The 7th grade students sealed their ecosystems today. The goal is to have all the organisms that they included survive for 3 weeks without anything new being added or anything old being removed from the ecosystem. Organisms include succulents, aquatic plants and algae, snails, roly polies , insects and a minnow. They had to decide how much of each thing to put in so that there was enough food to last, enough plant matter to cycle the oxygen and carbon dioxide, but not so much that it used it up, enough bacteria (or other detrivores) to process the waste and so forth. They are very excited and will be recording what happens daily for the next three weeks.