Graph shows Human Population Growth between 10,000 B.C. and 2000 A.D.

FIGURE 5–11 Human Population Growth Over Time After a slow start, the human population grew exponentially following advances in civilization. Change can be dramatic; these photos of Katmandu, Nepal, were taken from the same position in 1969 and 1999—just 30 years apart!

d

Two photographs of Kathmandu, Nepal taken from the same position in the year 1969 and 1999 illustrates the dramatic change in the growth of population over time. In 1969, the place had fields and huts, whereas in 1999 it has buildings and cars.

World Population Growth Slows So what is happening to human population growth today? Exponential growth continued up to the second half of the twentieth century. The human population growth rate reached a peak around 1962–1963, and then it began to drop. The size of the global human population is still growing rapidly, but the rate of growth is slowing down.

It took 123 years for the human population to double from 1 billion in 1804 to 2 billion in 1927. Then it took just 33 years for it to grow by another billion people. The time it took for the population to increase each additional billion continued to fall until 1999, when it began, very slowly, to rise. It now takes longer for the global human population to grow by 1 billion than it did 20 years ago. What has been going on?

Patterns of Human Population Growth

Why do population growth rates differ among countries?

Scientists have identified several social and economic factors that affect human population growth. The scientific study of human populations is called demography. Demography examines characteristics of human populations and attempts to explain how those populations will change over time. Birthrates, death rates, and the age structure of a population help predict why some countries have high growth rates while other countries grow more slowly.

In Your Notebook Explain how the size of the global human population can increase while the rate of growth decreases.

End ofPage 143

Table of Contents

Miller & Levine Biology
About the Authors
Changing the World of Biology Education
Contents
Diversity of Life: A Visual Guide DOL•1–DOL•64
Labs and Activities
Features
UNIT 1 The Nature of Life
1 The Science of Biology
2 The Chemistry of Life
Unit Project
UNIT 2 Ecology
3 The Biosphere
4 Ecosystems and Communities
5 Populations
6 Humans in the Biosphere
Unit Project
UNIT 3 Cells
7 Cell Structure and Function
8 Photosynthesis
9 Cellular Respiration and Fermentation
10 Cell Growth and Division
Unit Project
UNIT 4 Genetics
11 Introduction to Genetics
12 DNA
13 RNA and Protein Synthesis
14 Human Heredity
15 Genetic Engineering
Unit Project
UNIT 5 Evolution
16 Darwin's Theory of Evolution
17 Evolution of Populations
18 Classification
19 History of Life
Unit Project
UNIT 6 From Microorganisms to Plants
20 Viruses and Prokaryotes
21 Protists and Fungi
22 Introduction to Plants
23 Plant Structure and Function
24 Plant Reproduction and Response
Unit Project
UNIT 7 Animals
25 Introduction to Animals
26 Animal Evolution and Diversity
27 Animal Systems I
28 Animal Systems II
29 Animal Behavior
Unit Project
UNIT 8 The Human Body
30 Digestive and Excretory Systems
31 Nervous System
32 Skeletal, Muscular, and Integumentary Systems
33 Circulatory and Respiratory Systems
34 Endocrine and Reproductive Systems
35 Immune System and Disease
Unit Project
A Visual Guide to The Diversity of Life
HOW TO USE THIS GUIDE
THE TREE OF LIFE
Bacteria
Protists
Fungi
Plants
Animals
Appendices
Appendix A Science Skills
Appendix B Lab Skills
Appendix C Technology & Design
Appendix D Math Skills
Appendix E Periodic Table
Glossary
A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q, R
S
T
U
V
W
X, Y, Z
Index
A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q
R
S
T
U
V
W
X
Y
Z
Credits
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