An ecosystem is where there are various species and their interactions to the physical environment in which they live as well as to each other makes the ecosystem. In an ecosystem there are three orders of consumers which are:
First order consumer (They depend on the food producers i.e. those who produce their own food like plants etc. first order can be understood by the examples of mouse, caterpillar etc.).
Second order consumer (These depend and eat the first order consumer. The example for second order is snake etc.)
Third order consumer (Those dependent on second order like hawk etc.)