Before 1970, the biological classification system was based on three kingdoms: Bacteria, Animalia, and Plantae. five kingdoms: Monera, Protista, Fungi, Animalia, and Plantae. two kingdoms: Monera and Animalia. two kingdoms: Animalia and Plantae. two kingdoms: Bacteria and Eukarya.

The hershey and chase experiments involved the preparation of two different types of radioactively labeled phage. which of the following best explains why two preparations were required? a. the bacteriophage used in the experiments was a t2 phage. b. it was necessary that each of the two phage components, dna and protein, be identifiable upon recovery at the end of the experiment. c. each scientist had his own method for labeling phage, so each conducted the same experiment using a different isotope. d. establishing the identity of the genetic material required observation of two phage generations.