Which of the following is not a fossil?

worm burrow tube from 400 million yeas ago

deer tracks left in wet mud this morning

marine shell that is 1 million years old

all of the above are fossils

Anita thinks that she has heterozygous alleles for red hair. if she is correct, which of these diagrams best illustrates anitas alleles pf red hair

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?

What is any method of measuring the age of an object or event in years, such as using atomic half-life?