Concept of Ecosystem - Energy Flow in Ecosystem

All life on Earth depends on the sun as the ultimate source of energy. In any ecosystem, energy flows in one direction - from the sun to producers, and then progressively to consumers and decomposers. Unlike matter, which is recycled, energy is never recycled; it is progressively lost as heat at each step.

Think of it like a leaky pipeline: water (energy) enters at one end (the sun/producers) and flows forward, but loses pressure (energy) at every joint (trophic level). By the time it reaches the last joint, very little remains.

Solar Energy and PAR:

• Of the total incident solar radiation striking Earth's surface, less than 50% is Photosynthetically Active Radiation (PAR).
• Of this PAR, plants manage to fix only 2–10% through photosynthesis to sustain the living world.
• The rest is reflected, transmitted, or dissipated as heat.

Two types of food chains exist in ecosystems:

A food web is a more realistic representation of feeding relationships in an ecosystem. It is a network of interconnected food chains.

Properties of a food web:

• Provides stability to the ecosystem - if one pathway is disrupted, energy can flow through alternate chains
• A single organism can occupy more than one trophic level in a food web (e.g., a sparrow eating both seeds [T2] and insects [T3])
• Food web complexity correlates with ecosystem resilience

• Energy flow in an ecosystem is strictly unidirectional, moving from the sun through producers to consumers and decomposers.
• Unlike physical matter, energy within an ecosystem is never recycled and is progressively lost as heat at every trophic step.
• Less than 50% of incident solar radiation is Photosynthetically Active Radiation (PAR), and plants capture merely 2–10% of this PAR to sustain the living world.
• Grazing Food Chains (GFC) originate with living plants and dominate aquatic ecosystems, while Detritus Food Chains (DFC) originate with dead organic matter and dominate terrestrial ecosystems.
• Interconnected food chains create complex food webs that provide ecosystems with essential stability, resilience, and alternative energy pathways.
• Within a complex food web, a single organism possesses the ecological flexibility to occupy more than one trophic level simultaneously.
• Organisms are structured into sequential trophic levels, from producers (T1) to apex predators (T4), with available energy drastically decreasing at each successive tier.
• Decomposers act systematically across all trophic levels to break down dead organic matter, forming a critical biological link for continuous nutrient recycling.