Population Dynamics

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

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

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”.

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.

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.)

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

By Anne Morgan, Biology Teacher and Homeschool Co-op Educator Images from mycutegraphics.com If you like this Powerpoint, please rate it at the TeachersPayTeachers Product page. I get valuable feedback and you get TpT credits towards future purchases! It’s a win-win!