1. Populations & Ecological Succession
Chapters 4 & 5

2. What is a population?
A group of organisms of the same species that live in the same area.

3. 3 Major Characteristics of Populations
1) Geographic distribution
2) Density
3) Growth Rate

4. Geographic Distribution AKA “range”
Where the population is located.

5. Density How closely the individuals live to one another.
The lower the density, the more personal space each individual has.

6. Growth Rate How quickly the size of the population is changing. Can be
getting
bigger or
smaller

7. What causes changes in population size?
Increase in size
Births
Immigration
(In-migration)
Decrease in size
Death
Emigration
(Exit – migration)

8. Common Growth Patterns
There are two very common patterns of growth.
Exponential
Logistic

9. Exponential Growth “J-shaped” growth
Growth starts out slowly, then skyrockets.
Occurs only in “perfect” conditions:
No disease
No predators
Unlimited space
Unlimited food
and water

10. Logistic Growth “S-shaped” growth
Starts out like exponential growth, but eventually levels out.
Growth pattern
of most real
populations.

11. Carrying capacity (K)
The maximum number of individuals of a particular species that the environment can support.
Determines the point at
which a population stops
growing.

12. Limiting Factors Anything that causes a population to stop growing.
Can be:
a shortage of food,
water, nutrients or shelter.

13. Density-Dependent Factors
Things that only slow/stop population growth when there is a high density.
This is because you now have many organisms living close to one another.
Disease
Predation
Parasites
Competition (food, water, shelter, mates, etc.)

14. Density-Independent Factors
Things that slow any population’s growth, regardless of density.
Natural disasters (tornados, hurricanes, earthquakes, etc.)
Seasonal changes (winter freeze)
Human activity (Pollution, deforestation, global warming, etc.)