When a person eats, the brain signals the stomach to start breaking down the food. Which two 1 point systems are involved in this process?*
Circulatory and respiratory
Nervous and digestive
Digestive and excretory
Muscular and digestive

In trying to determine whether dna or protein is the genetic material, hershey and chase made use of which of the following facts? a) dna contains sulfur, whereas protein does not. b) dna contains phosphorus, whereas protein does not. c) dna contains nitrogen, whereas protein does not. d) dna contains purines, whereas protein includes pyrimidines.