Ampicillin is an antibiotic that kills bacterial cells by disrupting the formation of cell walls. However, the pARA-R plasmid has the ampicillin resistance gene, which produces a protein that breaks down ampicillin. What is the purpose of growing bacteria that have been transformed in the presence of ampicillin

To eliminate bacteria that failed to take in the plasmid.

Explanation:

Research shows that plasmid DNA is only taken in by small percentage of bacteria in a large population.

Therefore, the need of growing transformed bacteria in the presence of ampicillin is very important. The main reason of this process is to kill off or eliminate bacteria that have failed to take in the plasmid, due to their possession of recombinant DNA plasmid pARA-R (an ampicillin resistance gene), that allows them to survive.

However, after completion of the aforementioned procedure, the bacteria that have been transformed will be able to take in the plasmid.

This is to ensure  survival of desired bacterial cells.

Explanation:

The  growing of  transformed bacteria with ampicillin-resistant gene, ( in presence of ampicillin ) is for the ampicillin to disrupts the the process of synthesising protein  which inhibit its chemotherapeutic actions, therefore  promoting the survival of transformed  bacteria.

However, bacteria which are  without  plasmid,   which are not transformed,without the  ampicillin resistance gene, (since the action of ampicillin is not block,) will not be able to grow in the ampicillin medium,  and therefore  will be  killed.Thus aiding the survival of transformed bacteria only.

i think the miocene epoch spans the time from 23 million to 12 million years ago.