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Energy Flow
Energy Flow
The chemical energy of food is the main source of energy required by all living organisms. This energy is transmitted to different trophic levels along the food chain. This energy flow is based on two different laws of thermodynamics:
First law of thermodynamics, that states that energy can neither be created nor destroyed, it can only change from one form to another.
Second law of thermodynamics, that states that as energy is transferred more and more of it is wasted.
Energy Flow in Ecosystem
Energy Flow in Ecosystem
The energy flow in the ecosystem is one of the major factors that support the survival of such a great number of organisms. For almost all organisms on earth, the primary source of energy is solar energy. It is amusing to find that we receive less than 50 per cent of the sun’s effective radiation on earth. When we say effective radiation, we mean the radiation, which can be used by plants to carry out photosynthesis.
Only a fraction of the sun's energy, called Photosynthetically Active Radiation (PAR), reaches Earth, and plants use a small portion of that for photosynthesis. This energy, converted to chemical energy, flows through the food chain: producers (plants) are eaten by primary consumers (herbivores), then by secondary consumers (carnivores), and potentially tertiary consumers. At each level, energy is lost as heat, following the 10% rule where only 10% of energy is transferred to the next trophic level, creating a unidirectional flow represented by an energy pyramid.
Trophic Level
Trophic Level
The producers and consumers in the ecosystem can be arranged into different feeding groups and are known as trophic level or the feeding level.
The producers (plants) represent the first trophic level.
Herbivores (primary consumers) present the second trophic level.
Primary carnivores (secondary consumers) represent the third trophic level
Top carnivores (tertiary consumers) represent the last level.
Ecosystems feature three main food chain types: Grazing (GFC), where energy flows from plants to herbivores to carnivores; Detritus (DFC), starting with dead organic matter and decomposers; and Parasitic (PFC), where energy transfers from larger to smaller organisms. Due to omnivores feeding at multiple trophic levels, complex food webs are more commonly observed in nature than simple food chains.
G7–Q2: Lesson 5- Trophic levels and the transfer of energyPage updated
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