APES: Cemetery Lab
* adapted from versions by Jim Serach and Jesse Klingebiel
Introduction
A population can be generally defined as a group of interbreeding individuals of the same
species occupying a given area at a given time. Populations are dynamic entities that undergo
change over time. Populations grow and shrink and the age and gender composition also change
through time and in response to changing environmental and social conditions. Population
ecology is the study of populations and their changes over time. One technique used to study
population ecology is the construction of life tables.
A life table uses information about age- and gender-specific mortality rates to determine patterns
of survivorship and life expectancy. Life tables can be constructed in two ways. The first way is
to study a cohort, a group of individuals born at roughly the same time, from birth to death.
Cohort studies are impractical for studying changes in the human population because humans
tend to live for a relatively long time.
A more practical approach for studying human population ecology is to construct a static life
table using data from cemeteries, historical documents, or even obituaries. Using this technique
one may sample a given population at a snapshot in time. The data from the life tables can then
be used to construct survivorship curves and examine age-specific mortality classes.
Survivorship curves generally fall into one of three typical shapes (Figure 1). Organisms that
exhibit Type I survivorship curves have highest probability of death in old age. Species with
Type III survivorship have the greatest probability of death at young ages. In other words, these
species suffer very high mortality of eggs and young. Type II survivorship is intermediate
between the others and suggests that such species have an even chance of dying at any age.
Figure 1. Generalized survivorship curves (From: http:// jan.ucc.nau.edu/.../ Lectures/lec14/lec14.htm)
Pre-lab
Since we do not have easy access to a cemetery near Trinity, your pre-lab will require that you
go out to a local cemetery and gather some data. You will need to find headstones for individuals
that were born between 1900 and 1950. Use the following data table to gather data on at least
ten headstones.
Age at Death
Birth year: 1900-1925
Males
Females
Birth year: 1926-1950
Males
Females
0-5
6-10
11-15
16-20
21
26
31
36
41
46
51
56
61
66
71
76
81
86
91
96+
Procedure
Once in class, combine your data with your classmates’ data. You should have a sample size of
at least 80 individuals. Use this data to fill in and calculate several pieces of data. Then answer
the accompanying questions.
Questions
Use complete sentences.
1. Plot survivorship curves of lx against age group. You may put all four sets of data on the same
graph. These line graphs can be used to see if the population has a type I, II or III survivorship
pattern.
2. Are there any historical factors that could affect your population? What evidence is there that
show an impact of these factors? ___________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
3. Does your data support the trend that women tend to live longer than men? Support your
statement with explanations of why or why not. _______________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
4. What type of survivorship do your curves show? Any differences between groups or sexes? __
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
5. How would your expect your data to change if we did a more recently born group of
individuals? ___________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________