Ecology Manuscripts Essay

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Life Table

Sean Anselmo
Ecology 201
2-25-13

Abstract Life Tables are one way to express how populations of organisms can vary over an extended period of time. The rationale of this experiment is to figure out if the hypothesis stating that survival rates in human populations are inclined more by environment in which the populations occur than by their source. There are many different ways to accumulate data to use to interpret into a Life Table. There are 3 different Life Curves that are known as Type 1, Type II, and Type III. The data that was used for this experiment was collected in a cemetery here in McLean County, Illinois, USA and Russel, New Zealand. The residents of both areas can be traced back to the British Isles, which means they all originated from the same area. There are two different methods used in this experiment: New Zealand Data and Bloomington Data. The New Zealand Data was collected by an outside source, while the Bloomington Data was collected by the students in this experiment. Statistical Analysis is used to test hypotheses about the influence of the environment on the two populations of McLean County and New Zealand. A test that is used is the Kolmolgorov-Smirnov Test also known as the K-S Test. Introduction Life tables provide an incredible amount of information. Typically data collected for the creation of life tables are taken from a group of individuals born around the same time or a representative sample of individuals of all ages. Life tables can take a tremendous amount of time to build and construct so sometimes other methods are used to help estimate them, such as “age at death observed.” This is the method we used to determine our life table in this experiment. With using this method one must assume that the dead people must be a random sample, and the population must have been stable, and the age-specific mortality rate must have been constant. Although, even if all the assumptions are met, there can still be other factors that can cause a significant amount of variation, such as only certain people, of certain social classes could have been buried in this cemetery which in turn could affect how the population was exposed to certain diseases. But there are 2 main points than can be taken from a life table, mortality and survivorship curves. There are three specific types of survivorship curves: Type 1 curve is commonly seen in organisms that have high initial survivorship, but as their age increases so does mortality. Type 2 curves signify mortality is not affected by age. Type 3 curves are discovered in organisms with high mortality rates but mortality lowers with an increase in age. The two populations that were used came from the same area of origin, the British Isles. However the two populations were exposed to two very different climates, one was exposed to a Midwestern climate in the USA, which is extremes on both ends of the spectrum during one season is may be a high of 90’s into 100’s and then a month later have lows into single digits. These extreme conditions can take a major toll on a person’s physical strength. The other population was exposed to a tropical climate on the shores of New Zealand, which was mostly a warmer climate year round and they were not affected by such dramatic climate changes so therefore there was not as much of a physical strain placed on the people living there. The null hypothesis would be that the survivorship of the two populations would be the exact same since the two populations originated from the same parts of the world. But some alternate hypotheses would be: Since one population is in a warm tropical climate they may live longer because unlike the other population who is exposed to harsh and cold winters, the population in New Zealand does not have to deal with such hardships so therefore they may live longer. Although another hypothesis could be that because the population living…