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r and K selected species

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Presentation on theme: "r and K selected species"— Presentation transcript:

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)

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