Bios 101 Demography Lab Report

Melissa Morales
Bios 101
Spring 2013

Demography- Human Life History

Introduction

Demography is the study of human populations. It studies the size, composition and distribution of a population, and the process through which a population changes. Demography allows us to track changes over time and to depict how different periods in history change population dynamics. Births, deaths, migration and emigration, jointly produced the change within a population (Biological Science). Demography is also a central component of social contexts and social change. Patterns of survival vary depending upon the environment. Age is also an important component for many populations because fecundity and survivorship frequently vary with age. Humans are one species whose fecundity and survivorship are affected by age and the environment. One way that biologists attempt to distinguish patterns in survivorship rates is to use a life tables. Life tables permit them to keep track of how long different parts of the population have lived. A life table can also be used to predict the probability of the survival of an individual at any given time interval (Biological Science).
A cemetery is an excellent place to study human demography. Gravestones are marked with the date of birth and date of death of a deceased person. From this information one can calculate death rates and draw survivorship curves for the “population”. A survivorship curve is a graphical representation of the chance that an individual will survive from birth to any age (Biological Science). By comparing and contrasting survivorship curves for different time periods, one may look for historical trends in demography over a period of time.
Methods
In this investigation, data was collected from a local cemetery. Information was recorded information from 50 headstones, where the individual was born between 1870 and 1930. The dates of birth and dates of death were recorded for each headstone. The headstones were randomly chosen from any area in the cemetery. Then the age at death was calculated for each of the 50 individuals. The data was then used to create a survivorship curve.
Results
Part 1: Fecundity

Part 2: Mortality x | D(x) | S(x) | l(x) | 0 | 0 | 50 | 1.0 | 1 | 5 | 45 | 0.9 | 2 | 3 | 42 | 0.84 | 3 | 7 | 35 | 0.7 | 4 | 5 | 30 | 0.6 | 5 | 4 | 26 | 0.52 | 6 | 11 | 15 | 0.3 | 7 | 7 | 8 | 0.16 | 8 | 7 | 1 | 0.02 | 9 | 1 | 0 | 0 |

x= age intervals of 10 years (1-10, 11-21…etc. ending at age 98)
D(x)= number of individuals dying at that age
S(x)= number of individuals alive during that interval

Discussion A survivorship graph shows, which age categories, are most likely to die, in that environment. The overall shape provides a clue about life history strategy (Type I, II, or III). This data was collected from a subset of human population and may have particular biases depending upon social class, religious traditions, and economic factors. We assumed that all the individuals had similar living situations. According to the data, more individuals died between the ages of 55-65. Based on the demographic data from this lab, multiple conclusions may be drawn. Living conditions were probably far worse in the past. This causes death and birth rates to go down because of disease. Which causes the population size to decrease. There might have also been diseases affecting older people, which could explain why that range of ages had the most individuals dying at that age.