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Published byEllen Heath Modified over 9 years ago
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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 Population size Time Population size Time Positive Negative Population size Time Zero
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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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Succession Succession- changing of plant communities Primary 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-forest Pioneer community- first community (ex: moss,grass) Climax community- ending community (ex: forest) Secondary Succession
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