Food and energy pyramid

The food and energy pyramid shows the complex interdependence between plant and animal organisms in the ecosystem. The pyramid has several levels.

The primary producers (plants) are situated at the base of the pyramid -- the lowest and largest area -- known as the trophic level.

The organisms that consume plants are situated on the second level. These herbivores are also known as primary consumers.

Secondary consumers, feeding on animals (carnivores) or both plants and animals (omnivores), reside in the third and fourth levels of the pyramid.

Some consumers belong to more than one level. For example, man consumes plant and animal food from different levels of the pyramid.

Decomposers digest carcasses and the wastes of living organisms by breaking down the complex organic molecules in those materials into simpler inorganic compounds. Most of these chemicals return to the soil and water for reuse by producers.

Along with nutrients, energy is also transferred through the pyramid. The lines separating the different levels visually represent the transference of energy. The energy transferred from a lower to an upper level during consumption is approximately 10 percent.

For example, when primary consumers (from the second level) eat producers (first level), 100 kilograms of biomass is turned into 10 kilograms of biomass. When secondary consumers in turn eat primary consumers, this 10 kilograms of biomass becomes 1 kilogram.

Proponents of vegetarianism often use this logic to show how eating food from lower levels of the food and energy pyramid, or "eating closer to the Earth," actually conserves energy.

Everything that affects the lowest level also passes upwards in the system and affects the upper levels. Due to natural calamities (fires, floods, frost damage) or destructive human activity (deforestation, poisoning with chemicals, precipitation of toxic waste or any other sort of pollution), many vegetative areas are destroyed, which translates into less food for primary consumers. This leads to a food shortage for secondary consumers, and so on. Man is included in this chain and affected by all events occurring in the food and energy pyramid.

In the river valley 

In the forest 

In the meadow 

In the town