Here is a video clip that reviews how evergy flows through an ecosystem and covers nutrient cycling.
Remember the following relationships:
Producers (Plants; Autotrophs)
Primary Consumers (Herbivores; Heterotrophs)
Secondary Consumers (Carnivores; Heterotrophs)
Tertiary Consumers (Carnivores; Heterotrophs)
Decomposers (Scavengers or Detritivores; Heterotrophs)
Keep in mind that energy flows ONE WAY through an ecosystem, while nutrients are RECYCLED.