Distinguish between the structure of pyrimidines and purines. explain why adenine bonds only to thymine.

The vaccine in a flu shot contains weakened flu viruses. how does a flu shot work with the immune system? a. it destroys lymphocytes. b. it destroys macrophages. c. it activates macrophages. d. it activates lymphocytes.

Which direction does the energy flow in this energy pyramid ?

What is the term for a water wave that is created by an underwater earthquake?