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Population Ecology

Population Ecology. Population Dynamics. Population Characteristics. Population Density. The number of organisms per unit area. Spatial Distribution. Dispersion is the pattern of spacing of a population. Population Ranges.

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Population Ecology

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  1. Population Ecology Population Dynamics

  2. Population Characteristics Population Density • The number of organisms per unit area Spatial Distribution • Dispersion is the pattern of spacing of a population.

  3. Population Ranges • A species might not be able to expand its population range because it cannot survive the abiotic conditions found in the expanded region. Liwi Peregrine Falcon

  4. Population-Limiting Factors • There are two categories of limiting factors—density-independent factors and density-dependent factors.

  5. 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. • Weather events • Fire • Human alterations of the landscape • Air, land, and water pollution

  6. 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. • Biotic factors • Disease • Competition • Parasites

  7. Population Growth Rate • The population growth rate (PGR) explains how fast a given population grows. • The natality of a population is the birthrate in a given time period.

  8. Population Growth Rate • A population stops increasing when the number of births is less than the number of deaths or when emigration exceeds immigration. • Immigration: movement of individuals INTO a population • Emigration: movement of individuals OUT of a population

  9. All populations grow exponentially until some limiting factor slows the population’s growth. Exponential Growth Model • J-curve; as population gets larger, it grows faster • Exponential growth occurs when the growth rate is proportional to the size of the population.

  10. Logistic Growth Model • S-curve • The population’s growth slows or stops following exponential growth, at the population’s carrying capacity.

  11. Carrying Capacity • The maximum number of individuals in a species that an environment can support for the long term is the carrying capacity. • Carrying capacity is limited by the energy, water, oxygen, and nutrients available.

  12. Reproductive Patterns • Species of organisms vary in the number of births per reproduction cycle, in the age that reproduction begins, and in the life span of the organism. • rate strategy, or r-strategy • Found in fluctuating environments, small organisms, short life spans • carrying-capacity strategy, or k-strategy • Found in stable environments, larger organisms, longer life spans

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