Answer:
A feedback loop is a biological occurrence where the output of a system amplifies the system (positive feedback) or inhibits the system (negative feedback).
Explanation:
Example, during blood clotting, a cascade of enzymic proteins acitvates each other, leading to the formation of fibrin clot that prevents further blood loss.
Fixation
Nitrogen is converted from atmospheric nitrogen (N2) into usable forms, such as NO2-, in a process known as fixation. The majority of nitrogen is fixed by bacteria, most of which are symbiotic with plants. Recently fixed ammonia is then converted to biologically useful forms by specialized bacteria
That's how the food chain works. There isn't much to it.

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Energy flows from the first tropic level(the producers) to the consumers to decomposers then the cycle begins