Because of the fossils found in these sedimentary layers, we could infer that A) Land plants are older than land animals. B) Vertebrates and invertebrates lived together. C) Invertebrates lived on Earth before vertebrates. D) Land animals lived on Earth before ocean dwellers.

Drag each label to the correct location on the table. each label can be used more than once. decide whether each statement describes saturated fat, unsaturated fat, or both saturated and unsaturated fats.

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?

Which of the following statements about archaea and bacteria is true? a. neither is single-celled. b. they both have nuclear membranes. c. neither reproduces by binary fission. d. they both lack a nuclear membrane.