Ecology

Ecology- the study of the interactions between organisms and their enviorment. 4 levels:
1. Population- a group of individuals of the same species living within the same area. (Territory)
     2. Community- all of the populations that interact within a given area.
     3. Ecosystem- community plus all the abiotic- nonliving, factors that affect it.
     4. Ecosphere- gloabl ecology

Population Ecology
I. Population Dynamics- How populations change.
    A. Growth- what factors affect it?
         1. Emmigration (-) Movement out
         2. Immigration (+) Movement into
         3. Natality (+) Birth Rate
         4. Mortality (-) Death Rate
    B. Growth Rates- 3 types
         1. Arithmetic- same amount of increase within each growth period. Bad way to calculate growth. 
           

          2. Exponential- population grows by the same percent (%) each year. Use this when a population is small with lots of room to grow. (J-shaped curve)

            equation: delta N/delta t = rN
             delta N= change in # (unknown)
             delta t= change in time
             r= % rate (convert % to decimal)
             N= current #

Example:
cattle herd; 2011= 50, 2012=60, 2013= ?

delta N/1= rN

delta N= (.2)(60) = 12     60+12= 72

       3. Biological- population will eventually slow down and stop due to resource limitations.Eventually it will reach its carrying campacity- the maximum number a given enviorment can support on a long-term basis.
(S-shaped cuve)


Equation
 delta N/ delta t= rN(K-n/K)
K= carring capacity

Example:
cattle herd; 2011= 50, 2012=60, 2013=?

=(.2)(60)(100-60/100)
=(12)(.4)
=4.8 round to 5
=2013=65