. Principles of modern biology. Biology. 180 - The Cell A parasite may be neutral with reference to one kind of host, but definitely patho- genic to another. Such a case is provided by Cryptocotyle, a parasitic flatworm. The usual host of Cryptocotyle is a seagull, and adult gulls are quite immune to the presence of the parasite in their intestine. But mammals, such as the dog and fox, may become seri- ously ill when they are infected with Crypto- cotyle. Natural immunity depends to a large ex- tent upon the capacity of the host's tissues to form antibody substances (pp. 335 and 336). These an
. Principles of modern biology. Biology. 180 - The Cell A parasite may be neutral with reference to one kind of host, but definitely patho- genic to another. Such a case is provided by Cryptocotyle, a parasitic flatworm. The usual host of Cryptocotyle is a seagull, and adult gulls are quite immune to the presence of the parasite in their intestine. But mammals, such as the dog and fox, may become seri- ously ill when they are infected with Crypto- cotyle. Natural immunity depends to a large ex- tent upon the capacity of the host's tissues to form antibody substances (pp. 335 and 336). These antibodies counteract the toxic prod- ucts of the parasite; and the development of natural immunity indicates that an associa- tion between the parasite and host has ex- isted for a comparatively long evolutionary period. Nitrogen-fixing Bacteria. One case of sym- biosis deserves special emphasis, because it plays an important role in the conservation of soil fertility. The nitrogen-fixing bacteria live symbiotically in the root tissues of sev- eral common species of higher plants (Fig. 10-6). These bacteria are the only organisms that are able to utili/e free nitrogen (N5) in their metabolism. Such a usage involves. Fig. 10-6. Nitrogen-fixing bacteria. These symbiotic organisms live in the cytoplasm of cells of nodules found on the roots of clover and other leguminous Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Marsland, Douglas, 1899-. New York, Holt, Rinehart and Winston
Size: 1659px × 1506px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookcollectionbiodiversity, booksubjectbiology
