Population Growth Analyses-2

III) Field Data on Population Growth

1. Seasonal growth when condition favorable not continuous

2. Long-lived organisms may increase populations rarely

3. Few populations fill up space or habitat in nature like lab

4. Example: Reindeer introduced AK

         a. When growth is large chaotic fluctuations

5. Example: Whooping Crane reintroduction

         a. Variable r over time (10-yr cycles)

6. Example: Diatoms other phytoplankton (seasonal max)

7. Conclusion:

         a. Most pop. may not be "density dependent"

         b. Not in a predictable linear manner

8. Current Approaches to Population Modeling

         a. Include time-lag > complex organisms

         b. Develop stochastic models - probabilities

         c. Specific age or size class pop. projection models

9. Stochastic models population growth

         a. Use probabilities to predict change over time

         b. Contrast deterministic models - one outcome

                     where Ro = 2.0 and Nt = 6

                     then Nt+1 = RoNt = 12

         c. Example: More random component - chance events

10. Population Projection Matrices

         a. Age classified life cycle

         b. Stage classified life cycle

         c. Similar to life table @stage refers to age in age classified

         d. Probability age group x to survive into x+1 interval (Px)

         e. They reproduce a number of offspring (Fx)

         f. Age structure: at time t

                     -No = ages between 0-1

                     -Nt = ages between 1-2... to Nk (oldest)

         g. Assuming no immigration or emigration

                     -Population age structure at next time interval:

         h. Matrix algebra solve @ time step

                     i. Birth rates for @ class

                     ii. Probabilities getting to next class

         i. Example: Loggerhead Sea Turtles

                     i. Must include Px survive and stay in class

                     ii. Must include Gx survive and move to next class

                     iii. *Stage-class population matrix

                     iv. Experiments by modifying fecundity or survival

         j. Assumption: Constant schedule of survival & reproduction