Post on 17-Jan-2016
The number of organisms per unit areaDispersion: The pattern of spacing a population within an area3 main types of dispersion
Clumped Uniform Random
The primary cause of dispersion is resource availability
How fast a population grows Factors that influence this are:
Birth rate Mortality Emigration Immigration
A limiting factor places an upper limit on the size of a population. Limiting
factors can be biotic (for example, lack of food) or abiotic
(for example, access to water).
Every species is able to survive within a range of abiotic
factors such as temperature, light, and soil. This range is
called the species’ tolerance range.
Abiotic Limiting factors include:
Temperature
Rain fall
Nutrients
the maximum, equilibrium number of organisms of a particular species that can be supported indefinitely in a given environment.
Abbreviation: K
Density Independent Factors
Affect population regardless of size or distribution
Usually abiotic
Examples: drought, fire, flood…
Density Dependent Factors
Usually biotic
Examples: Predation, parasites, disease
Which would you choose? An employer offers you two equal jobs for one
hour each day for fourteen days. The first pays $10 an hour. The second pays only 1 cent a day, but the rate
doubles each day. Which job will you accept?
Population Ecology: Population Growth Rate
Ten dollar flat rate
Lag
Final payment
Population growth modelsExponential growth model
J-curve Grows slowly at first “lags” After lag grows very fast! (exponentially) Example: Bacterial growth
Population Ecology: Population Growth Rate
We will probably reach our carrying capacity.
Our growth rate will start to look like most organisms, which is the Logistic Growth Model
Carrying Capacity (k)
What letter does this curve kind of look like?
Logistic Growth Model Often called the S-shaped growth curve Occurs when a population’s growth slows or stops
following exponential growth. Growth stops at the population’s carrying capacity
Population Ecology: Population Growth Models