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IntroBio-14-Ecology - Ecology 1 I Ecology Scientific study...

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Ecology 1
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I. Ecology Scientific study of the interactions between organisms and their environment Review : Species, population, community, ecosystem, biosphere 2
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A. Biotic factors All the organisms in the environment 3
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B. Abiotic factors Non-living (chemical and physical) factors: Temperature Water Sunlight Wind Rocks and soil 4
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II. Population ecology Studies populations in relation to the environment 5
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A. Population density Number of individuals of a species per unit area or volume Use of sampling techniques instead of counting every single individual ( mark-recapture method ) 6
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B. Dispersion patterns Pattern of spacing of individuals within their area 7
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1. Clumped Individuals aggregate in patches 8
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2. Uniform Individuals are evenly spaced 9
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3. Random Individuals are spaced in an unpredictable pattern 10
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III. Population growth Growth of a population is equal to number of births minus number of deaths 11
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A. Exponential growth Rapid increase in numbers of individuals under ideal conditions (no limit on natural resources) Constant rate of increase results in a J-shaped growth curve 12
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13
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14
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B. Logistic growth In real life a population may grow exponentially for a while There is a limit to the number of individuals an environment can support 15
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Each population has its carrying capacity (maximum size of the population that the environment can support) The logistic growth produces an S- shaped growth curve 16
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17
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IV. Limiting factors A. Density-dependent limiting factors Conditions or events that lower reproductive rates and get worse with overcrowding (food supply, wastes, disease) 18
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B. Density-independent limiting factors Conditions or events that lower reproductive rates but their effects do not vary with crowding Environmental factors (fire, flood, storms, habitat disruption) Climate; seasonal changes in weather 19
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V. Human population growth 20
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  • Fall '09
  • Drazkiewicz