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immunology

(Encyclopedia)immunology, branch of medicine that studies the response of organisms to foreign substances, e.g., viruses, bacteria, and bacterial toxins (see immunity). Immunologists study the tissues and organs of...

infection

(Encyclopedia)infection, invasion of plant or animal tissues by microorganisms, i.e., bacteria, viruses, viroids, fungi, rickettsias, and protozoans. The invasion of body tissues by parasitic worms and other higher...

pesticide

(Encyclopedia)pesticide, biological, physical, or chemical agent used to kill plants or animals that are harmful to people; in practice, the term pesticide is often applied only to chemical agents. Various pesticid...

vaccination

(Encyclopedia)vaccination, means of producing immunity against pathogens, such as viruses and bacteria, by the introduction of an killed or weakened microorganism, a harmless piece of a microorganism, or the like t...

immunity

(Encyclopedia)immunity, ability of an organism to resist disease by identifying and destroying foreign substances or organisms. Although all animals have some immune capabilities, little is known about nonmammalian...

Annelida

(Encyclopedia)CE5 A. The earthworm, Lumbricus terrestris, representative of the phylum Annelida. B. Internal anatomy of an earthworm. Annelida ənĕlˈĭdə [key] [Lat., anellus=a ring], phylum of soft-bodied, ...