Explain energy flow in ecosystem.

(N/A) Except for the deep sea hydro-thermal ecosystem,the sun is the only source of energy for all ecosystems on Earth.
Of the incident solar radiation,less than $50$ per cent is photosynthetically active radiation $(PAR)$. Plants,photosynthetic bacteria,and chemosynthetic bacteria (autotrophs) fix the sun's radiant energy to produce food from simple inorganic materials.
Plants capture only $2-10$ per cent of the $PAR$,and this small amount of energy sustains the entire living world.
All organisms are dependent on producers for their food,either directly or indirectly. Thus,the energy flow is from the sun to producers and then unidirectional to consumers.
Furthermore,ecosystems are not exempt from the second law of thermodynamics. They require a constant supply of energy to synthesize the molecules they need and to counteract the universal tendency toward increasing disorderliness.
In ecosystem terminology,green plants are called producers.
In a terrestrial ecosystem,major producers are herbaceous and woody plants. Similarly,primary producers in an aquatic ecosystem include various species like phytoplankton,algae,and higher plants.
Food chains and food webs exist in nature. Starting from the plants (or producers),food chains or webs are formed such that an animal feeds on a plant or another animal and,in turn,becomes food for another.
This interdependency forms the chain or web.
- No energy trapped in an organism remains in it forever. The energy trapped by the producer is either passed on to a consumer or the organism dies.
$\Rightarrow$ The death of an organism marks the beginning of the detritus food chain/web.
- All animals depend on plants (directly or indirectly) for their food needs. They are hence called consumers or heterotrophs.
- If they feed on producers (plants),they are called primary consumers. If they eat other animals that feed on plants,they are called secondary consumers. Similarly,tertiary consumers exist.
Primary consumers are herbivores. Common examples include insects,birds,and mammals in terrestrial ecosystems,and molluscs in aquatic ecosystems.
Consumers that feed on these herbivores are carnivores (specifically,primary carnivores).
- Animals that depend on primary carnivores for food are labeled as secondary carnivores.