Energy Transfer in Trophic Chains and Food Webs

Energy Transfer in Trophic Chains

Photosynthetic organisms capture light energy from the sun that reaches the Earth's surface. These producers use this energy to perform photosynthesis, producing organic matter rich in energy from inorganic compounds.

Thus, light energy is converted into chemical energy and stored in the organic matter of the producers.

From One Link to the Next

What happens to the organic matter manufactured during photosynthesis?

• Respiration: A portion of the energy is degraded through respiration, used for the organism's vital functions, and released into the environment as heat.
• Waste: Parts of the organism, such as old leaves or roots, become waste and go directly to the decomposers.
• Stored Energy: The rest is stored in organs like leaves, roots, and fruits. This organic matter is what the next trophic level (herbivores) can consume.

The "Loss" of Energy

Energy adopts multiple forms and can transform from one to another, but it is never truly lost. When we turn on a lightbulb, electrical energy is transformed. Why is it often incorrectly called "lost energy"?

Herbivores cannot consume all the organic matter stored by producers. For example, many stems, roots, or fruit peels pass directly to the decomposers. Ultimately, only a portion of the organic matter stored by producers is converted into the biomass of herbivores.

Food Chains and Food Webs

Organisms in an ecosystem are linked by the "eat and be eaten" relationship. To represent these interactions, we use food chains or food webs, where organisms are joined by arrows meaning "is eaten by."

Trophic Levels

Food chains are a series of steps called trophic levels:

• Producers: Always belong to the first trophic level.
• Consumers: Occupy the subsequent levels. Some consumers can belong to several trophic levels depending on the chain.

A food chain consists of a linear series of organisms where each is eaten by the next highest level.

Trophic Webs

In an ecosystem, trophic relationships are rarely simple. Often, a herbivore feeds on different sources and is, in turn, eaten by various carnivores. For example, in a lagoon, algae are eaten by tadpoles, but water fleas also eat the algae and are consumed by dragonfly larvae.

These connections between different chains form a complex structure called a food web.