1. Populations
- Chapter 19

2. Characteristics of Populations
Three important characteristics of a population are:
Geographic Distribution
Density
Growth Rate
Also:
Age Structure of the Population

3. Three factors can affect population size:
Population Dynamics
Three factors can affect population size:
Number of Births
Number of Deaths
Life expectancy
Age structure

4. Population Growth Rate
Definition: the amount by which a population‘s size changes in a given time.
Birth rate – death rate = growth rate.

5. Immigration
– the movement of individuals into an area/population
Emigration
- the movement of individuals out of an area/population

6. Exponential Growth
Under ideal conditions, a population will continue to grow in a pattern called exponential growth.
Exponential Growth occurs when individuals in a population reproduce at a constant rate.

7. Exponential Growth

8. Logistic Growth
As resources become less available, the growth of a population slows or stops.
Logistic Growth occurs when a population’s growth slows or stops following a period of exponential growth.

9. Carrying Capacity
The point at which the average growth rate reaches zero.
It is the largest number of individuals that a given environment can support

10. Logistic Growth and Carrying Capacity

11. Limits to Growth Limiting Factors
Factors that cause population growth to decrease

12. Density-Dependent Limiting Factors
A limiting factor that depends on population size
Includes:
Competition
Predation
Parasitism
Disease

13. Parasitism
Climate
Competition
Predation
Human Disturbances

14. Density-Dependent Limiting Factors

15. Density-Independent Limiting Factors
Affect all populations in similar ways, regardless of the population size.
Includes:
Unusual Weather
Natural Disaster
Seasonal Cycles
Human Activities

16. Human Population Growth
The size of the human population tends to increase with time.
The scientific study of human populations is called demographics.

17. Human Population Growth

18. These factors can be shown in an age-structure diagram.
Some factors that help predict why some countries have high growth rates while other countries grow more slowly are:
Birthrates
Death rates
Age Structure
These factors can be shown in an age-structure diagram.

19. Age Structure Diagrams