# Predicting Human Population Change Part 1: Age Structure

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## Objective

Students will be able to collect and compile population data from online resources and predict patterns of future human population growth by comparing age structure diagrams of three different nations.

#### Big Idea

Historical trends and ecological understanding make predictions of future developments possible.

## Introduction

Thisis the first lesson of a three lesson sequence (Links to Part Two and Part Three) that asks students to collect and interpret data from multiple online sources to predict the future impact of human population growth based on current trends in three different countries.

This lesson sequence is largely independent exploration on the part of the students.  Much of the teacher's role in this sequence is to simply troubleshoot technology issues students have, clarifying instructions and guiding them in their interpretations of data.

Please Note: Access to laptop or desktop computers is essential for this activity as some of the websites have very limited mobile functionality.  You may want to plan ahead and schedule a 3 day block in your school's computer lab if you do not have a class set of computers.  It could be possible to have students use smartphones or tablets, but some of the websites have interactive components that are optimized for a desktop or laptop, so I suggest using a computer cart or computer lab if that option is available to you.

Connection to the Standards:

In this lesson, students will follow a complex, multi-step procedure, integrate multiple information resources to address a problem, develop claims supported by evidence, conduct research, and model with mathematics to arrive at a better understanding of cause and effect relationships in complex systems.

## Warm Up

10 minutes

This lesson follows the describing populations lesson and gives students an opportunity to employ the concepts and vocabulary of that lesson to predict the future population growth of three separate countries.

I begin this lesson by asking students to review their notesheet from the previous lesson's presentation.  I then ask...

• "what is an age structure diagram?" A: a visual depiction of a population broken down by age and sex
• "what information does an age structure diagram contain?" A: the sex ratio and percentage of a population in five year age groups (e.g, 0-5, 6-10, 11-15, etc.)
• "what can the shape of an age diagram tell us about the future of a population?" (Whether the population is expected to grow, remain stable, or shrink)

Once we have gone over that quick review, I ask students to choose a partner to work with and then have one partner get and set up one computer for the pair and the other partner pick up the activity instructions, the age structure diagram template, and a box of colored pencils.

## Guided Practice

15 minutes

Once students have their computers, I project my computer on the screen at the front of the room to give a short demonstration on how to use Population Action International’s Shape of Things to Come” interactive website.

First, I ask students to join me on the website and to click on the "Country Age Profiles" Tab.  I demonstrate how to choose a country by pointing my cursor and clicking on North America.  I then click on the United States to generate an age structure diagram which shows information for 1975, 2005, and projected age structure for 2025.  I make sure to warn students that going "back" on their browser takes them out of the website entirely, and show them the close button in the interactive.

I then demonstrate how to compare three countries by first clicking the "compare countries" tab.  I then click on the U.S. under the North America tab, then ask students to offer countries for comparison (in my case, soccer fanatic students shouted out "Spain" and "Brazil"... which actually turned out to be a good example of three different age structures).

I then ask students to compare these same countries and do a quick walk around the room to check that they can all do so, giving assistance where needed.  After I have confirmed that all students can use the interactive to bring up the comparison of the three countries, I ask the entire class what we can predict about these countries' future population growth based on the age structure diagrams.  This is a review of concepts discussed in the describing populations lesson.  The basic predictive shapes can be found at the bottom of the notesheet from that lesson, so I would ask students to take that sheet out and use it to analyze the age structure diagrams of the U.S., Spain, and Brazil.

In this case,

• The U.S. could be described as "stable" or "stationary" because there are roughly equal amounts of pre-reproductive and reproductive individuals, suggesting birthrates around replacement fertility.
• Spain could be described as "contracting" because the diagram is "top heavy" with much fewer pre-reproductive individuals than reproductive and post-reproductive individuals.
• Brazil could be described as "expanding" because there are more pre-reproductive individuals than reproductive individuals.  However, this would be more accurately described as a stage 2, "slow growth" age structure, especially when compared with countries that are "very young" rather than "youthful".

I then tell students that they will be choosing three different countries of their own, but that they need to be a bit more intentional than in our example because they're required to choose countries from three specific categories.

I then have them close the "Compare Countries" tab and go back to "Country Age Profiles" tab.  I click on Asia and ask them what the different colors of the countries mean.  Observant students will notice the key in the bottom right of the interactive and point out that they correspond with the categories, "very young, youthful, transitional, and mature".

I then tell students that their first task will be to choose three countries, one from each of the following categories:

• Very young or Youthful
• Transitional
• Mature

Once I have demonstrated how to use the interactive database, we are then ready to move on to the independent practice portion of the lesson where students will collect data on the countries of their choosing.

## Independent Practice

60 minutes

Student pairs are ready to work on the activity independently once they have found a country in each of the required categories:

• Very Young or Youthful
• Transitional
• Mature

Some students will be off and running and need very little help on this activity (I had one pair of students finish the entire activity in an hour), but some will need time to get familiar with the interactive database and need help interpreting the data they collect.

I move around the room for most of this time checking first that every group has selected 3 countries (I try to do this in the first 10 minutes of this section to make sure everyone is on task to complete the activity in time).  Following this initial check, I move around and routinely monitor student groups' progress and answer questions as necessary.

As they generate and sketch age structure diagrams for each individual country in the first part of the activity, they will be looking at each country's data from 1975, 2005 and the projected 2025 data.  However, it's important to point out to students that once they get to the final task of completing their detailed, comparative age structure diagram of their three countries on the separate sheet, they need to make sure they're using the most recent data (2005) and not the projected data (2025) nor old data (1975).

As they make their detailed age structure diagrams, you may want to remind them to make a key.  Some students choose to use the same colors for males and females for each country, others will choose to give each country its own color scheme.  Either approach is fine, as long as they communicate what the colors represent in their key.

## Wrap Up

30 minutes

When there are about 30 minutes left in the class, I begin to check students answers to the questions to see how they are interpreting the data.  It's helpful at this time to dialogue with the students about what their data means, as some students may still struggle with the concept that the shape of the age structure diagram is a predictive tool:

I try and make my way to each group in the first 20 minutes of this wrap up time, whether they're struggling or not, to get a sense of where the class is at in terms of having gathered all their required data and their answers to the follow up questions.

In the final 10 minutes, I go over the final two questions of the activity with the entire class:

• Which country will experience the most population growth in the future?
• Will the countries population structures become more alike or more different in the future?

For both of these questions, I ask students that volunteer answers to provide specific data from their diagram to support their prediction.  Since different groups collected data on different countries, it's helpful to have multiple groups offer answers to both questions.  If time allows, you might want to ask students to make statements about trends in their data (e.g., are countries with similar projections geographically isolated from one another or found together in particular regions?)

If any groups are not finished with this activity by the end of class, I let them know they must complete it for homework because we will be continuing to look at their countries in more detail in the next lesson in the sequence.