EQ1: A system is basically where living things live together, helping and relying on each other most of the time. They all co-exist with each other. If one organism dies, the other organisms that needs this organism which died might not survive as this organism might just be the only organism an organism eats.
EQ2:Humans need food, water to survive. Thus, they look to the environment for these things. They could collect salt from the water, catch fishes or cockles etc. for food. The environment, likewise, also need us to survive as we have key points the environment do not have like science and technology.