1. Population Dynamics

2. How fast do populations grow?
Would you rather be paid $5.00/hr for a 20 hour week, or a salary that starts at 1¢ the first hour and doubles each hour up to 20 hours?
Do the math!
5.00 x 20 = $100.00
1¢ doubling every hour = $10485

3. If we graphed these salaries, this is what they would look like:

4. Populations of organisms increase exponentially.
Exponential growth occurs when the number of organisms rises at an ever-increasing rate.
We call this graph a “J curve”.

5. Why don’t the populations increase indefinitely?
The environment limits populations from increasing forever.
What are these “limits” called?
LIMITING FACTORS!
The number of organisms that an environment can support over a long period of time is called the carrying capacity.

6. There are 2 types of limits that regulate the size of a population:
Density-dependent factors = have an increasing effect as the population increases.
Example: predators, disease, competition, etc.
(Hint: usually these are biotic.)
Density-independent factors = affect all populations, regardless of how large.
Example: temperature, storms, floods, drought, etc.
(Hint: usually these are abiotic.)

7. Logistic Model of Growth
When the limiting factors LIMIT the population, the J curve will not continue to increase
It levels off at the carrying capacity
This is called an S curve

8. By Anne Morgan, Biology Teacher and Homeschool Co-op Educator
Images from mycutegraphics.com
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