There are only 20 amino acids used in all species on Earth with very little variation. What might scientists conclude from this?

Melting glaciers is a serious threat to the environment what is the possible consequence of melting glaciers on polar bears?

Are the earth's ocean floor and continents the same age geologically? why or why not?

Jason adds the antibiotic penicillin to a bacterial culture. the bacteria develop genetic modifications in their genome, which gives them resistance to the antibiotic penicillin. what caused this genetic modification?