According to embryology, why do fish and birds have a common ancestor? they both have embryos with gill slits and tails. they both have embryos with traits that eventually disappear. they both have embryos that develop into adults. they both have embryos that form from a fertilized egg.

How many chromosomes are in a gold fish?

Use the drop down menus to match each example to the fossil topic discussed then to show how the fossil record gives evidence of evolution

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?