Question

Why is seletive media useful?

Answer 1

Seletive media can be used to interfere the growth of some organisms while allowing the others to grow normally. ( most commonly using blood agar or Eosin Methylene Blue)
Which is very useful in the field of Biotechnology

Hope this helps

Answer 2

Selective media are used for the growth of only selected microorganisms. For example, if a microorganism is resistant to a certain antibiotic, such as ampicillin or tetracycline, then that antibiotic can be added to the medium in order to prevent other cells, which do not possess the resistance, from growing. Media lacking an amino acid such as proline in conjunction with E. coli unable to synthesize it were commonly used by geneticists before the emergence of genomics to map bacterial chromosomes.