ANTIBIOTIC SUSCEPTIBILITY TESTING. Bacteria demonstrate two kinds of resistance to antibiotics, namely intrinsic resistance and acquired resistance. Intrinsic resistance means that the species was resistant to an antibiotic even before its introduction.
Radiation is naturally present in our environment, as it has been since before the birth of this planet. In addition, radiation can be produced artificially, as in medical x-rays and microwaves for cooking. Nonetheless, most people are not aware of all the natural and man-made sources of radiation in our environment.
1 Some energy is re-emitted back into the atmosphere, as longwave radiation. ' 2 Greenhouse' gases: carbon dioxide, nitrous oxide, methane, water vapour effectively prevent some of this longwave radiation from leaving the atmosphere. 3  This warms Earth's atmosphere, making our planet habitable.