Logistic model is a growth model which is also called S shaped or sigmoidal growth model
This type of model mainly depends upon the carrying capacity of a given area and they invest their most energy in maintenance rather than reproduction
Logistic model is represented by :
[tex]dN/dT=rN(K-N/K)[/tex]
where, r= reproductive rate; K= carrying capacity; N= initial population
Lotka Volterra model
It is the model which describes the prey predator relationship
Here it is expressed in the form of mathematical equations which helps in prediction of relationship between two species
For species 1, equation is represented as:
[tex]dN1/dT1=r1N1(K1-N1-\alpha N2/K1)\\[/tex]
here,[tex]\alpha[/tex] is the inhibitory effect of species 2 on species 1; r1 is the intrinsic growth rate; N1 is initial population of species 1; K1 is the carrying capacity of species 1; N2 is the initial population of species 2
For species 2, equation is represented as:
[tex]dN2/dT2=r2N2(K2-N2-\beta N1/K2)[/tex]
here, [tex]\beta[/tex] is the inhibitory effect of species 1 on species 2; r2 is the intrinsic growth rate of species 2; N2 is the initial population of species 2; K2 is the carrying capacity of species 2; N1 is the initial population of species 1
There are certain conditions which helps us to determine the relationship between two species:
If K2> K1/[tex]\alpha[/tex] or K1> K2/[tex]\beta[/tex] then there will be unstable coexistence between species 1 and species 2
If K2< K1/[tex]\alpha[/tex] or K1< K2/[tex]\beta[/tex] then there will be stable coexistence between species 1 and species 2