With which group of organisms does the food chain and the cycle of substances begin in any ecosystem? Why?

There are 3 types of food chains:

1) Pasture,

2) Detrital,

3) Parasitic (but in this case we do not consider it).

In any food chain, the first link is either an energy producer (plant) or ready-made organic matter (detritus), from which the next link will then receive energy.

The food chain cannot start with an organic consumer (consumer), because without a producer, he has nowhere to take energy to provide it with the next trophic levels.