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Interdependence of Life: Introductions to Populations

BioEd Online. Interdependence of Life: Introductions to Populations. By Deanne Erdmann, MS Evan Siemann, Ph.D. BioEd Online. Populations. Definition: Groups of organisms of the same species that live within a given area Key characteristics: Growth rate Population density

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Interdependence of Life: Introductions to Populations

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  1. BioEd Online Interdependence of Life: Introductions to Populations By Deanne Erdmann, MS Evan Siemann, Ph.D.

  2. BioEd Online Populations • Definition: Groups of organisms of the same species that live within a given area • Key characteristics: • Growth rate • Population density • Dispersion patterns Ostriches are nomadic, wandering in small groups. Aspen trees are quick to pioneer areas that have been disturbed by fire.

  3. BioEd Online Population Growth Types of Growth: Exponential vs. Logistical Growth Factors Affecting Growth • Birth rate • Death rate • Immigration • Emigration

  4. BioEd Online Limits on Population Growth • Density Dependent Limiting Factors • Food • Water • Shelter • Disease • Density Independent Limiting Factors • Weather • Climate • Human Disturbances Water and shelter are critical limiting factors in the desert. Fire is an example of a Density independent Limiting factor.

  5. r- Selected (maximum growth rate, below carrying capacity) Early reproduction Short life span High mortality rate Little or no parental care Large investment in producing large numbers of offspring Tend to occur in unpredictable environments Examples: Bony fish Grasshoppers K-Selected (maximizes population size near carrying capacity) Late reproduction Long life span Low mortality rate Extensive parental care Greater investment in maintenance and survival of adults At or near carrying capacity Experience effects of population density Examples: Sharks Elephants BioEd Online Reproductive Strategies

  6. BioEd Online Survivorship in Populations • Survivorship curves graphically represent the age structure of a given population. We use them to predict future population growth.

  7. Human Population Growth • Human population growth does not currently show density effects that typically characterize natural populations. • Human population growth rate has been growing more than exponentially. • Limited resources eventually will cause human population growth to slow, but global human carrying capacity is not known.

  8. Population Age Structure • Differences in environmental conditions and past history may cause populations to differ in their age distributions. • The future growth of a population depends on its current age distribution.

  9. BioEd Online Population Density • Population density is total population size per unit of area. • Population densities depend on: • Interactions within the environment • Quality of habitat • Density-dependent factors • Density-independent factors • Carrying capacity is the maximum number of organisms that can be supported in a given habitat.

  10. BioEd Online Dispersion Patterns Within Populations Three common patterns of population distribution are:

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