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Population Dynamics E.Q. What are the factors that affect a population in an ecosystem? Population characteristics • • • • Population density Population range Population growth rate Population limiting factors – Density-independent – Density-dependent • Spatial distribution or dispersion – Uniform – Clumped – Random • Map shows Current (dark green) and Historic Range (light green) of Grizzly Bears in North America • What is your best hypothesis about the reasons for the change in the population range of grizzly bears in North America? • What geographical feature seems to most strongly determine the population range of the grizzly bear? Population characteristics • Population density – the number of an organism (species) that lives in a unit area (acre, square mile, 100 square miles, etc.) • Spatial distribution or dispersion – the pattern of spacing of a population in an area Population characteristics dispersion patterns • (a) Clumped dispersion - certain animal species are grouped in herds; plant species sometimes grow around specific features like ponds or lakes • (b) Uniform dispersion – certain animal species are territorial; some plant species produce a same species toxin that limits reproduction or settlement within a given range • (c) Random dispersion – members of a population are distributed in a random fashion that is unrelated to the presence of others Population characteristics • Population range – the geographical area in which an organism or population can live – Limited by abiotic factors such as temperature, humidity, rainfall, sunlight – Limited by biotic factors such as competitors, predators, parasites – Primary limiting biotic factor - food Map A shows Grizzly Bears in North America and Map B shows Current Range of Polar Bears in NA. Based on the maps, what can you tell about the population range and relationship between the 2 species? Map A Map B Population characteristics • Population limiting factors – factors that prevent a population from growing indefinitely – Density independent factors – anything that does not depend on the number of a population in a unit area. Usually abiotic – weather, fire, pollution – Density dependent factors – anything that does depend on the number of a population in a unit area. Usually biotic – predation, competition, disease, parasitism. Population characteristics • Population growth rate – the speed at which a given population grows • Gestation period, natality (birth rate), longevity, death rate • Emigration – individuals organisms leaving a population • Immigration – individual organisms moving into a population Population growth rate • Carrying capacity – the maximum number of a population that an environment can support long-term Population characteristics • Population density (# of species in an area) • Population range (latitude, altitude, climate, etc.) • Population growth rate (births, deaths, longevity, reproduction rate, emigration, immigration) • Population limiting factors – Density-independent (abiotic factors, weather, climate, carrying capacity) – Density-dependent (disease, competition, parasites) • Spatial distribution or dispersion – Uniform – Clumped – Random Determining populations A B C D Determining populations A B C D Determining populations A B C D How do we determine population of species in ABCD? Population in area A = 38 Total population of ABCD = 152 Determining populations A B C D Determining populations A B C D Determining populations A B C D Determining populations A B C D List the possible explanations for the change in population dispersion. Determining populations 1. Disease A B 2. Parasites 3. New predators 4. Competition 5. Climate change 6. Carrying capacity C D 7. Emigration List the possible explanations for the change in population dispersion. Quiz 1. 2. 3. 4. 5. 6. Carrying capacity Emigration Dispersion Population range Population density Immigration a. # of individuals in a population b. Individuals entering a population from outside c. Geographical area a population inhabits d. Pattern of distribution e. Population limit in an area f. Individuals leaving a population