Producers and feeding relationships explained
Ecology • Organisation of an ecosystem
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Key concepts
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Definition - Producer
A producer is an organism that photosynthesises and builds organic biomass from inorganic materials and sunlight. Plants and algae are photosynthetic producers and provide the primary source of biomass for almost all life on Earth, because they convert light energy into chemical energy stored in glucose .
Definition - Biomass
Biomass is the mass of living or recently dead organisms, usually measured as dried tissue to avoid variation from water content. Biomass represents stored chemical energy and material available to consumers at higher trophic levels .
Food chains and trophic levels
A food chain shows a linear feeding relationship from a producer to successive consumers using arrows that indicate the flow of energy or biomass. The first trophic level is almost always a photosynthesising producer; the next levels are primary, secondary, tertiary consumers and sometimes an apex predator at the top of the chain .
Energy transfer and limits to chain length
Producers capture only a small proportion of sunlight (about 1%) and convert it into biomass. At each trophic transfer, organisms use most energy for life processes so only about 10% of biomass or energy passes to the next level. Energy loss at each step causes food chains to be short, because insufficient energy remains to support many higher trophic levels .
Pyramids of biomass
A pyramid of biomass represents the total dry mass of organisms at each trophic level. Producers occupy the base with the largest biomass, and biomass decreases up the pyramid because energy and material are lost at each trophic transfer. Accurate biomass measurement usually requires drying samples to remove variable water content .
Key notes
Important points to keep in mind