The Nature of Disease Causing Organisms :: essays research papers

The nature of DISEASE CAUSING ORGANISMS and the mechanisms employed by man to combat these organisms. What is disease? A disease is a disturbance in the normal structure or function of an organism, group of organisms or the entire body. Diseases affect different organisms in different ways, they may be temporary, they may be chronic, or they may be terminal. They may even be localized or widespread through an entire body. Many diseases have been eradicated, but, some have no cure. Humans and other vertebrates have a system of specific immunity to combat disease. Some disease causing organisms invade body tissues and then destroy them, while others setup a symbiotic relationship with the cells. Most communicable diseases are caused by microorganisms or larger parasites that are commonly called germs, most scientists call them pathogens. What kinds of disease are there, that are caused by organisms? -Infectious disease- caused by living organisms, can be passed by contact. -Viral disease- caused by viruses, difficult to treat because viruses are non-living -Fungal disease- usually cause mild infections, difficult to treat -Protozoan disease- the "tropical diseases" caused by protozoa -Worm infections- mostly in the tropics, worms inside body causing damage -Diseases can be caused by a wide variety of bacteria, viruses, fungi, protozoans, and parasitic worms. Some sferre some disease causing organisms, and how do they affect plants? Plant diseases can be caused by microorganisms, parasitic flowering plants, nematodes, viruses, or adverse environmental conditions. Bacterial diseases are marked by symptoms such as soft rot, leaf spot, wilt of leaves and roots, cankers, leaf and twig blight, and gall formation. Most plant diseases are caused by fungi. Fungal diseases have been documented on since biblical times. Fungal diseases are characterized by leaf spots, ulcerous lesions, blights, powdery mildew, cankers, root rots, wilts, and club root. Viral diseases are infectious and spread largely by insects. All economic plants suffer from one or more viral diseases. Symptoms include mosaic patterns, yellowing of foliage, vein clearing, ring spots, stunting and premature death, malformations and overgrowth. Nematodes, or roundworms, are a large cause of disease in plants. They live in and cause damage to the roots, stems, leaves, and bulbs of plants.