Summary
Highlights
When energy is transferred from one trophic level to the next in an ecosystem, only about 10% of that energy is passed on. The remaining 90% is lost, primarily as heat. This rule explains how energy diminishes at higher trophic levels.
Organisms need food to survive. They can either make their own food (autotrophs) or eat other organisms (heterotrophs), forming food chains and food webs. Producers, like plants, are the initial energy source, creating their food through photosynthesis.
A food chain illustrates a single pathway of energy flow, from producers to the last consumers. It shows how energy is transferred when one organism eats another. For example, a plant (producer) is eaten by a grasshopper (primary consumer), which is then eaten by other consumers.
Using an example of 1 million joules of sunlight, producers harvest 10,000 joules. Primary consumers receive 1,000 joules (10% of 10,000), secondary consumers receive 100 joules, and tertiary consumers receive only 10 joules. This demonstrates the significant energy loss at each step.
In an ecosystem, food chains are not independent but overlap. A food web represents the natural interconnection of multiple food chains, showing more comprehensive feeding relationships and how different organisms interact within the ecosystem.
A food web example starts with berries (producers) eaten by a butterfly (primary consumer), which is then eaten by a frog (secondary consumer). The frog is eaten by a snake (tertiary consumer), which can then be eaten by another organism, illustrating the complex pathways of energy flow.