The eurasian water milfoil is a nonnative
species, which was once commonly sold as an
aquarium plant, and is now found growing in
many lakes in new york state. it has few
natural enemies, and grows rapidly, crowding
out many native species. this plant ruins fishing
areas and interferes with boating and other
water sports. this is an example of
(1) human consumption of finite resources
(2) an unintended consequence of adding an
organism to an ecosystem
(3) an abiotic factor having a negative effect on
an ecosystem
(4) the introduction of a species that has
increased the long-term biodiversity of an
ecosystem

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?

Give an example of a trait that is controlled by more than one gene.

To be or not to be that is da question