do not survive for long and rarely reproduce while heterozygous individuals produce sickle shaped red cells and normal ones but barely develop any symptoms of the disease. One would assume that the allele frequency of sickle cell would reduce in a population but this is not the case. It has been found that heterozygotes for sickle cell have an advantage over normal individuals because the sickle shaped red cells reduce the ability of the parasite Plasmodium to grow and multiply. Another example that can be given is the evolution of the bacterium such as Mycobacterium tubercolosis, which causes TB. Strains of the TB bacteriu m have evolved recently that is resistant to all drugs, namely the multi-drug resistant (MDR) strains. Depending on the changes in human population, the bacteria can change its virulence accordingly. Some pathogens are willing to trade-off virulence with transmission, keeping virulence low so that transmission between hosts can happen. However, if the host becomes abundant or the immune system is suppressed as in the case of AIDS, then the pathogen may evolve a higher virulence. Co-evolution simply means the evolution of one species in response to that of another species. However, co-evolution does not indicate dependence on one another. Humans are not dependant on parasites for survival, and the other way around. Co-evolution of humans and disease organisms has produced many fascinating variations, whether in humans or the disease organisms. The studies on this can aide us in gaining understanding of health and diseases as disease organisms remain a major cause of mortality, especially in the under-developed regions of the world.

J.R.R. Tolkien Essay -- Biography Biographies Essays

J.R.R. Tolkien Merely mentioning the name J.R.R. Tolkien conjures up fantasies. Though his trilogy The Lord of the Rings is well known, not much else is known about the man who was a scholar before anything else. It is, in fact, the cult scale popularity of the trilogy that obscures the many accomplishments that marked his life. He won an exhibition, or a middle class merit scholarship, to Oxford University in 1911. By the time he attained his bachelor’s degree, he was conversant in seven languages and had created another. His definitive translations of Beowulf and Sir Gawain and the Green Knight are still used in colleges today. In the end, though, it will be the popularity of the trilogy for which Professor Tolkien will be remembered. John Ronald Reuel Tolkien was born in South Africa to a rather well to do banker. His early life was comfortable if middle class, but it lasted only a few years. His father died before he was five, and Tolkien spent the majority of his remaining life in what he called "genteel poverty." His linguistic genius emerged around the age of eight while his mother was tutoring him in Greek and Latin. It was around this time that Tolkien began devising a language of his own which would later develop into Elvish--a language complete with poetry and history, but not yet a people. In 1904, his mother died, leaving him and his brother orphaned and in the charge of a Catholic priest in Birmingham. Through this priest, the direction of his life would emerge. He met his future wife in the boarding house where the priest had him and his younger brother lodged. Also while in the boarding house he merited a scholarship to King Edward VI High School with the recommendation of the same priest. In high sc hool, h... ...e form of the Lord of the Rings. The bulk of the trilogy was written during the war, though it wasn’t finished until 1949. For the greater portion of his days Tolkien was a respected philologist, a dedicated professor and tutor, and a scholar above all else. In his field, he will continue to be remembered for his influence on a generation of philologists and for his contributions such as his translation of Sir Gawain and the Green Knight. Outside that rather small circle most people will remember him as the author of a wonderful story; a few more for the language and mythologies he created. Work Cited Grotta-Kurska, Daniel. J.R.R. Tolkien: Architect of Middle Earth. Philidelphia: Running Press, 1976. Yeats, William Butler. "The Second Coming." Modern poems: A Norton Introduction. Eds.Richard Ellman, Robert O’Clair. New York: WW Norton & Company,1989. 83.

Personal Morality Essay

Introduction I would not have believed you two years ago if you told me an individual’s single decision could have such a profound effect on not only their lives but that of their family, their employer, the economy and even the world. The life we lead and the choices we make affect more than ourselves, as evident with the current economic turmoil we are in today. If a consumer would not have exaggerated their income to qualify for a mortgage they knew they would not be able to afford. If the mortgage lender would have verified the information on the application and if they found inaccuracy they would have rejected the loan instead of looking the other way; would our nation’s economy be in the situation it is today? Personal ethics, values, morals; however you wish to describe them, play a role in every single decision we make; we want others to believe we are a good person, someone that can be trusted. But as we are painfully aware not everyone has a moral compass by which they live. I believe that we are strongly influenced by our environment; I was raised by two loving parents who taught me right from wrong. I was raised Catholic and attended church every week; I was an altar boy and lector for our church; I had a positive relationship with all the clergy members I encountered and believe this too is part of my moral fiber. Although not a practicing Catholic, I do pray every day and believe in God and that we will ultimately be held responsible for our actions. Unfortunately only 63% of American children grow up with both biological parents according to a report conducted by The State of our Unions (2007). A great number of children are being raised by a single parent who themselves were raised by a single parent. I believe that a lack of a two parent household reflects the current moral climate we are in today. I will concede the fact though that just because a child is raised by a single parent does not mean that the child will lack values or morals; I have encountered several children raised by both parents that have poor social values and make poor decisions and just don’t seem to learn from them. Just recently my wife and I had dinner out and I was debating between several different wines. The server asked if I would like a sample of one of the wines to help me make my decision. I accepted the offer and enjoyed the wine so much I had two glasses of it. When I received the bill at the end of the dinner I noticed that our server only wrung up the wine sample which was at no cost and never charged me for the two glasses of wine. I told our server she had forgotten to charge me for the two glasses of wine; she seemed quite shocked and said â€Å"Oh you’re honest†. I jokingly told her that two glasses of wine wasn’t worth burning in hell for; I gathered from her reaction that most of her customers would never have said anything. I recently recounted my experience at the restaurant to friends and colleagues and I was quite surprised to learn that the majority of them said they would not have said anything; they would have paid the bill and left. I then recounted an experience I had with The Home Depot; I purchased a John Deere riding tractor several years ago while living in Green Bay. Two weeks later I received a voice mail from The Home Depot stating that they would like me to come in and pick up my tractor since it was the end of the season and they would be moving them into storage. I was quite shocked when I received the call since I took the tractor home the day I purchased it; apparently the employee that assisted me with the tractor never completed the paperwork that noted I had already taken delivery of the tractor. When I recounted this story almost all of the people said they would have told The Home Depot of the error. The consensus I gathered from both scenarios is that the tractor’s value was almost $1700. 00 where as the price of two glasses of wine was about $15. 00. For many it seems morality has a price limit. I recently took my stepdaughter shopping; she wanted to pick up a gift for a friend who had driven her to the airport. Samantha picked out a necklace for her friend and also found a couple of pairs of earrings for herself. Samantha and I met my wife for dinner after shopping and while showing my wife what she purchased for her friend she noticed that she was not charged for a pair of the earrings. She asked my wife and I what she should do, and I used this opportunity as a teaching moment and asked her what she thought she should do. She said she didn’t know, and I told her that she was an adult and although being an adult is not always easy that she would have to make her own decision and live with the consequences. Samantha decided she would return to the store and inform them of the error and pay for the pair of earrings. I was proud she had came to her decision but hope that the next time this happened that she would not have to ask for advice and would ultimately do the right thing Conclusion I have been instilled with what I feel is great moral character. I feel my morality is a direct reflection of the environment in which I was raised and I thank my parents, teachers, family and friends for shaping the man I am today. I wish everyone could have had the fortunate experience I had growing up; I believe that the world would be a much better place to live if we all had a working moral compass.

Gun Control - 1095 Words

Gun Control: The Battle Rages On Abstract This paper discusses and is centered around the on-going debate over gun control, I directly address how each major political party views this subject and what I believe the United States Government should do to be able to best combat this tremendous issue. I use research from multiple sources that contrast each side of the argument and give an overall insight into the world of modernized gun control. Gun Control: The Battle Rages On With the Second Amendment giving American citizens the rights to bear arms, and approximately fifty percent of Americans owning some form of a firearm, issues involving the ownership and possession of guns have led to heated debates in American society. Most†¦show more content†¦They take the term in an individual sense, therefore giving the individual the right to own and possess arms (Maguire, 1994, p. 58). The new laws and regulations being advocated by pro-gun controllers give those in opposition the feeling that their rights involving guns are slowly being taken away, and worry how far it will go. Having stated all of this information, it is imperative to choose what side of the gun control fence you stand on. Are you for gun control, or against it? A lot of the time people decide hastily without looking at both sides of the argument, or doing their own individual research before coming to a logical conclusion. When it comes to discussing how each major political party views this topic, it is often times easy to determine what position you defend or take on the issue because of the party you typically side with. The Democrats for instance often coincide with pro-gun control which not only favors strengthening gun control to reduce violence but also to reauthorize an assault weapons ban and close the gun show loophole that has been prevalent, especially in recent memory. 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