What system of the human body is prepared for defensive action

The immune system

The immune system, made up of white blood cells, is ready at all times to defend out body against any form of bacteria, virus, infection, etc.

geologic time scale (for gradpoint) =)

the wetland preservation movement began in the u.s. in earnest with the clean water act (cwa) of 1972. although not specifically written to protect wetlands, the cwa is comprised of a series of regulations designed to prevent pollutants from contaminating u.s. waters.