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Chapter 14: Populations Section 14-3: Human Population Growth

Chapter 14: Populations Section 14-3: Human Population Growth

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Page 1: Chapter 14: Populations Section 14-3: Human Population Growth

Chapter 14:Populations

Section 14-3:

Human Population Growth

Page 2: Chapter 14: Populations Section 14-3: Human Population Growth

Growth Increases

For most of human existence, human populations grew slowly because of population-limiting factors like harsh conditions, lack of food, predators, and parasites

Until recently, only half of children lived to adulthood and families had many children to ensure some of them would survive

Page 3: Chapter 14: Populations Section 14-3: Human Population Growth

Quick Growth

Human population began exploding ~300 years ago

Agricultural/industrial revolutions have made human life easier, allowing people to combat population-limiting factors

More nutritious foods are more readily available, doctors can cure, treat, and prevent many diseases, better health care has led to more infants surviving

Page 4: Chapter 14: Populations Section 14-3: Human Population Growth

Quick Growth

All of these factors combined to lower human death rates, and birth rates have either stayed the same or increased

Currently, the human population is now in a state of exponential growth – about 180 people are born every minute, which is about 92 million more humans each year

Page 5: Chapter 14: Populations Section 14-3: Human Population Growth

Population Clocks

http://www.census.gov/main/www/popclock.html

Page 6: Chapter 14: Populations Section 14-3: Human Population Growth

Controlling Human Populations

Human populations would stop growing if birth rates fell, death rates rose, or both

In some countries/parts of the world, population growth has slowed

These populations have gone through the demographic transition, which is a change in growth rate resulting from changes in birth rates

Page 7: Chapter 14: Populations Section 14-3: Human Population Growth

Demographic Transition

Stage 1: There is a high birth rate and a high death rate.

Families have many children to ensure some will survive.

Population growth is slow because birth rate and death rate are both high.

Page 8: Chapter 14: Populations Section 14-3: Human Population Growth

Demographic Transition

Stage 2: Improvements are made in living conditions.

Food production increases, advances are made in medicine and sanitation.

More children live to adulthood and death rate decreases while birth rate remains high, leading to rapid population growth.

Page 9: Chapter 14: Populations Section 14-3: Human Population Growth

Demographic Transition

Stage 3: Birth rate decreases.More children survive, therefore families

have fewer children.Birth rate and death rate reach balance

at a lower level.Population growth slows down and may

stabilize.

Page 10: Chapter 14: Populations Section 14-3: Human Population Growth

World Population Growth

World population continues to grow exponentially because most people live in countries that have not yet completed the demographic transition

The US, Canada, Japan, and most European countries have gone through all three stages

The countries of Asia, Africa, and South America have not yet gone through demographic transition

Page 11: Chapter 14: Populations Section 14-3: Human Population Growth

World Population Growth

Future population growth in various countries depends, in part, on how many people of different ages are living in that country today

Age Structure Diagrams – show the percentage of the population of individuals within a 5-year age group

Page 12: Chapter 14: Populations Section 14-3: Human Population Growth

Age-Structure Diagrams