The organisms that start every food chain and end every food chain respectively are
producers and decomposers.
Producers, also known as autotrophs, are organisms that can produce their own food through photosynthesis or chemosynthesis. They are at the start of the food chain because they are able to convert energy from sunlight or chemical reactions into organic molecules that can be used by other organisms.
Decomposers, on the other hand, are organisms that break down dead organic matter into simpler substances. They are at the end of the food chain because they recycle nutrients back into the ecosystem, making them available for producers to use again. Examples of decomposers include fungi, bacteria, and some species of insects.