While a backhoe operator is helping to clear land that will be used for a poultry farm, the equipment opens up a hidden chamber in which old electrical transformers have been buried. The operator knows that transformers contain PCBs
Why should this person warn the owners of the land?
PCBs can cause cancer and are nondegradable, posing a threat to workers at the poultry farm and to consumers of the chickens and eggs produced there.
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Which of the following correctly describes the fate of the embryonic germ layers?
A. The endoderm forms the gut, the ectoderm forms the epidermis and parts of the nervous system, and the mesoderm forms muscles and most internal organs. B. The endoderm forms the gut, the ectoderm forms the reproductive tract and endocrine system, and the mesoderm forms muscles and most internal organs. C. The endoderm forms the inner part of all internal organs, the mesoderm forms the middle parts, and the ectoderm forms the outer coverings. D. The layers are sequential structures that all disappear during development, with the endoderm appearing first and then is replaced by the mesoderm, which in turn is supplanted by the ectoderm. E. The endoderm is an embryonic structure that disappears early, whereas the ectoderm persists as the skin and the mesoderm as the internal organs.
Which of the following groups does NOT belong to the Alveolates?
a. apicomplexans b. diatoms c. dinoflagellates d. parasitic ciliates e. free-living ciliates
Dark Field Microscopy
A. uses light beams that are deflected by a different thickness of the object and are reflected when they strike the objective B. is used to observe viruses and the internal structure of thinly sectioned cells C. is used to observe a specimen that emits light when illuminated with an ultraviolet light D. is used primarily to view spirochetes
Only mammals and birds can produce urine that is
A. hypertonic. B. isotonic. C. hypotonic.