Population Growth Cycles and Stresses

1. Population Growth Cycles and Stresses Chapter 5 Section 2

2. Population Growth

3. No Population Can Grow Indefinitely: J-Curves and S-Curves Biotic potential – capacity for population growth under ideal conditions Intrinsic rate of increase (r) – rate the population of a species would grow if it had unlimited resources

4. Population Stresses Any population growing exponentially goes through a “J” shaped growth, but most of the time environmental influences create an “S” shaped pattern in growth

5. 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

7. This shows exponential growth leading to overshoot and population dieback of a species

8. 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

9. r- and K- selected Organisms Courtesy of www.bio.indiana.edu

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

11. S or K-Curve Fluctuations

12. r-Curve Fluctuations Bottom-up Regulation: Population is limited by available resources (boom and bust cycle)

13. Top-down Regulation Predation keeps both populations within the limits of available resources

14. Survivorship Curves These curves demonstrate • Type I: Late Loss Populations (K – strategists) • Type II: Constant Loss Populations (K – strategists) • Type III: Early Loss Populations (usually r-strategists)

15. Video for Review