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Population Dynamics Population Characteristics Population Density number of organisms per unit area Population Dispersion the pattern of spacing of a population within an area 3 Types of Population Dispersion Interactive: Visualizing Population Dispersion Population Growth Population Growth Rate (PGR) explains how fast a given population grows = ( ( Change in population size Births + Immigration -( ( Deaths + Emigration Immigration = movement INTO a population Emigration = movement OUT OF a population (think EXIT) Population Growth Population Growth Rate (PGR) Equation Solve This: In the year 2000, the population of Douglasville was 20,065. In the year 2010, the population of Douglasville was 30,961. How much did the population grow during this 10 year period? Use the Population Growth Rate Equation to figure this out! Answer: 30,961 – 20,065 X 100 = 54% 20,065 Exponential (Unrestricted) Growth The growth of the population accelerates at a rapid pace There is no limit on the population size … yet Shape is described as a J-Curve What stops or slows population growth? Limiting Factors Any abiotic or biotic factor that restricts the numbers, reproduction, or distribution of organisms Examples: – sunlight, climate, temperature (abiotic factors) – food supply (prey), predation, competition (biotic factors) Limiting Factors 2 types of limiting factors Density-dependent limiting factors Density-independent limiting factors Density-Dependent Factors Any factor that depends on the size of a population Examples: - Predation - Disease (High population = easy transmission) - Parasites - Competition (As competition increases, resources such as food or space decrease, or become limited) Competiton: Wolf vs. Moose One’s growth depends on the other’s population Density-Independent Factors Any factor that DOES NOT depend on the size of a population Examples: – Flooding – Drought – Tornadoes – Fire – Pollution – Human alterations to the landscape Carrying Capacity The maximum number of individuals in a species that an environment can support for the long term Carrying Capacity Rate of population growth slows down because of the influence of limiting factors. Logistic Shape Growth is described as an S-Curve Carrying Capacity Graphs What is the carrying capacity? Carrying Capacity What is the carrying capacity? Carrying Capacity What is the carrying capacity? Carrying Capacity What is the carrying capacity? of snowshoe hare of lynx