Organisation of an ecosystem - EdexcelTransfer of biomass
The feeding relationships between organisms in an ecosystem can be seen in food chains. Sampling allows us to measure the abundance and distribution of these species.
The arrows in a food chainA sequence (usually shown as a diagram) of feeding relationships between organisms, showing which organisms eat what and the movement of energy through trophic levels. show the transfer of biomassThe dry mass of an organism. from one organism to another. An example of a food chain is:
maize → locust → lizard → snake
Some of the energy from the sun transferred by maize when it photosynthesisA chemical process used by plants to make glucose and oxygen from carbon dioxide and water, using light energy. Oxygen is produced as a by-product of photosynthesis. Algae subsumed within plants and some bacteria are also photosynthetic. is transferred to the locusts when they eat the plant. Then some of the biomass in the locust is transferred to the lizards when they are eaten and so on.
Energy available in the bodies of primary consumers
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Energy available in the bodies of secondary consumers
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Energy available in the bodies of tertiary consumers
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Slide1 of 4, Energy available in producers, Energy available in producers
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Not all of the biomass is passed from the maize plants to the locusts. In fact, only about 10% of the biomass is transferred from each trophic levelThe position of an organism in a food chain, food web or pyramid. to the next. The remaining 90% is used by the organism to complete life processesThe key reactions that all living organisms complete.. Biomass can be lost between stages because not all of the matter eaten by an organism is digested. Some of it is excreted as waste such as solid faecesWaste matter from the bowels., carbon dioxide and water in respirationThe chemical change that takes place inside living cells, which uses glucose and oxygen to release the energy that organisms need to live. Carbon dioxide is a by-product of respiration. and water and ureaA nitrogenous waste product resulting from the breakdown of proteins. It is excreted in urine. in urine.
Because only around 10% of the biomass at each trophic level is passed to the next, the total amount becomes very small after only a few levels. So food chains are rarely longer than six trophic levels.
In fact, only about 1% of the energy from the Sun that reaches the plant's leaves is used by the plant during photosynthesis. This sounds small but is still enough to power almost all food chains on the planet.