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Chapter 6 Population and Community Ecology

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.

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Chapter 6 Population and Community Ecology

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  1. Chapter 6 Population and Community Ecology

  2. Nature exists at several levels of complexity Evolution Natural Selection

  3. Ecosystem, Community, Population, Species, Individual?? Community • 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. Ecosystem Individual Population

  4. Population Ecology • Populations are dynamic • Difference is between inputs and outputs • Why is population ecology important?

  5. 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

  6. 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

  7. 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

  8. 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

  9. 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.

  10. 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

  11. Factors that Influence Population Size • Gause’s experiment demonstrates how food supply controls population growth • Limiting resources • Examples: food, water nest sites, nitrogen, phosphorus • Carrying capacity (K)

  12. 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

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