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Understanding Population Ecology: Factors, Growth, and Distribution

Learn about population ecology characteristics such as density, spatial distribution, and growth rate. Explore population-limiting factors and the impact of density-independent and density-dependent factors. Understand population growth models and carrying capacity in different species.

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Understanding Population Ecology: Factors, Growth, and Distribution

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  1. Populations are described by density, spatial distribution, and growth rate. Population Ecology

  2. Population Characteristics • Populations are groups of the same species in the same area. • Characteristics of population include: • Density • Spatial Distribution • Growth rate

  3. Population density • The number of organisms per unit area is population density.

  4. Spatial distribution • Dispersion is the pattern of spacing of individuals of a population within an area. • Three kinds: clumped, uniform, and random

  5. Population-Limiting Factors • Limiting factors are biotic or abiotic forces that keep population from increasing indefinitely. • Limiting factors are either density-independent or density-dependent.

  6. Density-independent factors • Any factor in the environment that does not depend on the number of members in a population per unit area is a density-independent factor. • Usually abiotic, and include: • Weather events • Fire • Human alteration of the landscape • Air, land, and water pollution

  7. Density-dependent factors • Any factor in the environment that depends on the number of members in a population per unit area is a density-dependent factor. • Often biotic, and include: • Predation • Competition • Disease • Parasites

  8. Population growth rate • The population growth rate (PGR) describes how fast a given population grows. • Natality: birthrate of a population in a given year. • Mortality: death rate of a population in a given year • Emigration: number of individuals moving away from the population • Immigration: number of individuals moving into a population

  9. Births Deaths Deaths and emigrationremove individualsfrom a population. Births and immigrationadd individuals toa population. Immigration Emigration

  10. Exponential growth model • Occurs when growth rate is proportional to population size. • All populations grow exponentially until they encounter a limiting factor.

  11. Logistic growth model: • Occurs when a population’s growth slows or stops following exponential growth. • A population stops increasing when the number of births < number of deaths, or when emigration > immigration.

  12. Carrying capacity • Carrying capacity is the maximum number of individuals of a species (pop size) that an environment can support.

  13. Reproductive patterns • Species vary in the number of births per reproduction cycle, age that reproduction begins, and in the life span. • Plants and animals are placed into groups based on these patterns.

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