A pond's ecosystem food chain has three basic trophic levels. The first trophic level represents the producer and autotrophs, such as phytoplankton and plants. Producers prepare their own food with the energy emitted from the sun through a process known as photosynthesis. The second trophic level consists of herbivores, such as insects, crustaceans, and invertebrates that inhabit the pond and consume the plants. The third trophic level comprises of carnivores, such as various sizes of fish, which feed on both the plants and herbivores atop the first and second trophic levels. Saprotrophic organisms, also known as decomposers located on the bottom of the food chain, help decompose dead organic matter, which further breaks down into carbon dioxide and essential nutrients, such as nitrogen, phosphorus, and magnesium. These nutrients supply the necessary life force for the first trophic level organisms to produce food for the second trophic organisms, which results in the perpetual flow of energy in the pond's ecosystem.Bacteria and Fungi break down dead organisms into simpler substances and nutrients to be absorbed by the aquatic plants for surviva