Textbook: Population Distribution and Composition | AP Human Geography - Grade 9 PDF Download

 Page 1


UNIT 2: POPULATION AND MIGRATION PATTERNS AND PROCESSES 53
UNIT 2
Population and Migration 
Patterns and Processes
Chapter 3 Population Distribution and Composition 
Chapter 4 Population Change
Chapter 5 Migration
Unit Overview
The distribution of people influences all other elements of human geography. 
Where people live, whether spread out in small communities or concentrated 
in large cities, affects how they relate to one another, what demands they place 
on the environment, and what decisions they make as a community. 
People decide where to live based on many factors. Some are physical: 
people want to be near sources of food and water and where the climate is not 
too extreme. Some factors are human: people might move to take a job or to 
be close to family.
Changes in Populations
For most of human history, women typically gave birth to many children, but 
so few children survived to adulthood that the total human population grew 
slowly. However, in the past two centuries, advances in public health, medical 
care, and the economy have enabled people to live longer. As a result of these 
new patterns, the global population has exploded. However, in recent decades, 
population growth has leveled off in many wealthy countries, such as Germany, 
South Korea, the United States.
Why People Move
People have always been on the move. Usually, they migrated by choice, wanting 
to leave a place of poverty or persecution or warfare in order to live in a place 
with economic opportunity, religious liberty, political freedom, and peace. 
In some cases, people had no choice. For example, for nearly four centuries, 
Africans were enslaved and brought to the Americas.
ENDURING UNDERSTANDINGS
PSO-2:  Understanding where and how people live is essential to understanding 
global cultural, political, and economic patterns. 
IMP-2:  Changes in population are due to mortality, fertility, and migration, which are 
influenced by the interplay of environmental, economic, cultural, and political 
factors. 
SPS-2:  Changes in population have long- and short-term effects on a place’s 
economy, culture, and politics. 
Source: AP® Human Geography Course and Exam Description. Effective Fall 2020. (College Board).
Page 2


UNIT 2: POPULATION AND MIGRATION PATTERNS AND PROCESSES 53
UNIT 2
Population and Migration 
Patterns and Processes
Chapter 3 Population Distribution and Composition 
Chapter 4 Population Change
Chapter 5 Migration
Unit Overview
The distribution of people influences all other elements of human geography. 
Where people live, whether spread out in small communities or concentrated 
in large cities, affects how they relate to one another, what demands they place 
on the environment, and what decisions they make as a community. 
People decide where to live based on many factors. Some are physical: 
people want to be near sources of food and water and where the climate is not 
too extreme. Some factors are human: people might move to take a job or to 
be close to family.
Changes in Populations
For most of human history, women typically gave birth to many children, but 
so few children survived to adulthood that the total human population grew 
slowly. However, in the past two centuries, advances in public health, medical 
care, and the economy have enabled people to live longer. As a result of these 
new patterns, the global population has exploded. However, in recent decades, 
population growth has leveled off in many wealthy countries, such as Germany, 
South Korea, the United States.
Why People Move
People have always been on the move. Usually, they migrated by choice, wanting 
to leave a place of poverty or persecution or warfare in order to live in a place 
with economic opportunity, religious liberty, political freedom, and peace. 
In some cases, people had no choice. For example, for nearly four centuries, 
Africans were enslaved and brought to the Americas.
ENDURING UNDERSTANDINGS
PSO-2:  Understanding where and how people live is essential to understanding 
global cultural, political, and economic patterns. 
IMP-2:  Changes in population are due to mortality, fertility, and migration, which are 
influenced by the interplay of environmental, economic, cultural, and political 
factors. 
SPS-2:  Changes in population have long- and short-term effects on a place’s 
economy, culture, and politics. 
Source: AP® Human Geography Course and Exam Description. Effective Fall 2020. (College Board).
54 CHAPTER 3: POPULATION DISTRIBUTION AND COMPOSITION
Population Distribution 
and Composition
Topics 2.1–2.3
Topic 2.1 Population Distribution
Learning Objectives: Identify the factors that influence the distribution of human 
populations at different scales. (PSO-2.A)
Define methods geographers use to calculate population density. (PSO-2.B)
Explain the differences between and the impact of methods used to calculate 
population density. (PSO-2.C)
Topic 2.2 Consequences of Population Distribution
Learning Objective: Explain how population distribution and density affect 
 society and the environment. (PSO-2.D)
Topic 2.3 Population Composition
Learning Objectives: Describe elements of population composition used by 
geographers. (PSO-2.E)
Explain ways that geographers depict and analyze population composition. 
(PSO-2.F)
Half the world’s population lives in just 1 percent of the land.
—Max Galka, Metrocosm, January 4, 2016
Source: Getty Images
The image shows city traffic in India. Rapid population growth and density impacts society and 
the environment. (See Topic 2.2 for the effects of population growth.)
CHAPTER 3
Page 3


UNIT 2: POPULATION AND MIGRATION PATTERNS AND PROCESSES 53
UNIT 2
Population and Migration 
Patterns and Processes
Chapter 3 Population Distribution and Composition 
Chapter 4 Population Change
Chapter 5 Migration
Unit Overview
The distribution of people influences all other elements of human geography. 
Where people live, whether spread out in small communities or concentrated 
in large cities, affects how they relate to one another, what demands they place 
on the environment, and what decisions they make as a community. 
People decide where to live based on many factors. Some are physical: 
people want to be near sources of food and water and where the climate is not 
too extreme. Some factors are human: people might move to take a job or to 
be close to family.
Changes in Populations
For most of human history, women typically gave birth to many children, but 
so few children survived to adulthood that the total human population grew 
slowly. However, in the past two centuries, advances in public health, medical 
care, and the economy have enabled people to live longer. As a result of these 
new patterns, the global population has exploded. However, in recent decades, 
population growth has leveled off in many wealthy countries, such as Germany, 
South Korea, the United States.
Why People Move
People have always been on the move. Usually, they migrated by choice, wanting 
to leave a place of poverty or persecution or warfare in order to live in a place 
with economic opportunity, religious liberty, political freedom, and peace. 
In some cases, people had no choice. For example, for nearly four centuries, 
Africans were enslaved and brought to the Americas.
ENDURING UNDERSTANDINGS
PSO-2:  Understanding where and how people live is essential to understanding 
global cultural, political, and economic patterns. 
IMP-2:  Changes in population are due to mortality, fertility, and migration, which are 
influenced by the interplay of environmental, economic, cultural, and political 
factors. 
SPS-2:  Changes in population have long- and short-term effects on a place’s 
economy, culture, and politics. 
Source: AP® Human Geography Course and Exam Description. Effective Fall 2020. (College Board).
54 CHAPTER 3: POPULATION DISTRIBUTION AND COMPOSITION
Population Distribution 
and Composition
Topics 2.1–2.3
Topic 2.1 Population Distribution
Learning Objectives: Identify the factors that influence the distribution of human 
populations at different scales. (PSO-2.A)
Define methods geographers use to calculate population density. (PSO-2.B)
Explain the differences between and the impact of methods used to calculate 
population density. (PSO-2.C)
Topic 2.2 Consequences of Population Distribution
Learning Objective: Explain how population distribution and density affect 
 society and the environment. (PSO-2.D)
Topic 2.3 Population Composition
Learning Objectives: Describe elements of population composition used by 
geographers. (PSO-2.E)
Explain ways that geographers depict and analyze population composition. 
(PSO-2.F)
Half the world’s population lives in just 1 percent of the land.
—Max Galka, Metrocosm, January 4, 2016
Source: Getty Images
The image shows city traffic in India. Rapid population growth and density impacts society and 
the environment. (See Topic 2.2 for the effects of population growth.)
CHAPTER 3
2.1: POPULATION DISTRIBUTION 55
2.1
Population Distribution
Essential Question: What are the factors that influence population 
distribution and what are the impacts of different methods used to 
calculate population density?
Humans live on a small percentage of the planet. The world contains seven 
times as many people today as it did two centuries ago. Population density 
has increased significantly. However, population distribution has not. The 
vast majority of growth has been in areas already settled. For example, eastern 
China was one of the most populated parts of the world in 1800—and it still is 
today. Why have people chosen to live in such crowded places?
Where People Live
People want to live in places where they can survive with relative ease and 
comfort—places where they can raise or obtain food and live in moderate 
climates. Around 1800, when the population was only one billion, people 
were dispersed throughout such desirable lands. As population increased, 
the amount of suitable land stayed about the same, so people chose to live in 
greater densities on that same land.
Human geography tries to explain why people live where they do. It 
includes the study of two distinct but related concepts:
• Population distribution is the pattern of human settlement—the spread 
of people across the earth. Representing it on a map highlights places that 
are crowded, sparsely settled, or even empty.
• Population density is a measure of the average population per square 
mile or kilometer of an area. It measures how crowded a place is.
Understanding both population distribution and density helps people 
make important decisions on issues such as where to set the boundaries of 
an electoral district or where to develop new housing. These are among the 
many issues influenced by the number, distribution, and density of current and 
projected populations.
Physical Factors Influencing Population Distribution
Survival for the earliest humans depended on food, water, and shelter. Thus, 
these hunter-gatherers settled where these features were most readily available. 
Similarly, people today have the same basic needs, which helps explain why the 
population distribution has remained so similar over time. The map of Earth’s 
population distribution today below shows where the highest densities and 
largest numbers of people live today.
Page 4


UNIT 2: POPULATION AND MIGRATION PATTERNS AND PROCESSES 53
UNIT 2
Population and Migration 
Patterns and Processes
Chapter 3 Population Distribution and Composition 
Chapter 4 Population Change
Chapter 5 Migration
Unit Overview
The distribution of people influences all other elements of human geography. 
Where people live, whether spread out in small communities or concentrated 
in large cities, affects how they relate to one another, what demands they place 
on the environment, and what decisions they make as a community. 
People decide where to live based on many factors. Some are physical: 
people want to be near sources of food and water and where the climate is not 
too extreme. Some factors are human: people might move to take a job or to 
be close to family.
Changes in Populations
For most of human history, women typically gave birth to many children, but 
so few children survived to adulthood that the total human population grew 
slowly. However, in the past two centuries, advances in public health, medical 
care, and the economy have enabled people to live longer. As a result of these 
new patterns, the global population has exploded. However, in recent decades, 
population growth has leveled off in many wealthy countries, such as Germany, 
South Korea, the United States.
Why People Move
People have always been on the move. Usually, they migrated by choice, wanting 
to leave a place of poverty or persecution or warfare in order to live in a place 
with economic opportunity, religious liberty, political freedom, and peace. 
In some cases, people had no choice. For example, for nearly four centuries, 
Africans were enslaved and brought to the Americas.
ENDURING UNDERSTANDINGS
PSO-2:  Understanding where and how people live is essential to understanding 
global cultural, political, and economic patterns. 
IMP-2:  Changes in population are due to mortality, fertility, and migration, which are 
influenced by the interplay of environmental, economic, cultural, and political 
factors. 
SPS-2:  Changes in population have long- and short-term effects on a place’s 
economy, culture, and politics. 
Source: AP® Human Geography Course and Exam Description. Effective Fall 2020. (College Board).
54 CHAPTER 3: POPULATION DISTRIBUTION AND COMPOSITION
Population Distribution 
and Composition
Topics 2.1–2.3
Topic 2.1 Population Distribution
Learning Objectives: Identify the factors that influence the distribution of human 
populations at different scales. (PSO-2.A)
Define methods geographers use to calculate population density. (PSO-2.B)
Explain the differences between and the impact of methods used to calculate 
population density. (PSO-2.C)
Topic 2.2 Consequences of Population Distribution
Learning Objective: Explain how population distribution and density affect 
 society and the environment. (PSO-2.D)
Topic 2.3 Population Composition
Learning Objectives: Describe elements of population composition used by 
geographers. (PSO-2.E)
Explain ways that geographers depict and analyze population composition. 
(PSO-2.F)
Half the world’s population lives in just 1 percent of the land.
—Max Galka, Metrocosm, January 4, 2016
Source: Getty Images
The image shows city traffic in India. Rapid population growth and density impacts society and 
the environment. (See Topic 2.2 for the effects of population growth.)
CHAPTER 3
2.1: POPULATION DISTRIBUTION 55
2.1
Population Distribution
Essential Question: What are the factors that influence population 
distribution and what are the impacts of different methods used to 
calculate population density?
Humans live on a small percentage of the planet. The world contains seven 
times as many people today as it did two centuries ago. Population density 
has increased significantly. However, population distribution has not. The 
vast majority of growth has been in areas already settled. For example, eastern 
China was one of the most populated parts of the world in 1800—and it still is 
today. Why have people chosen to live in such crowded places?
Where People Live
People want to live in places where they can survive with relative ease and 
comfort—places where they can raise or obtain food and live in moderate 
climates. Around 1800, when the population was only one billion, people 
were dispersed throughout such desirable lands. As population increased, 
the amount of suitable land stayed about the same, so people chose to live in 
greater densities on that same land.
Human geography tries to explain why people live where they do. It 
includes the study of two distinct but related concepts:
• Population distribution is the pattern of human settlement—the spread 
of people across the earth. Representing it on a map highlights places that 
are crowded, sparsely settled, or even empty.
• Population density is a measure of the average population per square 
mile or kilometer of an area. It measures how crowded a place is.
Understanding both population distribution and density helps people 
make important decisions on issues such as where to set the boundaries of 
an electoral district or where to develop new housing. These are among the 
many issues influenced by the number, distribution, and density of current and 
projected populations.
Physical Factors Influencing Population Distribution
Survival for the earliest humans depended on food, water, and shelter. Thus, 
these hunter-gatherers settled where these features were most readily available. 
Similarly, people today have the same basic needs, which helps explain why the 
population distribution has remained so similar over time. The map of Earth’s 
population distribution today below shows where the highest densities and 
largest numbers of people live today.
56 HUMAN GEOGRAPHY: AP
®
 EDITION
Midlatitudes Most people live in the midlatitudes, the regions between 
30 degrees and 60 degrees, north and south of the equator. These areas have 
more moderate climates and better soils than do regions at higher or lower 
latitudes. This pattern is particularly noticeable in the northern hemisphere 
because it includes more land than the southern hemisphere.
Low-Lying Areas Most people live in low-lying areas rather than high-
alititude areas, such as mountains. Low-lying areas typically have better soils 
for raising crops than do upland or high-altitude areas. In addition, these areas 
are often close to oceans, which facilitate transportation, provide a source 
of food, and have a moderating effect on temperature. Oceans keep the land 
warmer in the winter and cooler in the summer.
Other Factors Most people live near lakes or rivers. People need fresh 
water to drink, and they can use it for irrigation, transportation, and to provide 
food. Regions of the world where it is difficult for humans to live typically 
have low population numbers and densities. These include mountainous 
areas, deserts, and high latitude/cold climates where agriculture is challenging. 
Lower population densities are also found in the tropics where disease is 
more prevalent and poor soils make farming difficult. Polar regions have no 
permanent human populations. 
WORLD POPULATION DISTRIBUTION
< 0.5 – 10
10 – 200
200– 800
800– 2,000
2,000 – 8,000
8,000 – 50,000 <
Source: Wikimedia Commons
Human Factors Influencing Population Distribution
The places humans first settled included natural features that attracted them. 
However, then people themselves became an attraction. Newcomers moved in 
for safety, to find a job, or to be with friends or relatives. The populations and 
densities of cities have continued to grow, often to extreme levels.
Where people place transportation networks also has a significant impact 
on population distribution. People prefer to live close to trade routes. Roads, 
train lines, and rivers often produce a linear settlement pattern in which houses 
and communities stretch out in a line.
Page 5


UNIT 2: POPULATION AND MIGRATION PATTERNS AND PROCESSES 53
UNIT 2
Population and Migration 
Patterns and Processes
Chapter 3 Population Distribution and Composition 
Chapter 4 Population Change
Chapter 5 Migration
Unit Overview
The distribution of people influences all other elements of human geography. 
Where people live, whether spread out in small communities or concentrated 
in large cities, affects how they relate to one another, what demands they place 
on the environment, and what decisions they make as a community. 
People decide where to live based on many factors. Some are physical: 
people want to be near sources of food and water and where the climate is not 
too extreme. Some factors are human: people might move to take a job or to 
be close to family.
Changes in Populations
For most of human history, women typically gave birth to many children, but 
so few children survived to adulthood that the total human population grew 
slowly. However, in the past two centuries, advances in public health, medical 
care, and the economy have enabled people to live longer. As a result of these 
new patterns, the global population has exploded. However, in recent decades, 
population growth has leveled off in many wealthy countries, such as Germany, 
South Korea, the United States.
Why People Move
People have always been on the move. Usually, they migrated by choice, wanting 
to leave a place of poverty or persecution or warfare in order to live in a place 
with economic opportunity, religious liberty, political freedom, and peace. 
In some cases, people had no choice. For example, for nearly four centuries, 
Africans were enslaved and brought to the Americas.
ENDURING UNDERSTANDINGS
PSO-2:  Understanding where and how people live is essential to understanding 
global cultural, political, and economic patterns. 
IMP-2:  Changes in population are due to mortality, fertility, and migration, which are 
influenced by the interplay of environmental, economic, cultural, and political 
factors. 
SPS-2:  Changes in population have long- and short-term effects on a place’s 
economy, culture, and politics. 
Source: AP® Human Geography Course and Exam Description. Effective Fall 2020. (College Board).
54 CHAPTER 3: POPULATION DISTRIBUTION AND COMPOSITION
Population Distribution 
and Composition
Topics 2.1–2.3
Topic 2.1 Population Distribution
Learning Objectives: Identify the factors that influence the distribution of human 
populations at different scales. (PSO-2.A)
Define methods geographers use to calculate population density. (PSO-2.B)
Explain the differences between and the impact of methods used to calculate 
population density. (PSO-2.C)
Topic 2.2 Consequences of Population Distribution
Learning Objective: Explain how population distribution and density affect 
 society and the environment. (PSO-2.D)
Topic 2.3 Population Composition
Learning Objectives: Describe elements of population composition used by 
geographers. (PSO-2.E)
Explain ways that geographers depict and analyze population composition. 
(PSO-2.F)
Half the world’s population lives in just 1 percent of the land.
—Max Galka, Metrocosm, January 4, 2016
Source: Getty Images
The image shows city traffic in India. Rapid population growth and density impacts society and 
the environment. (See Topic 2.2 for the effects of population growth.)
CHAPTER 3
2.1: POPULATION DISTRIBUTION 55
2.1
Population Distribution
Essential Question: What are the factors that influence population 
distribution and what are the impacts of different methods used to 
calculate population density?
Humans live on a small percentage of the planet. The world contains seven 
times as many people today as it did two centuries ago. Population density 
has increased significantly. However, population distribution has not. The 
vast majority of growth has been in areas already settled. For example, eastern 
China was one of the most populated parts of the world in 1800—and it still is 
today. Why have people chosen to live in such crowded places?
Where People Live
People want to live in places where they can survive with relative ease and 
comfort—places where they can raise or obtain food and live in moderate 
climates. Around 1800, when the population was only one billion, people 
were dispersed throughout such desirable lands. As population increased, 
the amount of suitable land stayed about the same, so people chose to live in 
greater densities on that same land.
Human geography tries to explain why people live where they do. It 
includes the study of two distinct but related concepts:
• Population distribution is the pattern of human settlement—the spread 
of people across the earth. Representing it on a map highlights places that 
are crowded, sparsely settled, or even empty.
• Population density is a measure of the average population per square 
mile or kilometer of an area. It measures how crowded a place is.
Understanding both population distribution and density helps people 
make important decisions on issues such as where to set the boundaries of 
an electoral district or where to develop new housing. These are among the 
many issues influenced by the number, distribution, and density of current and 
projected populations.
Physical Factors Influencing Population Distribution
Survival for the earliest humans depended on food, water, and shelter. Thus, 
these hunter-gatherers settled where these features were most readily available. 
Similarly, people today have the same basic needs, which helps explain why the 
population distribution has remained so similar over time. The map of Earth’s 
population distribution today below shows where the highest densities and 
largest numbers of people live today.
56 HUMAN GEOGRAPHY: AP
®
 EDITION
Midlatitudes Most people live in the midlatitudes, the regions between 
30 degrees and 60 degrees, north and south of the equator. These areas have 
more moderate climates and better soils than do regions at higher or lower 
latitudes. This pattern is particularly noticeable in the northern hemisphere 
because it includes more land than the southern hemisphere.
Low-Lying Areas Most people live in low-lying areas rather than high-
alititude areas, such as mountains. Low-lying areas typically have better soils 
for raising crops than do upland or high-altitude areas. In addition, these areas 
are often close to oceans, which facilitate transportation, provide a source 
of food, and have a moderating effect on temperature. Oceans keep the land 
warmer in the winter and cooler in the summer.
Other Factors Most people live near lakes or rivers. People need fresh 
water to drink, and they can use it for irrigation, transportation, and to provide 
food. Regions of the world where it is difficult for humans to live typically 
have low population numbers and densities. These include mountainous 
areas, deserts, and high latitude/cold climates where agriculture is challenging. 
Lower population densities are also found in the tropics where disease is 
more prevalent and poor soils make farming difficult. Polar regions have no 
permanent human populations. 
WORLD POPULATION DISTRIBUTION
< 0.5 – 10
10 – 200
200– 800
800– 2,000
2,000 – 8,000
8,000 – 50,000 <
Source: Wikimedia Commons
Human Factors Influencing Population Distribution
The places humans first settled included natural features that attracted them. 
However, then people themselves became an attraction. Newcomers moved in 
for safety, to find a job, or to be with friends or relatives. The populations and 
densities of cities have continued to grow, often to extreme levels.
Where people place transportation networks also has a significant impact 
on population distribution. People prefer to live close to trade routes. Roads, 
train lines, and rivers often produce a linear settlement pattern in which houses 
and communities stretch out in a line.
57 2.1: POPULATION DISTRIBUTION
Political decisions sometimes bring clusters of populations to isolated 
locations where physical attributes would not normally attract settlement. For 
example, in 1950, Canada wanted a military base that could monitor possibly 
hostile actions by the country then known as the Soviet Union. So, it established 
a military base named Alert on the northern edge of its territory, in a land 
of ice, snow, and bitterly cold temperatures. Alert remains the most northerly 
community in the world.
Scale of Analysis and Physical Factors
The basic principle that people want to live on the most desirable land applies 
at any scale, or level of analysis by size. (See Topic 1.6 for more on scales of 
analysis.) As the scale of analysis changes, the relevance of certain factors such 
as climate, elevation, and industrialization changes as well.
At the global scale, regions with very high elevations—mountainous 
regions such as in the Himalayas, the Andes, and the Rocky Mountains—
have cold climates, so such places usually have limited populations. However, 
elevation is sometimes important at the city level. People might prefer living 
at the highest elevations in a city because these spots offer cool breezes, safety 
from floods, and inspiring views of the landscape. At a regional scale, climate 
can also explain population distribution of a state such as California, where 
climate varies greatly within the state. For example, coastal California has a 
very large population compared to the desert and mountain regions of the 
interior. On a larger or local scale, such as a city, the spatial climate variation is 
usually too small to affect settlement. 
Scale of Analysis and Human Factors
Polluted air is a health hazard, yet it may signal industrialization, economic 
development, and employment opportunities. On a global or national scale, 
millions of people are attracted to cities in search of economic opportunities 
and they might knowingly move to a polluted area. At a local scale, few people 
intentionally choose to settle near a pollution source unless they have to live 
there because lower property values make it more affordable.
Governments also have a significant influence on population distribution 
at different scales. A national government might increase the population of an 
area by building a new military base. A state might reduce population in an 
area by creating a new state park. A city government might affect population 
distribution by allowing high-rise apartment buildings in some areas and 
reserving other areas for single-family homes. (See Topic 6.6.)
Factors influencing a city’s population distribution such as elevation, 
proximity to desirable land, and land use laws commonly result in a population 
distribution that reflects social stratification —the hierarchical division of 
people into groups based on factors such as economic status, power, and/
or ethnicity. Cities are characterized by regions and neighborhoods where 
the local population shares a characteristic that distinguishes it from other 
neighborhoods. For example, a neighborhood with large homes and parks