function dYdt = lotka_ode(t,Y)
% assume 'Y' is a vector of form Y = [x; y; z];

x = Y(1);
y = Y(2);

global alpha beta delta gamma c

prey = x.*(alpha - (y./beta)) - c.*x^2;
pred = -y.*(gamma - (x./delta)) ;

dYdt = [prey; pred];  
 

     