Answer:
As DNA contain phosphorus in its structure in large amount, therefore, Harshey and Chase labeled DNA with radioactive phosphorus and because protein contains some amino acids which have sulfur so they labeled T2 bacteriophage protein with sulfur.
So after that they infected E.coli bacteria with radioactively labeled phages and after centrifugation, they have found that pellet which contains cells is showing the presence of radioactive phosphorus and supernatant which have T2 phage capsid protein showing the presence of radioactive sulfur.
Therefore by labeling viral protein and viral DNA they found that DNA is the genetic material not protein.
Secondary succession because it was previously abandoned but since its been found theres a new ecosystem growing . ( u could word it a bit differently but it’s definitely secondary succession )
