Life tables and survival curves are important, but often difficult,
topics for students in ecology. Static life tables can be constructed
from ages at death (e.g., Dall sheep) or from snapshots of the
proportion of individuals in different age classes (age structures) at
a given time (e.g., tree-ring data). The assumptions involved in
developing life tables from these two methods differ. Ecology
laboratory courses frequently include an exercise in which students
visit a cemetery and construct a life table and survival curve from
birth and death dates recorded on tombstones, an example of the first
static method. Such labs also often ask students to compare survival
of two groups (e.g., males vs. females or people living in different
eras).
Results/Conclusions
I have redesigned my “cemetery lab” in two ways to provide a
richer set of opportunities for students to design their own projects. Now, many cemetery records are available on line and allow students to make many more comparisons than they could if visiting a single cemetery. They
can now find data from different cities, from African-American cemeteries, and from small rural and large urban cemeteries. Secondly, data from the U.S. census can also be used to develop a static life table—and I have not seen this method used in any ecology lab books. The U.S. Census data allow students to make many comparisons, including age, sex, race, urban-rural, geographic area, and era. Finally, constructing static life tables from ages at death and snapshots of age structure diagrams involve different assumptions. Therefore, students can compare life tables and survival curves that result from the two different methods and evaluate the effect of different assumptions on the resulting curves. I will provide lab handouts and samples of the results of possible projects.
