Demography is the branch of science that studies the changing human population. Demographers track population changes in different countries and regions. The changes are represented in graphs and tables called survivorship curves and life tables. Survivorship describes the pattern of survival in a population, in this case, humans. Life tables track groups of organisms born at the same time throughout their life span, recording how many continue to survive in each succeeding year. Survivorship is displayed through three types of curves on a graph, types I, II, and III. The type I curve, shows us a high age-specific survival probability in the early and middle stages of life, followed by a decline in survival later in life. A type I curve can typically be seen within species that produce fewer offspring, but care for them well, this is mostly viewed in humans and mammals. …show more content…
This includes birds, reptiles and many other animals. A type III curve, is characterized by a decreasing concave line. This curve shows a higher death rate early in life, if the organism survives, it has higher chances for a longer life. This is seen in small mammals and marine invertebrates. “The general shape of the survivorship curve is fixed for each species, however, the convexity of the curve is highly sensitive to environmental conditions and the genetic constitution of the population. This fact suggests that the general shape of the life table may provide information about the genetic variability in the population, the range of environmental factors that impinge on the population or the incidence of random events in the lifetimes of different individuals” (http://www.nature.com/nature/journal/v275/n5677/abs/275213a0.html) . Here, we will view the survivorship between urban and rural population’s pre and post
Patients who have died, dropped out, or not reached the time yet are not counted as “at risk.” On the other hand, patients who are lost are considered “censored” and are not counted in the denominator. The probability of surviving to any point is estimated from cumulative probability of surviving each of the preceding time intervals (calculated as the product of preceding probabilities). Although the probability calculated at any given interval isn’t very accurate because of the small number of events, the overall probability of surviving to each point is more accurate. Thus the plot of the Kaplan–Meier estimate of the survival function is a series of horizontal steps of declining magnitude which, when a large enough sample is taken, approaches the true survival function for that population. The value of the survival function between successive distinct sampled observations ("clicks") is assumed to be constant. If a patient withdraws from a study, i.e. is lost from the sample before the final outcome is observed then small vertical tick-marks on the plot indicate losses, where a patient's survival time has been right-censored. When no truncation or censoring occurs, the Kaplan–Meier curve is the complement of the empirical distribution
Rapidly evolving throughout the late Pleistocene to the early to mid Holocene, hunter-gatherer-fisher societies hunted megafauna creatures in a systematic and ethical way. When one species migrates to a different ecosystem, that species is not usually recognized as a threat to other species. Survival, during the late Pleistocene and Holocene era, was one of the most important aspects to life. Any organism, regardless of size, living within their environment had to stay alive and reproduce. During these two eras, it seems...
Some people believe that immigration in the 1900’s was a good thing, however, they would be wrong. The United States government should have restricted the immigrants around that time. Some reasons are the population, the taking of new jobs and lowering wages, and diseases spreading quickly. These all factored importantly into why they should not have been allowed in.
According to Klug, &Ward (2009), members of a certain population from another are distinguished by the presence of unique genetic characteristics. It is believed that large populations have greater diversity of alleles, compared to the small populations. In most cases, the diversity of alleles designates a greater potential for any evolution of new genes combination. This also shows greater capacity for evolution in adapting different environmental condition. On the other hand, individuals in small populations are possible to be hereditarily, anatomically as well physiologically more consistently than in large populations.
The eradication of species numbers average at a toll close to one hundred percent of earths total living creatures. “It is the Earth's most severe known extinction event, with up to 96% of all marine species and 70% of terrestrial vertebrate species becoming extinct” (Sahney, and Benton 759). Not only where marine and terrestrial species effected but this catastrophic event is the only recogni...
1. Demography is a discipline in Ecology that deals with population measures such as, age, size and overall structure are critical to demographic work. Demography is used to help understand a populations growth pattern, although not all individuals are the same age and size or have the same survival and birth rates. Demography allows for greater depth and detail of a populations structure to be characterized and analyzed.
Sigelman, C., & Rider, E. (2012). Life- span human development . (7th ed.). Belmont, CA: Wadsworth
To find out the population growth of a certain area (namely my home town of Powell, Tennessee) I visited a local cemetery to record data from the headstones. The information I collected was sex and age at death. I then charted these findings to establish the number of male and female deaths during a certain century, and the average age of each at the time of death.
Mills, Scott L., Daniel F. Doak, and Michael E. Soule. "The Keystone-species Concept in Ecology and Conservation." BioScience 43.4 (1993): 219-25. Apr. 1993. Web. 30 Oct. 2011.
When discussing each generational cohort, it is important to note that each generation lives through a “shared set of social and historical events that help form their attitudes, values, and beliefs” and Veterans, in particular, experienced several hardships (Fore, 2013). Veterans exhibit the “highest degree of respect for authority, they are loyal, and patriotic, and living through the Great Depression made them more fiscally conservative” (Fore, 2013). Many of these workers reached adulthood during or immediately following the Great Depression and two world wars. Because of growing up during such historically-significant events, “Veterans’ socialization was based on values built on structure, defined roles and responsibility, patriotism,
Population Pyramids can also be called the age pyramid or an age picture. Population Pyramids show age populations in a particular country or region. This shows how it increases or decreases and this forms the shape of a pyramid. They also use male and female pyramids to try and predict what services might be needed to help a certain age group. They can also predict when the country might be having problems based on the fertility and mortality rates of a country.
Zacherl, Danielle. “Biology 171 Evolution and Biodiversity.” National Association of Research in Science Teaching 2007 Annual Meeting, New Orleans LA. (2007):n. page. Print.
The second concepts that I am going to talk about is gerontocracy and Kubler-ross stages
In Wilcove’s article, it is examined within the 50 states the four types of animals being discussed such as mammals, birds, reptiles, and amphibians with the possibility of becoming extinct or critically imperiled determined by The Nature Conservancy (TNC). David Wilcove states that, “A total of 2,490 imperiled species, subspecies, and populations fit these criteria” (Wilcove, Rothstein, Dubow, Phillips, & Losos, 1998, p. 607). In response, within these 2,490 animals at risk the science of these problems is that their home is destroyed, and when introduced to a new environment they cannot adapt to the normal life in the same manner. Native animals cannot compete with the new species discovered and...
In every human’s life, development reflects both continuity and discontinuity. One aspect of the continuity discontinuity issue concerns whether the changes we undergo over the life span are gradual or abrupt. Continuity theorists view human development as a process that occurs in small steps, without sudden changes. In contrast discontinuity theorists picture the course of development as more like a series of stair steps, each of which elevates the individual to a new and more advanced level of functioning when an adolescent rather rapidly gains six inches in height and achieves sexual maturity. These changes may seem quite discontinuous. There are several theorists that have explored the continuity and discontinuity process.