For two populations to evolve into two species that look different, what must happen
a. extinction
b. competition
c. continental drift
d. reproductive isolation

Why are scientists concerned about the depletion of the ozone levels in the stratosphere?

Pls me i need this ! each cell has genes activated depending on it's job and what kind of cell it is. it is the presence of that causes the repressor protein to fall off and unblock the gene on the lac operon. if a gene is turned on then it is being an additional circular chromosome found in some bacteria that is used in genetic engineering.

Can someone give me the answer to this question? you so much