Chapter 4 Population Ecology Section 1: Population Dynamics

The number of organisms per unit area Chapter 4 Population Ecology 4.1 Population Dynamics Population – a group of organisms of the same species that live in a particular area. Population Density The number of organisms per unit area Spatial Distribution Dispersion is the pattern of spacing of a population.

Ways to estimate size of population Quadrant: Section off a known area of the population, count the individuals in the section. Then multiply by the number of areas (plants) Capture/recapture: sampling a population to determine the size based on migration, birth rate, and death rate (animals)

Chapter 4 Population Ecology

Population-Limiting Factors Chapter 4 Population Ecology 4.1 Population Dynamics Population-Limiting Factors There are two categories of limiting factors—density-independent factors and density-dependent factors.

Density-Independent Factors Chapter 4 Population Ecology 4.1 Population Dynamics Density-Independent Factors Any factor in the environment that does not depend on the number of members in a population per unit area Weather events Fire Human alterations of the landscape Air, land, and water pollution

Density-Dependent Factors Chapter 4 Population Ecology 4.1 Population Dynamics Density-Dependent Factors Any factor in the environment that depends on the number of members in a population per unit area Biotic factors (food available) Disease Population Biology Competition

4 factors that affect the size and composition of a population : Chapter 4 Population Ecology 4.1 Population Dynamics 4 factors that affect the size and composition of a population : Natality: birthrate Mortality: death rate Immigration: Individuals moving into a population Emigration: individuals leaving the population

Exponential Growth Model Chapter 4 Population Ecology 4.1 Population Dynamics Exponential Growth Model All populations grow exponentially until some limiting factor slows the population’s growth.

Chapter 4 Population Ecology 4.1 Population Dynamics Logistic Growth Model population’s growth slows or stops following exponential growth, at the population’s carrying capacity.

Zero population growth: when birth rate equals death rate Chapter 4 Population Ecology 4.1 Population Dynamics A population stops increasing when the number of births is less than the number of deaths or when emigration exceeds immigration. Zero population growth: when birth rate equals death rate

Chapter 4 Population Ecology 4.1 Population Dynamics 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.

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