14 3 Population Density And Distribution Dispersion spatial

14. 3 Population Density And Distribution Dispersion spatial distribution of individuals within a population

14. 3 Population Density And Distribution • Three types of dispersion. 1. Clumped – resources or living space are clumped, – or because of social behavior

14. 3 Population Density And Distribution • Three types of dispersion. 2. Uniform (Even) • social interactions result in individuals getting as far away from each other as possible

14. 3 Population Density And Distribution • Three types of dispersion. 3. Random • Ex: seed dispersal by winds or birds

13. 1 Population Ecologists Study Relationships 14. 3 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. 3 Population Density 14. 4 Population Growth Patterns And Distribution 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. 3 Population Density 14. 4 Population Growth Patterns And Distribution Survivorship curves • show the number of surviving members over time from a measured set of births.

14. 3 Population Density 14. 4 Population Growth Patterns And Distribution 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. 3 Population Density 14. 4 Population Growth Patterns And Distribution 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. 3 Population Density 14. 4 Population Growth Patterns And Distribution • Logistic and exponential models are not accurate representations of real populations • They are tools used to study population growth and regulation

14. 3 Population Density And Distribution

14. 3 Population Density 14. 4 Population Growth Patterns And Distribution 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. 3 Population Density And Distribution 14. 5 Ecological Succession KEY CONCEPT Ecological succession is a process of change in the species that make up a community.

14. 3 Population Density And Distribution 14. 5 Ecological Succession – a sequence of biotic changes – damaged communities are regenerated – new communities arise in previously uninhabited areas

14. 3 Population Density And Distribution 14. 5 Ecological Succession • There are two types of succession. – primary succession — started by pioneer species

14. 3 Population Density And Distribution 14. 5 Ecological Succession • There are two types of succession. 2. secondary succession — started by remaining species