1. Population Growth
How Populations Grow

2. Populations Growth Population Growth
Three factors can affect population size:
number of births (Birth Rate)
the number of deaths (Death Rate)
the number of individuals that enter or leave the population.
* Simply put, a population will increase or decrease in size depending on how many individuals are added to it or removed from it

3. Immigration & Emmigration
the movement of individuals into an area, is another factor that can cause a population to grow.
Emigration
the movement of individuals out of an area, can cause a population to decrease in size.

4. The rise and fall of populations…..
Populations Increase:
A higher birthrate in comparison to death rate
Immigration
Populations Decrease:
A higher death rate in comparison to birth rate
Emigration

5. What if……
A population is provided with food, space, shelter, protection from predators and disease?
The population will grow……because?

6. Exponetial Growth Exponential Growth (J-shaped curve)
If a population has abundant space and food, and is protected from predators and disease, then organisms in that population will multiply and the population size will increase.
**unlimited resources

8. Exponential Growth Exponential growth occurs when:
the individuals in a population reproduce slowly
Example: bacteria
A change in a new environment (for a time)
Example: invasive speciese
Organisms reproduce slowly
Example: Elephants produce offspring 2-4 years

9. Checkpoint
Which of the following is NOT a condition for a population to reach exponential growth?
A.) presence of unlimited resources
B.) Absence of predation and disease
C.) movement of individuals out of the population

10. Logistic Growth
Logistic growth occurs when a population's growth slows or stops following a period of exponential growth; levels off at Carrying Capacity
As resources become less available, the growth of a population slows or stops. The general, S-shaped curve of this growth pattern, called logistic growth

11. Carrying Capacity Carrying Capacity
The number or the largest number of individuals that a given environment can support.

13. Phases of a Logistic Growth:
I: Exponential Growth: unlimited resources
II: Growth Slows Down: Population still grows, BUT rate of the growth is slowing down
III: Growth stops: Population is its carrying capacity

14. Closure Question: What shape population growth curve would you expect to see in a small town made up of Senior citizens? Why? What shape population growth curve would you expect to see in a small town made up of newly married couples in their twenties? Why?

15. Using Graphic Organizers
Draw a concept map that shows how populations grow. Include the following terms: exponential growth, logistic growth, birthrate, death rate, immigration, emigration. Add any other terms that you think are useful to complete the map

16. Population Density
Population density is the number of individuals per unit area.
The population of saguaro cactus in the desert plant community has a low density, whereas other plants in that community have a relatively high density.

17. What factors determine carrying capacity?
Limiting Factors!
A factor that controls the growth of a population
Examples:
Competition
Predation
Disease
Unusual Weather
Disasters
Limited nutrients (productivity)

18. Limiting Factors determine the CARRYING CAPACITY of an environment for a species!!!!

19. Density-Dependent Factors
Limiting factor is DEPENDENT on the population density
Competition
Predation
Herbivory
Disease
Stress from overcrowding

20. Real Life Examples
Competition
Predator/Prey

21. Density-Independent Factors
Limiting Factors that affect ALL populations in similar ways, REGARDLESS of population size and density
Hurricanes
Droughts
Floods
Natural disasters (wildfires)

22. Real life examples
Drought
Hurricane Sandy

23. Now……..
YOU COME UP WITH REAL LIFE EXAMPLES OF DENSITY-DEPENDENT AND DENSITY-INDEPENDENT FACTORS