chapter 6 population and community ecology
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Chapter 6 Population and Community Ecology. Nature exists at several levels of complexity. Evolution. Natural Selection. Ecosystem, Community, Population, Species, Individual??. Community. A forest that includes maple, beech and hemlock trees. - PowerPoint PPT PresentationTRANSCRIPT
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Chapter 6Population and Community Ecology
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Nature exists at several levels of complexity
Natural Selection
Evolution
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Ecosystem, Community, Population, Species, Individual??•A forest that includes maple, beech
and hemlock trees.•A bear population preying on a fish
population in a river with high sunlight
•A single blue jay sitting on a telephone wire.
•A pride of lions that lives in a particular region of Africa.
Community
Individual
Population
Ecosystem
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Population Ecology• Populations are dynamic• Difference is between inputs and outputs• Why is population ecology important?
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Factors that Regulate Population Abundance and Distribution• Population size (N)- the total number of individuals within a defined area at a given time.
• In 1987, California Condor had N = 22• Population ecologists caught all 22, in 2009, N = 300
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Factors that Regulate Population Abundance and Distribution
• Population density- the number of individuals per unit area at a given time.
• Helps scientists figure out if species is rare or abundant
• Management zones – typically more hunting/fishing licenses for area with high pop. density
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Factors that Regulate Population Abundance and Distribution
• Population distribution- how individuals are distributed with respect to one another.
• Random – no pattern
• Uniform – common in territorial organisms, toxic plants
• Clumped – schooling fish, flocking birds, herd animals
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Factors that Regulate Population Abundance and Distribution
• Population sex ratio- the ratio of males to females- Typically 50/50- Helps predict number of offspring in the next
generation
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Factors that Regulate Population Abundance and Distribution
• Population age structure- how many individuals fit into particular age categories.- Helps predict how rapidly a population can
grow.
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Factors that Influence Population Size
•Density-dependent factors- the size of the population will influence an individual’s probability of survival. - Examples: amount of available food
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Factors that Influence Population Size•Gause’s experiment demonstrates
how food supply controls population growth•Limiting resources- Examples: food, waternest sites, nitrogen, phosphorus
•Carrying capacity (K)
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Factors that Influence Population Size
•Density-independent factors- the size of the population has no effect on the individual’s probability of survival. - Example: tornado, hurricanes, floods,
fires