Stromatolites are

a type of fossil dinosaur
produced by cyanobacteria
the earliest mammals
the earliest fossils
found as early as the archean era

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?

Wich level of organization includes all the other levels or organizations

Consider the venn diagram of plant reproduction. where in this image, areas a - d, would you insert the picture of the orange lily?