What is double circulatory system

Can someone me with this question/ give me the answer? you!

At the beginning of the virtual lab, you were asked to sort eight lizards into categories. what criteria did you initially use to make your groups? did you revise your criteria later? why?

As noted in the illustration, homo heidelbergensis was a tall, muscular hunter, who used both tools and weapons. because h. heidelbergensis was not a gatherer/forager, but ate a varied diet including meat and fish, we would expect to see what anatomical changes?