1. r and K selected species

2. No Population Can Grow Indefinitely: J-Curves and S-Curves
Biotic potential – capacity for population growth under ideal conditions
Larger organisms tend to have low potential

3. Population Growth
Exponential growth – population that increases at a fixed rate
J-Curve
Logistic growth – rapid exponential population growth followed by a steady decrease in population growth
S-Curve

4. Population Growth

5. J-Curves
Intrinsic rate of increase (r) – rate the population of a species would grow if it had unlimited resources

6. J-Curves Individuals in populations with high r
Reproduce early in life
Have short generation times
Can reproduce many times
Have many offspring each time they reproduce

7. S-Curves
Environmental resistance – combination of all factors that act to limit the growth of a population
Carrying capacity (K) – maximum population of a given species that a habitat can sustain indefinitely without being degraded

8. S-Curves

9. Phases of Logistic Growth Curve
Lag Phase – little initial growth.
Rapid Growth Phase
Stable Phase – stabilizing factors limit growth

10. Species Reproductive Patterns
r-Selected species, opportunists – species with a capacity for a high rate of population increase
Many small offspring
Little to no parental care or protection
Reproductive opportunists
K-selected species, competitors – reproduce later in life and have a small number of offspring with fairly long life spans
Few large offspring
High parental care

11. Positions of r- and K-Selected Species on the S-Shaped Population Growth Curve

12. Transitioning between J and S curves…
Carry capacity isn’t fixed
Varies depending on climate and season
Unpredictable changes can be devastating to the species AND the habitat
Reproductive time lag – period needed for the birth rate to fall and the death rate to rise in response to resource overconsumption
May lead to overshoot
Dieback (crash)

13. r-Curve Fluctuations

14. Types of Population Change
Stable – population fluctuates slightly above and below its carrying capacity
Characteristic of undisturbed rain forests
Late loss curve
Irruptive – short-lived rapidly reproducing species
Linked to seasonal changes in weather or nutrient availability
Algal Blooms
Early loss curves

15. S-Curve Fluctuations

16. Types of Population Change
Cyclic fluctuations, boom-and-bust cycles
Top-down population regulation
Controlled by predation
Bottom-up population regulation
Controlled by scarcity of one or more resources
Irregular – changes in population size with no recurring pattern
chaos

17. Top-down Regulation

18. Your Turn! Make a K selected  r selected continuum on your desk
Organize your cards ON YOUR OWN
Discuss with partner

19. Survival Strategies
Which organisms were difficult to classify? Why?

20. Survival Strategies K selected r selected Red-tailed hawk Coyote
Western rattlesnake
Roadrunner
Kangaroo Mouse
Whiptail lizard

21. Your Turn! Live for Today Life Table Review:
What does late loss look like?
What does early loss look like?
What does constant-loss look like?
Remember to include a key (molting species)