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R and K selected species. No Population Can Grow Indefinitely: J-Curves and S-Curves Biotic potential – capacity for population growth under ideal conditions.

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Presentation on theme: "R and K selected species. No Population Can Grow Indefinitely: J-Curves and S-Curves Biotic potential – capacity for population growth under ideal conditions."— 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 1.Lag Phase – little initial growth. 2.Rapid Growth Phase 3.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 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) Transitioning between J and S curves…

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 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 Types of Population Change

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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