These primary producers (autotrophs) are the food source which is then fed upon by primary consumers (heterotrophs) which are then fed upon by secondary consumers and so on up the food chain.
(These primary producers; are; the food source which is then fed upon by primary consumers (heterotrophs)) (the food source; is fed; upon; by primary consumers; T:then) (heterotrophs; are fed; by secondary consumers; T:then)
These primary producers the food source heterotrophs
are is fed are fed
the food source which is then fed upon by primary consumers (heterotrophs)
upon by primary consumers T:then
by secondary consumers T:then