This is because in a food chain , energy flow from one trophic level to another. The producer which include plants are the source of energy which they manufacture good in the presence of light energy from sun. Energy flow directly from the producer to the primary consumer which are heterotrophs that feed on plants. Energy flow from consumer to decomposer after the consumer died and it is decayed.
I believe the answer is: Protons and Neutrons Protons weigh 1 amu while neutrons also weigh 1 amu. I’m not sure if they are talking about how many there is.
