This Power Point goes over the energy cycle in ecosystems. It defines producers, photosynthesis, consumers, decomposers, food webs, food chains. It also contains examples of those items to help the students comprehend the definitions. I have successfully used this from third grade students and even up to some post-secondary course.
This resource includes and explains the terms:
photosynthesis
producers
consumers
decomposers
herbivores
carnivores
omnivores
scavengers
food chain
food web
Both