Identify how the physical barriers of the immune
system protect the body against pathogens.
Check all that apply.
•your nose produces oil to keep pathogens
from entering the body through your nose
•skin contains tightly packed cells
•skin is tough, flexible, and waterproof
•your cough when a pathogen enters your
mouth
•you sneeze when a pathogen enters your
nose

What is point source pollution of an aquatic ecosystem? a) pollution of freshwater sources b) pollution from many sources that combine into one c) pollution that occurs over a wide area; water that runs off from fields, parking lots, and other land surfaces d) pollution that can easily be identified with a single discharge source, such as an open pipe which drains into a body of water