Sunday, March 17, 2013
Cold Symptoms
On pages 118-119 the author talks about how the cold virus lets us move around yet it spreads to our families, friends and close relatives by triggering the sneezing symptom. Mr Paul Ewald believes that the cold virus has "hit the evolutionary jackpot" because it guarantees our mobility as well as its survival. This is because the virus needs us to survive. This goes along with big idea number one, which is the how evolution is a change in genetic makeup of population over time and so forth because the virus has evolved to ensure its own survival by inhabiting our human bodies as a host while spreading itself to others. The cold virus is not the only one who does this trick, on page 118, he describes how STDS can also be transmitted by close proximity. But unlike these two viruses, malaria actually goes for virulence because it doesn't need us to survive to ensure its survival, because it has an "evolutionary advantage to push its host towards death" This is really intriguing to know how viruses use us as hosts, but some don't needs us to survive yet others do, why do you think this happens? and what do you think is the benefit for malaria and the cold virus to inhabit? how are they similar and different? cdiaz3@students.d125.org, Carolina Diaz.
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Pathogens can select for or against traits that harm their hosts. The best interest of all infectious agents is to survive and reproduce by infecting new hosts: it determines the traits. There are three basic ways a microbe moves from one host to another: transmission through the air or physical contact, transmission through an intermediate organism, and transmission through contaminated food or water (118). Infectious agents that get transmitted through the air or physical contact of their hosts, such as cold virus, select against traits that harm their hosts because those infectious agents rely on their hosts to carry them around and introduce them to new hosts. However, infectious agents that get transmitted through an intermediate organism, such as mosquitoes, select for traits that harm their hosts because the mosquito is more likely to ingest the infectious agents and carry them to other hosts when the hosts are physically vulnerable (119). This selection of traits for survival and reproduce is related to Big Idea 1(The process of evolution drives the diversity and unity of life). Malaria and cold viruses are similar in the ultimate goal: to survive and reproduce by infecting new hosts. Also, malaria and cold viruses are similar in being under the evolutionary pressure: they have to change their traits depends on their environment. However, the ways of getting transmitted to the new hosts are different for malaria and cold virus: malaria needs the intermediate organisms, and virus gets transmitted by air or light physical contact of hosts. In addition, cold virus is not organic but a bunch of genes, but malaria is caused by plasmodium, a one-celled parasite that is transmitted by the bite of the Anopheles mosquito. Malaria is caused by four species of parasitic protozoa: Plasmodium vivax, P. ovale, P. malariae, and P. falciparum. When Plasmodium inhabit in the salivary gland of mosquito, they are transferred in human body and travel to the liver. From there, each sporozoite divides into thousands of merozoites; sporozoites attack the red blood cells. The merozoites mature into the trophozoite phase and reproduce by division; many more merozoites are released into the blood when the host cell finally ruptures. When a mosquito bites the affected person, the insect takes up merozoites, and merozoites reproduce sexually in the mosquito’s gut. As the larval parasites go through the mosquito’s gut wall and arrive to salivary glands, they can be transferred into a human body again as sporozoites.
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