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Population ecology

Explore the three types of survivorship curves, population growth patterns, and demographic transition in human population growth using graphs and mathematical equations.

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Population ecology

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  1. Population ecology Graphs & Math

  2. Survivorship Curves • 3 Types • Type I  low death rates during early/middle life; high death rates in old age • Common in animals that have few offspring • Type II  constant death rates throughout life • Type III  high death rates in the young; death rates flatten out as age increases

  3. Population Growth:

  4. Population growth : Exponential This type of graph is called a J-shaped graph

  5. Population Growth: Logistic This is called an S-shaped curve.

  6. Logistic Population Growth • Selective pressures are hypothesized to drive growth rates in 1 of 2 generalized directions: • K-selection • Density-dependent • Tends to maximize population size and operates in population living at a density near the limit imposed by their resources (like the carrying capacity) • r-selection • Density-independent • Tends to maximize the rate of increase (r); population is lower than the carrying capacity and there is little competition; usually these populations have many small offspring, have little parental care of offspring, and are in disturbed habitats • All populations are either K- or r-selected!

  7. Logistic Population Growth: Practice Problem 1. A fisheries biologist is maximizing her fishing yield by maintaining a population of lake trout at exactly 500 individuals. Predict the population growth rate if the population is stocked with an additional 600 fish. Assume that r for the trout is 0.005 individuals/(individual*day). The carrying capacity is 1000 fish. dN/dt = rmaxN[(K-N)/K] dN/dt = growth rate rmax = rate K = carrying capacity N = total population 2. Suppose a population of butterflies is growing according to the logistic equation. If the carrying capacity is 500 butterflies, the population size is 250 butterflies, and the rmax is 0.1individuals/(individual x month). What is the maximum possible growth rate for the population? dN/dt = rmaxN[(K-N)/K] dN/dt = growth rate rmax = rate K = carrying capacity N = total population

  8. Logistic Population Growth: Practice Problems ANSWERS 1. A fisheries biologist is maximizing her fishing yield by maintaining a population of lake trout at exactly 500 individuals. Predict the population growth rate if the population is stocked with an additional 600 fish. Assume that r for the trout is 0.005 individuals/(individual*day). The carrying capacity is 1000 fish. dN/dt = rmaxN[(K-N)/K] dN/dt = (.005)(1100)[(1000-1100)/1000] dN/dt = (.005)(1100)[-.1] dN/dt = -.55 fish/day 2. Suppose a population of butterflies is growing according to the logistic equation. If the carrying capacity is 500 butterflies, the population size is 250 butterflies, and the rmax is 0.1individuals/(individual x month). What is the maximum possible growth rate for the population? dN/dt = rmaxN[(K-N)/K] dN/dt = (.1)(250)[(500-250)/500] dN/dt = (.1)(250)[.5] dN/dt = 12.5 individuals/month

  9. Populations have regular Fluctuations • This is due to the interaction between biotic and abiotic factors

  10. Human Population Growth: Demographic transition • A regional human population growth can exist in 1 of 2 configurations to maintain population stability • Have high birth rates and high deaths rates OR • Have low birth rates and low death rates

  11. Human Population Growth: Age-Structure Pyramids

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