For example, you might want a predator and a prey population, or antigen and antibody turtles, or hydrogen and oxygen atom turtles.
(you; might want; a predator and a prey population, or antigen and antibody turtles, or hydrogen and oxygen atom turtles)
you
might want
a predator and a prey population, or antigen and antibody turtles, or hydrogen and oxygen atom turtles