Feeding relationships between organisms in a community are represented by food chains, which show the sequence in which organisms feed on each other. The chain generally begins with an autotroph such as a green plant (e.g. stinging nettle ---> small tortoiseshell butterfly caterpillar --> house sparrow --> sparrowhawk), or with dead organic matter (detritus) (e.g. leaf litter --> earthworm --> young blackbird --> fox). The arrows indicate the passage of food, and therefore energy flow, from one organism to another.
Pyramids of energy are the most accurate representation of feeding relationships in a community, providing information about the amount of energy flowing through each trophic level over a set period of time.
Food web involve many complex feeding relationship and most most ecosystems are more complex than food chain