Final answer:
The classical pathway of the complement cascade requires the presence of antibodies to initiate the response, while the alternative pathway is antibody-independent.
Step-by-step explanation:
The classical pathway of the complement cascade is the only pathway that requires the presence of antibodies to initiate the response. In this pathway, the complement protein C1 binds to an antigen-antibody complex on an invading pathogen, which triggers the activation and binding of other complement proteins. This leads to the formation of destructive pores in the pathogen's cell envelope and cell wall.
The alternative pathway, on the other hand, does not require antibodies for activation and is spontaneously activated by the protein C3.