1. Chapter 19 Table of Contents Section 1 Understanding Populations
Section 2 Measuring Populations
Section 3 Human Population Growth

2. Section 1 Understanding Populations
Chapter 19
Objectives
Describe the main properties that scientists measure when they study populations.
Compare the three general patterns of population dispersion.
Identify the measurements used to describe changing populations.
Compare the three general types of survivorship curves.

3. Properties of Populations
Section 1 Understanding Populations
Chapter 19
Properties of Populations
A population is a group of organisms that belong to the same species and live in a particular place at the same time.
Populations can be measured in terms of size, density, dispersion, growth rate, age structure, and survivorship.

4. Chapter 19 Population Section 1 Understanding Populations
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Visual Concept

5. Properties of Populations, continued
Section 1 Understanding Populations
Chapter 19
Properties of Populations, continued
Population Size
A population’s size is the number of individuals that the population contains.

6. Properties of Populations, continued
Section 1 Understanding Populations
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Properties of Populations, continued
Population Density
Density is a measure of how crowded the population is.

7. Properties of Populations, continued
Section 1 Understanding Populations
Chapter 19
Properties of Populations, continued
Dispersion
Dispersion describes the distribution of individuals within the population and may be random, uniform, or clumped.

8. Three Patterns of Population Dispersion
Section 1 Understanding Populations
Chapter 19
Three Patterns of Population Dispersion

9. Characteristics of Populations
Section 1 Understanding Populations
Chapter 19
Characteristics of Populations
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Visual Concept

10. Chapter 19 Population Dynamics Age Structure
Section 1 Understanding Populations
Chapter 19
Population Dynamics
Age Structure
A population’s age structure indicates the percentage of individuals at each age.

11. Population Dynamics, continued
Section 1 Understanding Populations
Chapter 19
Population Dynamics, continued
Patterns of Mortality
Populations show three patterns of mortality or survivorship curves:
Type I (low mortality until late in life)
Type II (constant mortality throughout life)
Type III (high mortality early in life followed by low mortality for the remaining life span).

12. Section 1 Understanding Populations
Chapter 19
Survivorship Curves

13. Section 2 Measuring Populations
Chapter 19
Objectives
Identify the four processes that determine population growth.
Compare the exponential model and the logistic model of population growth.
Differentiate between density-dependent and density-independent regulation of populations.
Explain why small populations are more vulnerable to extinction.

14. Population Growth Rate
Section 2 Measuring Populations
Chapter 19
Population Growth Rate
Demographers, scientists who study population dynamics, define the growth rate of a population as the amount by which a population’s size changes in a given time.

15. Population Growth Rate, continued
Section 2 Measuring Populations
Chapter 19
Population Growth Rate, continued
Population Size
Birth rate - death rate = growth rate

16. Chapter 19 The Exponential Model
Section 2 Measuring Populations
Chapter 19
The Exponential Model
The exponential model describes perpetual growth at a steady rate in a population.
The model assumes constant birth and death rates and no immigration or emigration.

17. Chapter 19 Exponential Growth Section 2 Measuring Populations
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Visual Concept

18. Chapter 19 The Logistic Model
Section 2 Measuring Populations
Chapter 19
The Logistic Model
In the logistic model, birth rates fall and death rates climb as the population grows.
When the carrying capacity is reached, the number of individuals the environment can support is reached and population growth becomes stable.

19. Chapter 19 Logistic Model Section 2 Measuring Populations
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Visual Concept

20. Two Population Growth Models
Section 2 Measuring Populations
Chapter 19
Two Population Growth Models

21. Population Regulation
Section 2 Measuring Populations
Chapter 19
Population Regulation
Population-limiting factors, such as competition, are density-dependent because the effect on each individual depends on the number of other individuals present in the same area.

22. Population Regulation, continued
Section 2 Measuring Populations
Chapter 19
Population Regulation, continued
Population-limiting factors, such as bad weather and fires, are density-independent because the effect on each individual does not depend on the number of other individuals present in the same area.

23. Comparing Density-Dependent and Density-Independent Factors
Section 2 Measuring Populations
Chapter 19
Comparing Density-Dependent and Density-Independent Factors
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Visual Concept

24. Population Regulation, continued
Section 2 Measuring Populations
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Population Regulation, continued
Population Fluctuations
All populations fluctuate in size.

25. Population Regulation, continued
Section 2 Measuring Populations
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Population Regulation, continued
Perils of Small Populations
Small populations have low genetic diversity and are subject to inbreeding, so they are less likely to adapt to environmental changes.

26. Section 3 Human Population Growth
Chapter 19
Objectives
Explain how the development of agriculture changed the pattern of human population growth.
Describe changes in human population size in the past 10,000 years.
Compare observed patterns of population growth in developed and developing countries.

27. History of Human Population Growth
Section 3 Human Population Growth
Chapter 19
History of Human Population Growth
The Development of Agriculture
About 10,000 to 12,000 years ago, the development of agriculture increased the growth rate of the human population.

28. History of Human Population Growth, continued
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History of Human Population Growth, continued
The Population Explosion
Around 1650, improvements in hygiene, diet, and economic conditions further accelerated population growth.
After World War II, the human population grew at the fastest rate in history, largely because of better sanitation and medical care in poorer countries.

29. History of Human Population Growth, continued
Section 3 Human Population Growth
Chapter 19
History of Human Population Growth, continued
Population Growth Today
Today, developing countries have faster human population growth and lower standards of living than developed countries do.

30. Human Population Growth
Section 3 Human Population Growth
Chapter 19
Human Population Growth

31. Demographic Transition
Section 3 Human Population Growth
Chapter 19
Demographic Transition
Human populations have undergone rapid growth, yet in some developed countries, populations have stopped growing.
The demographic transition model shows how these population changes happen.

32. Demographic Transition Model
Section 3 Human Population Growth
Chapter 19
Demographic Transition Model