Dispersion spatial distribution of individuals within a population

Three types of dispersion. Clumped resources or living space are clumped, or because of social behavior

Three types of dispersion. Uniform (Even) social interactions result in individuals getting as far away from each other as possible

Three types of dispersion. Random Ex: seed dispersal by winds or birds

Understanding Populations Population size # of individuals it contains 14.3 Population Density and Distribution Understanding Populations Population size # of individuals it contains Population density How crowded a population is # of individuals/unit of area or volume

Measuring Populations 14.4 Population Growth Patterns Measuring Populations Population Dynamics change in size and composition over time Birth rate, death rate, life expectancy Population Growth Rate Depends on birth, death, emigration (movement out of a population), and immigration (movement into a population)

14.4 Population Growth Patterns Survivorship curves show the number of surviving members over time from a measured set of births.

14.4 Population Growth Patterns Exponential Model Increases rapidly after only a few generations Assumption Birth rates & death rates remain constant no matter how large the population becomes Populations cannot grow indefinitely because of availability of resources and accumulation of wastes

14.4 Population Growth Patterns Logistic Model Accounts for the influence of limiting factors Limiting factor – restrains the growth of a population Birth rates decline and death rates rise as population grows Carrying capacity – the # of individuals the environment can support over a long period of time the birth rate equals the death rate and growth stops Assumption Carrying capacity is constant and does not fluctuate with environmental changes

14.4 Population Growth Patterns Logistic and exponential models are not accurate representations of real populations They are tools used to study population growth and regulation

Population Regulation – Limiting Factors 14.4 Population Growth Patterns Population Regulation – Limiting Factors Density-independent factor – weather, floods, and fires Reduce the population by the same proportion regardless of population size Density-dependent factor – food shortages or nesting sites Triggered by increasing population density

14.5 Ecological Succession KEY CONCEPT Ecological succession is a process of change in the species that make up a community.

14.5 Ecological Succession a sequence of biotic changes damaged communities are regenerated new communities arise in previously uninhabited areas

14.5 Ecological Succession There are two types of succession. primary succession — started by pioneer species

14.5 Ecological Succession There are two types of succession. 2. secondary succession — started by remaining species