Parasites and their Virulence
Why do some parasites kill the host they depend upon while
others coexist with their host? Two prime factors determine parasitic
virulence: the manner in which the parasite is transmitted, and the
evolutionary history of the parasite and its host. Parasites which
have colonized a new host species tend to be more virulent than
parasites which have coevolved with their hosts. Parasites which are
transmitted horizontally tend to be more virulent than those
transmitted vertically. It has been assumed that parasite-host
interactions inevitably evolve toward lower virulence. This is
contradicted by studies in which virulence is conserved or increases
over time. A model which encompasses the variability of parasite-host
interactions by synthesizing spatial (transmission) and temporal
(evolutionary) factors is examined. Lenski and May (1994) and Antia et
al. (1993) predict the modulation of virulence in parasite-host
systems by integrating evolutionary and transmissibility factors.
INTRODUCTION
Why do certain parasites exhibit high levels of virulence within
their host populations while others exhibit low virulence? The two
prime factors most frequently cited (Esch and Fernandez 1993, Toft et
al. 1991) are evolutionary history and mode of transmission.
Incongruently evolved parasite-host associations are characterized by
high virulence, while congruent evolution may result in reduced
virulence (Toft et al. 1991). Parasites transmitted vertically (from
parent to offspring) tend to be less virulent than parasites
transmitted horizontally (between unrelated individuals of the same or
different species). Studies in whi...
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...gy determine the direction of the modulation.
The development of an inclusive, accurate model has significance
beyond theoretical biology, given the threat to human populations
posed by pathogens such as HIV (Gibbons 1994). Mass extinctions such
as the Cretaceous event may have resulted from parasite-host
interaction (Bakker 1986), and sexual reproduction (i.e. recombination
of genes during meiosis) may have evolved to increase resistance to
parasites (Holmes 1993). Parasitism constitutes an immense, if not
universal, influence on the evolution of life, with far-reaching
paleological and phylogenetic implications. A model which synthesizes
the key factors determining parasitic virulence and can predict the
entire range of evolutionary outcomes is crucial to our understanding
of the history and future of species interaction.
On an endless road of meadows and half collapsed barns exists a quaint town living its motto “The City of Progress”. Enterprise, Alabama is stuck between miles of bleak pastures and feeding cows, but the peanut factory overwhelms your every breath. The monotonous drive does have a reward, and it can only be found hiding in a valley of small stores and baptist churches on downtown’s main street. It is a statue that reminisces this town’s story of triumph over its struggling economy during the decline of cotton. Sculpted from stone, a woman is presenting a boll weevil in honor for its efforts in destroying the crop, cotton, Enterprise, Alabama’s main economic source.
Colonial living in the seventeenth and eighteenth centuries in the New World was both diverse and, in many cases, proved deadly through such avenues as disease, Native American attacks, a lack of proper medical treatment, and disastrous weather conditions. Even through all of these hardships, the first colonists persevered, doing their best to see the blessings in their lives and create a better life for their children through all of the uncertainties. Nothing, it seems, in the original colonies was set in stone except for the fact that they never knew what the next day would hold in store. Everything, even small mishaps, had dramatic impacts on the social, economic, and political aspects of their lives. These circumstances, however, were more strongly influenced by geography than class position, unlike what many were used to in England. How population, economics, disease, and climate played into the social conditions of early colonists is truly a story for the ages. Whether people were seeking land, religious freedom, or money and profits, everyone worked to a certain extent just to survive, let alone thrive, in the wilderness that was North America at that time.
When i Was at the mosque outside on the court while i was playing a 3 on 3 basketball game. And the teams was me, bosh and Salah vs Abu, Sunny and Musa. We started to play, and my team was down by 8 points. So i was kind of mad at my team that we was down by so much. So i told them let me take over and try to get us back in the game. So they let me take over and we went on a 7-0 run and out of nowhere we was only down by one point. Then we made a turn over, then they got the ball and they passed it to abdi. And abdi got through his defender and bosh stepped up and tried to block his shot but he head faked bosh and i step and try to block his shot and i jumped up tried to block his shot and my knee cap moved out of
Darwin: A Norton Critical Edition, Second Edition ; ed. by Philip Appleman; copyright 1979, 1970 by W.W. Norton & Company, Inc.
Even if we take the maximum amount of precaution and try to keep the house and office clean, as time passes by pests do try to enter the house and bother us and create embarrassment for us. Pests can sometimes be very bothersome, and they can also be the root for health hazards in the family and among the office staff. It is beyond our control to keep them away from our homes and office as they find a way to get in and dwell inside our buildings. There are so many different types of pests, and the building can be infected by more than one type of pest at a time. There are different methods to control each type of pest, and it is not possible for us to control it all by our self. Moreover, we will never be able to manage it as good pest control service professionals as they have specific equipment and chemicals needed to remove the pests.
Merriam-Webster defines ‘parasite’ as ‘an organism that lives in or on another organism and benefits by deriving nutrients at the host 's expense’.
Dr. May Berenbaum, an entomologist at University of Illinois, has conducted over 40 years of research on parsnips and the parsnip web worm. During her lecture on March 22nd, she explained how parsnips are invasive weeds that are full of toxic furanocoumarins. Interestingly, the parsnip webworm only eats the parsnips and is able to process the toxin very well. The interactions between the web worm and parsnips cause the parsnips to select for plants with a higher amount of furanocoumarins in order to defend themselves from the worms. When the worms are not there, i.e. in New Zealand, the parsnip plants grow taller and develop more ways to attract pollinators, and they do not put energy into having as many furanocoumarins
The experiment was made to figure out how mealworms react to different temperatures and which environment the worms liked better. The data and results of this experiment revealed that most of the mealworms prefer colder environments instead of hotter ones. Four out of the six mealworms prefered the cold over heat. The cold areas are better for mealworms because the worms are nocturnal, which means these worms prefer cooler and darker areas. In the beginning of this experiment most of the mealworms wouldn't move very much and would stay put in the center of the container. The mealworms were distracted by trying to escape, and there were some small crumbs in the container that must have also distracted the worms. The conclusion of this test on
Hi I’m Mallorie, I’m 31 years old and this is My Arthritis Story. In the winter of 1995 at the age of 10 I came down with one of the many cases of strep throat. I started getting fevers and complaining of joint pain on a regular basis.
The first practice hit you hard we started off with sprints and that was awful people throwing up all around me and I can’t catch my breath but you keep pushing it. I think that was the turning point for me I knew that a lot of people looked at me like small kid that shouldn’t play but after beating them in sprints they saw I was not going to give up. Later on that season it was our 4 game in the season we were going up against Carbondale and we are only up by 6 on defense one of our players go down. I just got off the field on offense they said we need someone I ran to them said I will go in they gave me the nod. When I got on the field it was strange because I never played defense at the time I was just thinking just hit the kid with the ball and you will do fine. The ball snapped so I started back peddling and watching the line men to see if they fire off the line if so it was a run if they backed peddled it was a pass. They fired off the line it was a run so my next thought was where but at soon I was thinking that I saw the running back was coming my way so pushed the receiver off me so it was just me and him. It happen so fast the guy and try to make cut outside but I manage to stick my foot in the ground change direction to tackle him. When I looked up at the time
I almost fell off a cliff on the side of a mountain. I was in Pitkin, Colorado, on a camping trip during the summer of 2009. The trees were green, the air was fresh so were the lakes, rivers, and ponds were stocked with fish and wildlife was everywhere. Usually, on these camping trips, I would be accompanied by a large number of people. However, this time, it was just my parents, my three brothers, and my two sisters. I was almost 12 years old at the time and having three older brothers made me very competitive. Naturally, when my family decided to climb one of the mountain’s which were around us, I wanted to be the first one to reach its peak.
“Hike” it was 5th grade recess and we were playing football. It was a beautiful August day, sunny and eighty five with a cool breeze. We were playing in the parking lot of the Oyster River Middle School. There were about twenty kids playing. Nobody had a certain route, we would just try to shake free and lose the defender as they looked for a pass from the quarterback. I was playing receiver. We all lined up at the line of scrimmage with the quarterback in the middle. I ran my post route that was already in my head. I was off and out into my route, sprinting straight and then a quick turn toward the school. Then, before I knew it, I was on the ground and so was someone else three feet away. I had ran into them. When I fell, I had
In middle school I was diagnosed with a disability with the way I expressed myself through writing. Ever since, I have gained multiple values and learned several lessons about self confidence. I was taught to push past my limits, in order to be successful in reaching my goals along with my dreams. Today I am a senior in high school who was once thought to struggle, but was able to succeed beyond expectations. To some, a disability may seem like a setback from achieving goals, but to me I used it as a challenge for myself. I accepted myself for who I was and looked at my disability as a unique trait of mine. I was able to provide a message to others that anything you set your mind to is possible with dedication and hard work. It might take
Thesis: Biological Warfare is morally and inhumanely wrong, It is the wrongful killing of men, women, and children. It should be stopped no matter what the circumstances are.
When I was 7 i burned my leg on a four-wheeler muffler. When I ran back in my house to show my dad the skin was already ripped of and the meat in my leg was showing. When I put water on it to clean it it started to gush out blood. I had to go to the hospital and get it fixed cause it was burnt bad. And I didn't have to go to school the next day cause I couldn't get it hit or it would start to gush out blood again.