Natural killer cells secrete ________, which forms pores in the membrane of infected or abnormal cells.
A) perforins
B) cytokines
C) pyrogens
D) C-reactive protein
E) interferon
Ans: A) perforins
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A key part of the humoral immune response is _____
A) the cytotoxic T-cell attack of infected host cells B) the production of antibodies by plasma cells C) perforation of infected host cells by perforin D) phagocytosis of pathogens E) the initiation of programmed cell death in infected host cells
The percent oxygen saturation of hemoglobin is highest in the:
a. tissues where oxygen concentration is lowest. b. tissues where oxygen concentration highest. c. venules where oxygen concentration lowest. d. pulmonary capillaries where oxygen concentration lowest. e. pulmonary capillaries where oxygen concentration highest.
Which one of the following is not an adaptation shown by modern birds?
A. a respiratory system that allows all of the air to pass through the lungs in one direction B. modified beaks and feet to support feeding behavior C. complete division of the heart into right and left halves D. endothermy E. wings and a long feathered tail
Biological magnification is best defined as ____
a. the increase in toxicity of a chemical compound resulting from its metabolism by a living organism b. the higher relative proportion of biomass among producers as compared to consumers in an ecosystem c. the concentration of nondegradable poisons within organisms at higher trophic levels d. the concentration of degradable poisons within organisms at lower trophic levels e. the declining relative proportion of nondegradable poisons in organisms at higher trophic levels as compared to those at lower trophic levels