populations. population density the number of organisms in a population per unit area. ex. 5 snakes...
DESCRIPTION
Growth Rate Change in population size over time Positive growth rate- population is increasing Negative growth rate- population is decreasing Zero growth rate- population size is not changing Population size Time Population size Time Positive Negative Population size Time ZeroTRANSCRIPT
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Populations
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Population Density• The number of organisms in a population per unit area. • Ex. 5 snakes per square mile• Ex Tigers low density, mosquitoes high density
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Growth Rate• Change in population size over time• Positive growth rate- population is increasing• Negative growth rate- population is decreasing• Zero growth rate- population size is not changing
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Negative
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Exponential Growth• Population will increase exponentially (J-curve)• Not realistic because as population increases
resources become limited. (ex food shortage)
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Logistic Growth• Starts out exponential, but levels off at a certain population
size (S-curve)• Carrying Capacity- the maximum population size an
ecosystem can support, leveling off point• Ex. goldfish in a tank
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R vs. K• R-selected species- reproduce fast, have many
young, develop quickly. (rabbits)• K-selected species- reproduce steadily, have few
young develop slowly. (kangaroos)
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Density Dependant Factors• Factors that have a greater influence on population size as
the population increases• Generally biotic factors• Ex. competition, predation, parasitism, crowding stress
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Density Independent Factors• Factors that have an impact on population size regardless of
what the population size is.• Generally abiotic factors• Ex. weather, fires, drought, human activities
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SuccessionSuccession- changing of plant communitiesPrimary succession- begins with bare rock from volcanic
activity ex. Rock- moss – grass- shrubs –forest
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Secondary succession- begins with soil from a previous community ex. Fire -Soil- grass- shrubs-forestPioneer community- first community (ex: moss,grass)Climax community- ending community (ex: forest)
Secondary Succession