Population Dynamics

Properties of populations Size: # of individuals it contains Dispersion: spatial distribution of individuals in a population. Clumped Even Random Density: how crowded a population is

Population Dynamics Birth rate: # of births Death/Mortality rate: # of death Life Expectancy: avg. life span an individual is expected to live.

Population Growth Rate Growth rate: amount by which a populations size changes over time. Growth rate depends on: births, deaths, emigration and immigration. Which 2 add to the population, which 2 take from the population?

Exponential Model of Growth When a population increases rapidly after only a few generations; the larger the population gets the faster it grows. Has a J shape (See blue line)

Logistic Growth Builds on exponential growth but takes in account limiting factors. Has an S shape (see red line)

Limiting Factors populations cannot grow indefinitely because the resources they depend on become scarce and waste accumulate. Competition becomes an issue as a pop. grows. As resources decrease the ability of individuals to fight off disease, grow and reproduce reduces.

Density Independent factors A limiting factor that controls size. Includes: Natural Disaster (Floods, Fires) Human Impact Weather

Density Dependent factors Are resource limitations. Include: Competition Predation Parasitism/Disease Carrying Capacity: the total amount of individuals that an environment can sustain (hold)