what types of structures did these organisms build that scientists are studying today? How old are the oldest of these structures?

Vaccines are weakened forms of disease causing microorganisms, which are given to patients to prevent disease. after the vaccine is administered, the immune system responds by creating a(n) to recognize the a.) antibody, antibiotic b.) antigen, antibody c.)antibiotic, antibody d.)antibody, antigen

Read each description below and determine to which stage of sleep each pertains. then click and drag each box into the appropriate category below.

This is the nitrogenous base only found in rna