First, an ecosystem is a biological community of interacting organisms and their physical environment. Second biotic factors are nonliving things whereas biotic factors are living things in an ecosystem you have your producers or plants which then will be consumed by the primary consumers. With the primary consumers feeding the next group of consumers and then the next and then after they die they fertilize the ground allowing the producers to grow as it completes the circle of life.
Through the thin walls of the capillaries, oxygen and nutrients pass from blood into tissues, and waste products pass from tissues into blood. From the capillaries, blood passes into venules, then into veins to return to the heart.
