In Vertebrates, Complement Activation Generally Involves a Pathogen Recognition Step

Essay

In vertebrates, complement activation generally involves a pathogen recognition step followed by a proteolytic cascade that produces the effector proteins that function in opsonization, membrane attack, and inflammation.
a) Which of these is likely to be the most evolutionarily primitive aspect of the complement system?
b) Which pathway of complement initiation is likely to be the one that most recently evolved?