. Biology and man. Biology; Human beings. FORMER INHABITANTS Beavers, foxes, bears, minks, antelopes, moose and^ elk_are very rare turkeys, passenger pigeons, and heath hens are gone, with the buffaloes of the plains. Such bison herds as the one pictured above are protected in national parks abundantly as they have done under man's care and cultivation. These plants, as well as other species imported from various countries, have taken the place of dozens of species that might otherwise have thrived on this area under "natural" conditions. Transportation Man, moving with hi
. Biology and man. Biology; Human beings. FORMER INHABITANTS Beavers, foxes, bears, minks, antelopes, moose and^ elk_are very rare turkeys, passenger pigeons, and heath hens are gone, with the buffaloes of the plains. Such bison herds as the one pictured above are protected in national parks abundantly as they have done under man's care and cultivation. These plants, as well as other species imported from various countries, have taken the place of dozens of species that might otherwise have thrived on this area under "natural" conditions. Transportation Man, moving with his household effects and his cattle and his seeds for future planting, carries with him all the vermin, all the de- structive parasites of his household and his associates. Europeans traveling to the islands of the Indian and Pacific oceans brought with them infectious diseases that turned out to be very destructive to the natives. The whites, in turn, succumbed in large numbers to tropical diseases. Negroes brought as slaves to America in the eighteenth and nineteenth centuries carried with them an internal parasite, the hookworm, which they seemed able to tolerate without serious discomfort or privation (see page 615), Later, however, when this hookworm became established in the soil of our Southern states, the parasites infested large sections of the white population, with disastrous effects. Conversely, measles and other diseases long familiar to the white population attacked the Negroes with exceptional severity. From these examples we see that a parasite moving into a new region may find a host that is incapable of defending itself, and the parasite thrives. Or a species enters a new region and becomes the prey of parasites against which it has no defense. Or an invading species may be particularly destructive be- cause it finds suitable food but does not run into its old enemies. 588. Please note that these images are extracted from scanned page images that may have been
Size: 2453px × 1019px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., book, bookcentury1900, booksubjectbiology, booksubjecthumanbeings
