1. Population Dynamics
J vs. S shaped growth

2. Principles of Population Growth
What is a population?
A healthy or stable population will grow and die at a steady rate unless it runs out of food or space, or is attacked in some way by disease or predators. (it encounters a limiting factor of some type)

3. Scientists study growth in a variety of ways
One way involves introducing an organism into a sterile, nutrient rich environment.
This is going to be for smaller organisms such as bacteria
Another way is through field studies and radio tagging organisms
Larger organisms such as elk

4. Populations do not follow linear growth increase.
Instead they start out slowly but once they build up the rate increases dramatically
Population Growth of Houseflies
1 million
500,000
Population size
100
One year

5. This type of growth is called exponential growth.
Exponential growth means that as a population size increases the rate of growth also increases.
Exponential growth results in a J-shaped graph curve.

6. If left unchecked exponential growth would continue forever.
In reality we know that it doesn’t. At some point growth stops.
This is where limiting factors come into play.
They are going to prevent the population from exceeding an imaginary line called a carrying capacity.
A carrying capacity is the number of organisms that an environment can support indefinitely, without outside assistance.

7. When looking at a graph illustrating population growth with a carrying capacity the j-shaped curve becomes an s-shaped curve
Characteristics of Population Growth
Exponential growth
PREDA-TORS
DISEASE
SPACE
FOOD
Carrying capacity
J curve
S curve
Population
Time

8. Most species follow a set path of population growth
They start of with slow growth
Then there is a period of rapid growth as it enters exponential growth
Next it reaches its carrying capacity and levels off
However there are still some fluctuations in the numbers