Population Models
Key Questions

Population dynamics is a subject under the broader study of dynamic systems. This is studied under life sciences that studies the size and age composition of populations.
That includes human populations or even populations of bacteria, or just any other organism.

Answer:
Exponential model of population growth describes the volume of population (number of species) as an exponential function of time similar to:
#P=a*b^(c*T)#
where#a,b,c#  are constants,#T#  time.Explanation:
Imagine you have bacteria that divides into 2 every hour.
If at#T=0# we have one such bacteria, at#T=1# (in an hour) we will have two of them, at#T=2# (in two hours) we will have 4 of them etc.
At any time#T# we will have the number of bacteria equal to
#P=2^T# The above is a typical exponential growth of a population. The number of offsprings and other parameters can modify the formula, but it still will be based on exponential function with the time parameter in the exponent.
Obviously, real life conditions introduce complications in the formula based on variable productiveness and mortality rates.