In aquatic systems no fish can survive in oxygen
concentrations below
a. 18 ppm
b. 4 ppm
c. 12 ppm
d. 14 ppm
e. none of these
Answer: b
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Scientists have found that the lifetimes of mRNAs coding for pair-rule regulatory elements in Drosophila embryos may last only a few minutes. What does this suggest about the overall developmental plan of an animal body?
A) The role of mRNAs is less important than the position of genes in chromosomes. B) Homeotic genes have greater impact in forming an embryo than mRNA from pair-rule genes. C) Building an animal body requires a sequence of precisely timed steps. D) Timing of pair-rule sequence determination is not as important as spatial signaling.
What is the name given to the chemicals which disrupt viral replication?
a. lymphokines b. monoclonal antibodies c. vaccine d. interferons e. complement
In three sentences or less, explain why a plant placed in a window grows toward the light. What will be an ideal response?
Nitrogen fixation is a process that
a) releases nitrate from the rock substrate. b) converts ammonia to nitrate. c) converts nitrogen gas into ammonia. d) recycles nitrogen compounds from dead and decaying materials. e) recycles nitrogen compounds from dead and decaying materials and converts nitrogen gas into ammonia.