Transcript Ch 5 Populations

1 Review Describe the general trends of human
population growth over time
2 Review why do populations in different countries
grow at different rates
Form an Opinion Are age structures diagrams useful
in predicting future population trends
3 Visual Thinking Describe the changes in human
population predicted by the graph on pg 119. How
do you think those changes will affect society.
CH 5 POPULATIONS
5.3 Human Population Growth



How quickly is the global human population
growing
Worldwide, there are more than four human births
every second
What does human population growth mean for us
and our interactions with the rest of the biosphere.
Historical Overview

Population grew very slowly
 Food
shortages
 High predation and diseases
 Harsh life
 Very high birth rate.
Exponential Human Population Growth



Improved nutrition, sanitation, medicine, and
healthcare, dramatically reduced death rates,
industrial revolution
Easier life
Birth rates stayed high.
Thomas Malthus


Thought that human populations would be regulated
by competition (war), limiting resources (famine),
parasitism (disease), and other density-dependent
factors
Thought human growth rate would grow faster than
the increase of food production.


Exponential growth continued up to the second half
of the twentieth century, reaching a peak around
1962–1963, and then it began to drop
Still increasing but at a lower rate.
Patterns of Human Population Growth



Affected by social and economic factors
Birthrates, death rates, and the age structure of a
population play a role
Demography
 Scientific

study of human populations
Demographic transition
 Dramatic
change from high birthrates and death rates
to low birthrates and death rates.
Demographic Transition

Stage 1
 Birthrates
and death rates are high.
Demographic Transition

Stage 2
 Advances
in nutrition, sanitation, and medicine lead to
lower death rates.
Demographic Transition

Stage 3
 Higher
level of education and living standards, families
have fewer children and the birthrate falls.
Age Structure and Population Growth
Future Population Growth

Project 9 BILLION by
2050.