After exploring some of the ways that genomes change over evolutionary times, we highlight the handful of model organisms that biologists have chosen to focus on to dissect the molecular mechanisms underlying life. A few specific viruses, including SARS-CoV-2, pose grave threats to humans, so they too have become objects of intensive study. For this reason, this section also includes an introduction to viruses, the ubiquitous parasites that have evolved to feed on cells. Viruses are now recognized to be the most abundant biological entities on the planet.
–What is a Virus | Video by National Geographic
