Compare a shark and a bony fish in regard to how they maintain buoyancy
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Both sharks and bony fish are negatively buoyant. In order to maintain somewhat neutral buoyancy sharks have evolved a very large liver that produces an oily material called squalene. Squalene is less dense than seawater and thus it makes the sharks slightly positively buoyant. In addition, the wing-like pectoral fins of sharks aid in maintaining the buoyancy of the shark when it is swimming. Bony fishes do not produce squalene, although a few produce other oily materials. Many bony fishes rely on a gas-filled swim bladder as their only means of maintaining buoyancy. As a result, bony fishes with swim bladders, unlike many sharks, do not have to swim in order to maintain a certain level.
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Differentiation of the pleomorphic strains of streptococci and the similar corynebacteria or lactobacilli can be best accomplished by:
a. examination of Gram stain of the colony. b. vancomycin-susceptibility testing. c. serologic testing. d. examination of the morphologic features after growth in thioglycollate broth.
Bacterial resistance to penicillin began to appear
a. several decades after its first use. b. 100 years after its first use. c. after the drug supply was largely from synthetic sources. d. during the AIDS outbreak in the 1980s. e. within a few years of its introduction into general use.
Countries engage in trade because
a. the exchange is mutually beneficial. b. governments force industries to exchange. c. international law dictates that exchange must take place. d. All of these.
Bacteria can act as probiotic agents, such as species of ________ added to yogurt, to help impart health effects to the intestinal tract.
What will be an ideal response?