Some forests develop after farmland is abandoned. Grasses may be overtaken by pine trees which are eventually replaced by hardwood trees. During this process, the soil also changes. Which change during this process is a form of chemical weathering?

The following hormone had their receptors in the cell membrane except a-insulin b-tsh c-gh d- cortisol

Cells destroy body cells infected by a virus or bacteria.

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?