Students study demographics, ecology in cemetery

By Amy Widner

Photo by submitted photo

Russellville High School seniors Grace Kellner, left, and Talley Gale, right, place flags on a grave in Oakland Cemetery to show that its information has been collected. The students were gathering the data as part of a mortality-rate study, comparing pre-1950 mortality rates to modern ones.

ADVERSTISMENT

RIVER VALLEY and OZARK AREA — What do bugs, cemeteries and antibiotics have to do with each other?

Russellville High School students in Paul Gray’s AP Human Geography class and Chuck Campbell’s AP Environmental Science class could tell you. The classes worked together on a lab that sent them to Russellville’s Oakland Cemetery for a study of mortality rates.

Perhaps the better question is: What do bugs, cemeteries and antibiotics have to do with whether you expect to live 77 years, life expectancy today, or 51 years, life expectancy in 1910, according to the Centers for Disease Control?

Campbell said there is a common graph used to explain how different species ensure enough of their young live to reproduce and continue the species: survivorship curves.

The type-three survivorship curve plunges deep, representing a large number of deaths in early life, before leveling out as age increases.

Plants do this - releasing millions of seeds, only a few of which successfully take root and grow to adulthood. So do bugs. Many baby bugs end up as dinner long before they’re old enough to be parents.

The type-one survivorship curve is essentially the opposite. It represents species like elephants, which have long gestation periods (22 months) and invest a lot of effort and parenting into few offspring. The type-one survivorship curve plunges as the species ages, with the most deaths occurring later in life.

The type-two survivorship curve is a diagonal line between the other two. Among such species, like squirrels and honey bees, death rates remain essentially constant throughout life. Hunting and disease are common causes of death.

Campbell wanted to teach these concepts as part of his unit on population, especially as it relates to ecology. He has done the cemetery lab for four years now and still remembers first coming across the idea to study survivorship curves by looking to local cemeteries.

“I found this lab where these guys were producing the different survivorship curves from mortality rates they were gathering in cemeteries, really old cemeteries, out on the east coast,” Campbell said. “I thought: ‘Human population? This applies?’ It was an eyeopener to me.”

He was surprised because humans are the classic example used to describe a type-one curve. Like elephants, humans tend to die off later in life rather than sooner. Campbellhad never thought about how disease and other factors, like the danger of childbirth for women, might have made that curve look a little different 100 years ago.

What better way for Campbell to impart on his students an ecology cornerstone: humans are part of nature, too, not above it.

“One of the things I try to do is stamp out this idea that the ‘environment’ is out there and humans are over here and we are above and separate from the environment,” Campbell said.

This was the first year for Gray’s human geography students to participate. He said it was a great exercise for them in gathering data and considering basic demographics concepts like mortality rates, infant mortality rates, fertility rates and human migration (many of the older graves were of German and Scotch-Irish origin).

Gray’s students also got to consider how different marriage customs affect demographics. In the older graves, they saw that women typically married older, landed men, and men typically had several wives, as women were much more likely to die in childbirth.

Students from four classes gathered data in Oakland Cemetery. Each team was charged with collecting the gender and age at death from 150 graves that predated 1950 and 150 graves after 1950. The teams used colorful flags tomark the graves from which information had already been collected.

Campbell chose 1950 because antibiotics became more commonly used after this time. Students entered the data they gathered in Excel spreadsheets and compared the pre-1950 graph to the post-1950 graph.

They had small notebook computers with them in the field where they could record data and look at the graphs, and then the class considered them together back in the classroom.

They looked at the data in a variety of ways: female mortality rates, rates in rural areas compared to town (which turned out to be the same) and more.

Senior Zachary Freeman, one of Gray’s human geography students, said the results were startling. The pre-1950 graph looked much more like a type-two graph: the diagonal line that shows that death rates remain about constant throughout life.

“That was the most interesting part to me, that sharp difference between our historical data and our modern data,” said Freeman, who was in charge of doing the computer work for his team. “It was an interesting exercise in teamwork, working within a larger group to do something important, like the kind of thing a census collector would actually do, not just busywork.”

Next year, Campbell hopes to find enough pre-1900 graves in the area for a good graph.Would infant and childhood mortality rates be so high that the data would resemble a type-three survivorship curve, like bugs and plants? He’s not sure, but it would be fun to find out, he said.

If anyt hing, Gray and Campbell are sure they will continue to find ways to collaborate with each other on different units, possibly including other classes like AP Statistics in next year’s lab.

Their upcoming units on agriculture would be another opportunity for collaboration, and the two said they are even considering co-teaching a class some day.

“All of this, it’s been great for the kids, and it’s been great for us, too - a new way to look at things,” Campbell said.

- awidner@ arkansasonline.com

River Valley Ozark, Pages 161 on 11/01/2009