By comparing fossils in higher sedimentary layers with fossils in lower sedimentary layers, scientists can learn which of the following?
which types of organisms were more common during various time periods
the relative age of different species
how species have evolved over time

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.