These include bacteria, fungi, earthworms, cockroaches, crayfishes, etc. Primary consumers are eaten by secondary consumers etc. However, owls eat snakes and mice. People eat lettuce, yoghurt, ham sandwiches and eggs. In practice, reticulate interactions are more common.
Consumers get energy from primary producers.
Variations in the amount of solar energy reaching the earth's surface can limit the photosynthetic output of ecosystems in different locations. Only a small fraction of the solar energy reaches plants. Only some light is of wavelengths useful for photosynthesis. A part is lost because of cellular respiration of plants. The rest is excreted as frass.