Dispersion spatial distribution of individuals within a population

Dispersion spatial distribution of individuals within a population

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 • Three types of dispersion.

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

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

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

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

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

Dispersion spatial distribution of individuals within a population