Examples:

1. de1:=diff(y(t), t) = a*y(t)-g*y(t)^2
s1:=dsolve({de1, y(0)=100},y(t))
s2:=subs(a=2, s1)
s3:=subs(g=2, s2)
s4:=rhs(s3)
plot(s4, t=0..1)

   

2. Now we solve the same problem but with a different value of g
   
   de1:=diff(y(t), t) = a*y(t)-g*y(t)^2
s1:=dsolve({de1, y(0)=100},y(t))
s2:=subs(a=2, s1)
s3:=subs(g=0.001, s2)
s4:=rhs(s3)
plot(s4, t=0..5)

   

   Note: All that changed in the ODE for this example is g but the graph is drastically different.