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Understanding Population Growth Cycles and Stresses

Explore the dynamics of population growth, from biotic potential to environmental resistance, and learn about the concepts of intrinsic rate of increase and carrying capacity. Discover the reproductive patterns of r-selected and K-selected species and the roles of bottom-up and top-down regulation in population dynamics. Dive into survivorship curves and their implications on different populations.

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Understanding Population Growth Cycles and Stresses

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  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

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

  7. 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

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

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

  10. S or K-Curve Fluctuations

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

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

  13. 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)

  14. Video for Review

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