Which of the following is not a valid scientific method used by modern scientists to date fossils?
a use of index fossils
b relative position of fossils in rock strata
c analysis of nitrogen-14 isotopes
d analysis of uranium-238 isotopes

Keeping in mind the life cycle of bacteriophages, consider the following problem: during the reproductive cycle of a temperate bacteriophage, the viral dna inserts into the bacterial chromosome where the resultant prophage behaves much like a trojan horse. it can remain quiescent, or it can become lytic and initiate a burst of progeny viruses. several operons maintain the prophage state by interacting with a repressor that keeps the lytic cycle in check. insults (ultraviolet light, for example) to the bacterial cell lead to a partial breakdown of the repressor, which in turn causes the production of enzymes involved in the lytic cycle. as stated in this simple form, would you consider this system of regulation to be operating under positive or negative control?

Anne, an intern in a microbiology lab, was observing the characteristics of various specimens of protists. match each specimen to the category of protist to which it belongs.

In "the man in the water," what was the remarkable occurrence that rosenblatt reported?