Skills Practice Lab DATASHEET for IN-TEXT LAB

Name Class Date

Skills Practice Lab DATASHEET FOR IN-TEXT LAB

How Will Our Population Grow?

If you were a demographer, you might be asked to determine how a population is likely to change in the future. You have learned that the rate of population growth is affected by both the number of children per family and the age at which people have children. But which factor has a greater effect? To explore this question, you will use age-structure diagrams—also called population pyramids.

OBJECTIVES

Predict which variable has a greater effect on population growth rates.

Calculate changes for a given population over a 50-year period.

Graph the resulting population’s age structure by creating a population pyramid.

Compare the effects of fertility variables on population growth rates.

MATERIALS

• calculator or computer

• colored pencils or markers

• graph paper

Procedure

1. In this lab you will calculate future population trends for an imaginary city. To compare how fertility variables may affect population growth, each group of students will test the effects of different assumptions. Assume the following about the population of this city:

TABLE 1: ASSUMPTIONS ABOUT THE POPULATION

Half the population is male and half is female.
Every woman will have all of her children during a given five-year period of her life.
Everyone who is born will live to the age of 85 and then die.
No one will move into or out of the city.

2. Your teacher will divide the class into four groups. Each group will project population growth using the following assumptions:

TABLE 2: ASSUMPTIONS ABOUT THE WOMEN IN THE POPULATION

Group / Each woman gives birth to / While in the age range of
A / 5 children / 15–19
B / 5 children / 25–29
C / 2 children / 15–19
D / 2 children / 25–29

How Will Our Population Grow? Continued

3. Predict which of the four groups will have the greatest population growth in 50 years. Write down the order you would predict for the relative size of the groups from largest population to smallest population.

4. Table 3 shows the population of our imaginary city for the year 2000. Use the data in the table to make an age-structure diagram (population pyramid) for the city. Use the example diagram in your textbook to help you.

5. Calculate the number of 0- to 4-year-olds in the year 2005. To do this, first determine how many women will have children between 2000 and 2005. Remember that half of the population in each age group is female, and that members of the population will reproduce at specific ages. Multiply the number of child-bearing women by the number of children that each woman will have. For example, Group A will have 12,500 new births by 2005.

TABLE 3: POPULATION IN EACH AGE GROUP, 2000–2050, GROUP ______

Age / 2000 / 2005 / 2010 / 2015 / 2020 / 2025 / 2030 / 2035 / 2040 / 2045 / 2050
80+ / 100+
75–79 / 500
70–74 / 600
65–69 / 700
60–64 / 800
55–59 / 900
50–54 / 1,000
45–49 / 1,250
40–44 / 1,500
35–39 / 2,000
30–34 / 2,500
25–29 / 3,000
20–24 / 4,000
15–19 / 5,000
10–14 / 6,500
5–9 / 8,000
0–4 / 10,000
Total / 48,350
Females that give birth
New births

Note: Data shown above for Group A only.

How Will Our Population Grow? Continued

6. Fill in the entire column for the year 2005. Determine the number of people in each age group by “shifting” each group from 2000. For example, the number of 5- to 9-year-olds in 2005 will equal the number of 0- to 4-year-olds in 2000.

7. Calculate the total population for each five-year period.

8. Repeat the process described in steps 3–8 for each column, to complete Table 3 through the year 2050.

Analysis

1. Constructing Graphs Plot the growth of the population on a line graph. You may want to use a computer to graph the results.

2. Constructing Graphs Make a population pyramid for the population in 2050.

How Will Our Population Grow? continued

Conclusions

3. Evaluating Data Compare your graphs with the graphs of the other three groups. Were your predictions correct?

4. Drawing Conclusions Which variable had a greater effect on population growth—the number of children each woman had or the age at which each woman had children?

5. Interpreting Information Did any of the groups show no growth in the population? Explain these results.

Extension

1. From the age-structure diagram in your textbook, what would you predict to happen to the U.S. population in the next 20 years? in the next 50 years? What parts of the age structure are most important to these predictions?

Holt Environmental Science 20 The Human Population

TEACHER RESOURCE PAGE

Skills Practice Lab DATASHEET FOR IN-TEXT LAB

How Will Our Population Grow?

Teacher Notes

TIME REQUIRED Two 45-minute class periods

SKILLS ACQUIRED

Constructing models

Identifying and recognizing patterns

Interpreting

Organizing and analyzing data

Predicting

RATING

Teacher Prep–1

Student Set-Up–2

Concept Level–3

Clean Up–1

THE SCIENTIFIC METHOD

Test the Hypothesis Procedure, steps 3–8

Analyze the Results Analysis, questions 1–2

Draw Conclusions Conclusions, questions 3–5

MATERIALS

The materials on the student page are enough for a group of 3 to 4 students.

You may want to set up a computer, if available, for the students to use to graph their results.

MISCONCEPTION ALERT

To complete this lab, students must understand and accept the assumptions given in step 2 of the procedure. Review these assumptions for each group of students. Note that these assumptions are unrealistically simplified for the sake of modeling. Check that students are able to identify the variables being tested by each different scenario (number of children/woman and age of reproduction).

Students may need extra help understanding how an age-structure diagram is structured. Have students look closely at the example diagrams. Emphasize the division between left and right for gender, and explain that each diagram represents a cross-section of the population at a single point in time (for example, one census year). Ask students questions about sample diagrams to check understanding

How Will Our Population Grow? continued

TIPS AND TRICKS

Demonstrate the method of “moving up” age groups to fill in each new column in the tables, and calculating new totals and births for each period of time. Use the sample answers in the table as a starting point. Test student understanding of the procedure by asking questions such as: “If there are 5,000 twenty- to twenty-four-year-olds in the year 2010 and each woman in that age group has three children, how many zero- to four-year-olds will there be in the year 2015?” (7,500). Students may need extra help understanding age-structure diagrams.

Name Class Date

Skills Practice Lab DATASHEET FOR IN-TEXT LAB

How Will Our Population Grow?

OBJECTIVES

Predict which variable has a greater effect on population growth rates.

Calculate changes for a given population over a 50-year period.

Graph the resulting population’s age structure by creating a population pyramid.

Compare the effects of fertility variables on population growth rates.

MATERIALS

• calculator or computer

• colored pencils or markers

• graph paper

Procedure

TABLE 1: ASSUMPTIONS ABOUT THE POPULATION

2. Your teacher will divide the class into four groups. Each group will project population growth using the following assumptions:

TABLE 2: ASSUMPTIONS ABOUT THE WOMEN IN THE POPULATION

Group / Each woman gives birth to / While in the age range of
A / 5 children / 15–19
B / 5 children / 25–29
C / 2 children / 15–19
D / 2 children / 25–29

Name Class Date

How Will Our Population Grow? Continued

Answers may vary.______

TABLE 3: POPULATION IN EACH AGE GROUP, 2000–2050, GROUP ______

Age / 2000 / 2005 / 2010 / 2015 / 2020 / 2025 / 2030 / 2035 / 2040 / 2045 / 2050
80+ / 100+
75–79 / 500
70–74 / 600
65–69 / 700
60–64 / 800
55–59 / 900
50–54 / 1,000
45–49 / 1,250
40–44 / 1,500
35–39 / 2,000
30–34 / 2,500
25–29 / 3,000
20–24 / 4,000
15–19 / 5,000
10–14 / 6,500
5–9 / 8,000 / 10,000
0–4 / 10,000 / 12,500
Total / 48,350
Females that give birth / 2,500
New births / 12,500

Note: Data shown above for Group A only.

Name Class Date

How Will Our Population Grow? Continued

7. Calculate the total population for each five-year period.

8. Repeat the process described in steps 3–8 for each column, to complete Table 3 through the year 2050.

Analysis

1. Constructing Graphs Plot the growth of the population on a line graph. You may want to use a computer to graph the results.

2. Constructing Graphs Make a population pyramid for the population in 2050.

The shape of age structure diagrams for groups A–D may vary.

Name Class Date

How Will Our Population Grow? continued

Conclusions

3. Evaluating Data Compare your graphs with the graphs of the other three groups. Were your predictions correct?

The graphs should show population growth. Group A should have the greatest _

population growth. Students should note whether or not their original prediction

was correct.______

4. Drawing Conclusions Which variable had a greater effect on population growth—the number of children each woman had or the age at which each woman had children?

The number of children per woman had the greatest effect on population ______

growth. The age of reproduction was also important but had a lesser effect.____

5. Interpreting Information Did any of the groups show no growth in the population? Explain these results.

No. All groups showed some growth because the population started out “bottom

heavy” and people were still having some children. Groups C and D would ____

eventually show zero growth.______

Extension

If current trends continue, and without considering immigration, the U.S. _____

pyramid will become more evened out as current generations age. The “bulge” _

of middle-aged people will move into older brackets (but eventually shrink due _

to natural deaths). The lower levels will slowly get smaller relative to the upper _

levels, making the pyramid more “top-heavy.” Within 20 years, the age______

structure will be somewhat evenly distributed. Within 50 years, the average ____

person will be much older.______

Holt Environmental Science 58 The Human Population