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Population Growth

Population Growth. Chapter 35. Population Density/Population Dispersion Fig 35.2 B&C p. 701. Density - mathematical expression of the number of individuals of a species in a given area Dispersion - description of the pattern of spacing of individuals within that area Clumped Uniform

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Population Growth

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  1. Population Growth Chapter 35

  2. Population Density/Population Dispersion Fig 35.2 B&C p. 701 • Density - mathematical expression of the number of individuals of a species in a given area • Dispersion - description of the pattern of spacing of individuals within that area • Clumped • Uniform • Random

  3. Limiting Factors on Population Growth • Density-Dependent • Intraspecific competition - individuals of the same population compete for food, resources, space • Become more acute as the population increases • Territoriality - a behavior that excludes others of the same species from a defined area

  4. Limiting Factors on Population Growth • Density-Independent • Independent of population size • Weather • Predators

  5. Population Growth • Equation for exponential population growth: dN/dt = rN • dn/dt = change in population with time • rN = (bN - dN) • Common sense: Difference between birth rate and death rate • So, the equation dN/dt = rN may be read as • The change in population with time is equal to the difference between the birth rate and the death rate

  6. Carrying Capacity p. 703 • Maximum population supported by an ecosystem over a sustained period of time. • New equation for population growth: • dN/dt = rN([K-N]/K) • Where ([K-N]/K) is the difference between the carrying capacity and the population size • When K - N = 0, the population increase is 0 • The population remains fairly stable…at its carrying capacity!

  7. Growth Curves Fig. 35.3A p. 702 • Population growing at a logarithmic rate

  8. Growth Curves Fig. 35.3 B&C p. 703 • Population in equilibrium at its carrying capacity.

  9. human Hydra oyster Survivorship Curves Fig 35.6 p. 706 • Humans - high survivorship early in life • Oysters - low survivorship early in life • Hydra- fairly uniform survivorship

  10. Demography • Study of the generational percentages within a population • Demographic “pyramids” used to describe health of a population, birth & mortality rates

  11. In the following Fig 35.9B p. 711:- Note how Sweden’s cohorts are fairly equal; one cohort is replacing the other and the populaton is remaining stable.- Mexico’s population is increasing geometrically.- USA’s is still increasing, but becoming more stable.

  12. Demographic structures SWEDEN MEXICO USA

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