During which period did the first fish evolve?

cambrian

ordovician

devonian

none of the above

How can antibodies "remember" a particular bacterial invader or "antigen" on that invader?

Do plant cells perform cellular respiration?

The hardy-weinberg principle is that genetic frequencies in a population? will remain stable from generation to generation will always be changing will not be affected by environmental changes are always in a 3: 1 ratio