In the reaction b+k =l+h if an additional b is added the result will be

In the given reaction, B + KL + H, the effect of adding further B is that it favors the forward reaction which means more products will be produced upon the addition. This obeys Le Chatelier's principle which states that any disturbance incurred to the equilibrium system shall be dealt such that the disturbance is countered to and attain equilibrium again.

It is evolution, because we all have some of the same traits like eye color or shape or ears.