The ecosystem is able to support a large number of organisms due to the presence of plant producers that absorb light energy and converts it into chemical energy that is stored in carbohydrates during photosynthesis. Raw materials of photosynthesis include inorganic nutrients such as carbon dioxide and water.
Energy is then transferred to other organisms in the ecosystem through feeding relationships such as food chains and food webs.
In a food chain
producer --> primary consumer --> secondary consumer --> tertiary consumer
In any food chain, the producer will be the first organism that provides a source of energy to be transferred to different organisms in the food chain. The ultimate source of energy for food chain is from the sun.
During the transfer of energy from one organism (trophic level) to the next through the process of feeding, heat is also lost. Heat lost cannot be recycled. Therefore, transfer of energy is non-cyclical.
Inorganic nutrients such as carbon and nitrogen are obtained from the abiotic environment in the ecosystem and they flow through the ecosystem in a cycle. In a balanced ecosystem, nutrients are not lost as they are continually recycled through the action of decomposers, eg bacteria and fungi that break down the dead matter and excretory products such as faeces and return the nutrients to the ecosystem.
Food chains
A food chain refers to a series of organisms through which energy is transferred in the form of food. Each food chain always begin with a producer (ie plant or tree).
Each organism in a food chain feeds on the organism before it and provides food for the organism after it.
Consider the following food chain
potato plant à rat à snake à eagle
Potato plant is eaten by rat. Rat is eaten by snake. Snake is in turn eaten by the eagle. Each stage in a food chain is known as a trophic level. A trophic level is the feeding position of an organism in a food chain. In the above food chain, there are four trophic levels.
Loss of energy from one trophic level to the next
From one trophic level to the other, only 10% of the energy is transferred to the next organism.
Most of the energy lost is mainly in the form of heat energy during respiration, egestion, excretion and uneaten body parts.
This causes the flow of energy through the food chain to be non-cyclic.
Greater efficiency in energy transfer occurs through short food chains.
A food web consists of interlinked food chains in a community.