Human Population – Changes in Survival
The survival rate of humans in North America has increased significantly in the past one hundred years. Improved nutrition, preventive medicine, lifestyle changes, and new technologies are a few of the reasons for this improved life expectancy. Increasing life expectancies have had an impact on population growth rates. Put simply, there are more of us and we are living longer. In Rome during the first to fourth centuries, life expectancy was about 22 years at birth. Today life expectancy is approximately 75 years at birth in North America. Of particular note is the decline in infant and youth mortality in North America during the past one hundred years.
As more humans are living longer lives, they are placing additional and unique demands on the environment. With more babies surviving into adulthood, there are more potential parents, so that even if each adult female decides to have only two or three children, the sheer number of parents having children guarantees population growth. With the increased number of adults surviving to old age, environmental and social issues become increasingly important. The elderly must live in a clean environment, since they may be more vulnerable to pollution and environmental hazards. On the other hand, since retired adults often require social services and an income, many economists believe that an increase in population is necessary, to provide workers that can support those who have retired. But it is clear than an increased population places increased stress on an often overburdened environment. Thus, some type of balance between environmental and economic interests must be reached when dealing with population issues.
Activity and Procedure
You will obtain two sets of data, giving numbers of deaths in your community by age. The first set, representing vital statistics of your region in pre-1900 times, can be obtained from one or more cemeteries or by some online sleuthing, or a combination of both. (Some cemeteries have collected all the information from tombstones and have it recorded in their office. Local libraries often have this information as well.) The second set, representing current mortality figures, can be obtained from the obituary section of your local newspaper or the cemetery as well. Online resources include www.findagrave.com, www.ancestry.com, www.obituaries.com or www.legacy.com. These are helpful, but remember to focus on your local area. A quick online search of the Orange County Register found 55 obituaries from just last week, so they are not hard to find.
Print out copies of each of the three data sheets, 9.1, 9.2 and 9.3. You will record your data on 9.1 and 9.2 and make a graph of your results on 9.3. 9.1 is for 100 males and 100 females who died prior to 1900, and 9.2 is for your record of 100 males and 100 females who died in the last five years. So you need to find age-of-death information for a total of 400 people.
It is okay to work with one other student to obtain data for this lab assignment, but no more than one. Each of you should find 200 age-of-death items, and data can be combined to make the total of 400 needed. Combining data is acceptable but each student must make their own graph and draw their own conclusions. If you are doing it alone, find all 400 age-of-death items yourself. All you need about each person is their gender and age at death, so even though you are gathering a lot of data it isn’t difficult and goes quickly.
As you acquire your data, write it in to the appropriate rows under the “number that died” column on the correct data sheet. For example, if you find out that Male A died prior to 1900 at age 62, enter one tally mark on the left side of the “number that died” column in the “60-64.99” row of Data Sheet 9.1 If Male B was 3 years old when he died prior to 1900, enter one tally mark in the “number that died” column of the “1-4.99” row of Data Sheet 9.1 . Once you have data from 100 males, stop your count and add up the number of tally marks in each category. Write that number on the right side of the row and calculate the percent surviving.
The percent surviving is simply the difference between the number that died in each category and 100. This is why it works best if you have 100 entries for each column. As the number surviving gets smaller, it will be the difference between the number who died and those remaining. Start at the top and work down – this is why you have to wait until you have all the data you will get before you do anything with the percent surviving. Remember this is a cumulative number – with each death, the % surviving decreases. By the last one the percent surviving will be zero, because everyone has died.
When you have completed the data gathering and calculated the percent surviving in all four of the categories, plot the data on the graph using Data Sheet 9.3. (If you have been working with someone else to gather data, you are now done with collaboration. Each individual should make his/her own graph and analysis.) You should have four lines, one for each of the categories (females who died before 1900, males who died before 1900, females who died in the last five years, males who died in the last five years). Make the lines four different colors so it will be easy to tell them apart.
Now you are ready to analyze your data. What accounts for the differences in the four curves? What do you think these curves would look like in the next century? How would the percent surviving change? Why would it change? Answer each of these questions and comment on your results.
When you are done, simply scan your three completed data sheets and email them to me along with the analysis of your graph and comments. You could also submit electronically to the dropbox.
Value = data tables 10, graph 20, answers to questions 10
Adapted from Exercise 9 (pp. 71-78), Human Population – Changes in Survival in Field and Laboratory Exercises in Environmental Science, 7th edition, by Eldon Enger and Bradley Smith, McGraw Hill, 2000.
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