The following three differential equations are used to model a combined predator–prey and competing species system:

˙ x = x(a10 − a11x + a12y − a13z),

˙ y = y(a20 − a21x − a22y − a23z),

˙z = z(a30 + a31x − a32y − a33z), where aij are positive constants. Give a physical interpretation for the terms appearing on the right-hand sides of these differential equations.