1. Understanding Population Dynamics
Chapter 19
Objectives
Describe how populations are measured and how populations change
Compare the exponential model and the logistic model of population growth.
Explain how change in population density is affected by emigration, immigration, birth rate, and death rate

2. Properties of Populations
Section 1 Understanding Populations
Chapter 19
Properties of Populations
Population- 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 -Growth rate
Density -Age Structure
Dispersion -Survivorship

3. Chapter 19 Population Size
Section 1 Understanding Populations
Chapter 19
Population Size
Population’s size = number of individuals in a population
Population Density
Population Density = how crowded the population is.
High Density Low Density

4. Population Dynamics:How a population can be represented…
Section 1 Understanding Populations
Chapter 19
Population Dynamics:How a population can be represented…
Age Structure
A population’s age structure indicates the percentage of individuals at each age.

5. Population Growth Rate
Section 2 Measuring Populations
Chapter 19
Population Growth Rate
Growth rate of a population is the amount by which a population’s size changes in a given time.
Birth rate - death rate = growth rate
Or find percentage….

6. Section 2 Measuring Populations
Chapter 19
Objectives
Compare the exponential model and the logistic model of population growth.

7. Chapter 19 The Exponential Model
Section 2 Measuring Populations
Chapter 19
The Exponential Model
Exponential model= continual population growth at a steady rate
The model assumes constant birth and death rates and no immigration or emigration.
*Immigration=current individuals leave area
ex.England to U.S.A
*Emigration=new individuals move into area
ex.U.S.A from England

8. Chapter 19 The Logistic Model
Section 2 Measuring Populations
Chapter 19
The Logistic Model
Logistic model= birth rates fall and death rates climb as the population grows because the population reaches its carrying capacity.
Carrying capacity = the number of individuals the environment can support is reached, population growth becomes stable.

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

10. Follow-Up: How do birth rate, death rate, emigration and immigration affect population density? Which model (exponential or logistic) does the human species follow? What do you think causes a population to reach its carrying capacity?