2. This presentation is available online at www.redwood.org/stewart

3. I. Population Growth Patterns 1. What is a population?

4. 2. Resources determine how a given population will grow.

5. Exponential Growth (using algebra):

6. Exponential Growth (without using algebra): “doubling time”

7. Exponential Growth (without using algebra): The effect of “doubling time” The Emperor’s Reward to the Inventor of Chess: “…give me one grain of wheat for the first square, two for the second and so on, doubling the grains for each of the 64 squares of the chess board.”

8. a. EXPONENTIAL GROWTH happens when there are UNLIMITED RESOURCES available to the population (usually early in the population’s growth). Populations grow when: birth rate + immigration > death rate + emigration (# of organisms moving in) (# of organisms moving out) Can exponential growth go on forever? No.

9. 3. Exponential growth is part of a more complete picture of population growth known as “LOGISTIC GROWTH”. Logistic growth curves demonstrate the natural (logical) progression/phases of population growth from slow, to moderate, to fast, to level or collapse. EVENTUALLY THE GROWTH WILL LEVEL OFF OR COLLAPSE. THIS ENTIRE PROGRESSION IS KNOWN AS LOGISTIC GROWTH. A STEADY STATE GROWTH LEVELING OFF C,D E B or COLLAPSE?

10. 4. Over time, in real environments, exponential growth can not be sustained (not enough resources). So… The population growth may level off. This is known as reaching a “STEADY STATE”. This is also sometimes referred to as an “S- Curve”.

11. 4. Over time, in real environments, exponential growth can not be sustained (not enough resources). So… The other possibility is that the population will COLLAPSE. This is also sometimes referred to as a “J-Curve”.

12. 5. Reaching steady state or collapse is part of population logistics because resources are finite. The theoretical point beyond which a population can no longer be sustained is known as the CARRYING CAPACITY (K). Result: Steady state or… Collapse

14. II. Limiting Factors 1. Resources, nutrients (matter) and energy in short supply, limit how large a population can grow, therefore resources can be limiting factors.

15. 2.Density-dependent limiting factors control population size when a population is large and crowded. a. EXAMPLES : competition, predation, parasitism and crowding 3.Density-independent limiting factors control population size regardless of whether a population is large or small. a.EXAMPLES:natural causes such as geothermal activity, extreme weather (Steady state/ S-curve) Or not…

16. Sometimes populations grow beyond the “control” of limiting factors… (Collapse/ J-curve) THE END!?