According to the relevant knowledge of ecosystem, this paper tries to analyze and answer the following questions: the traditional agricultural structure of "mulberry, silkworm and fish" has developed

According to the relevant knowledge of ecosystem, this paper tries to analyze and answer the following questions: the traditional agricultural structure of "mulberry, silkworm and fish" has developed into "mulberry, silkworm, gas and fish" (1) In this ecosystem, silkworms and mulberry, silkworms eat mulberry to get nutrition and survive, so silkworms and mulberry are predatory.

(2) Saprophytic microorganisms can decompose animal carcasses, dead plants and other substances into water, carbon dioxide and nitrogen, and return to nature to participate in the circulation of substances. Without saprophytic microorganisms, substances cannot be recycled. Therefore, saprophytic microorganisms (or bacteria and fungi) are the main organisms that play a role in the production of biogas by using silkworm excrement, human and animal feces, straw, weeds, leaves and other substances.

(3) Solar energy is first converted into energy stored in organic matter through photosynthesis of green plants, and then gradually utilized by various herbivores, carnivores and saprophytes, and part of it is distributed in the biosphere in the form of heat energy, so solar energy is the ultimate energy for all living things on the earth. Therefore, the energy required for fish to carry out life activities ultimately comes from sunlight, which is transformed from mulberry trees (or green plants) in this ecosystem through photosynthesis.

So the answer is:

(1) predation;

(2) Microorganisms

(3) sunshine; Mulberry.