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Gross primary production (GPP) is the amount of chemical energy, typically expressed as carbon biomass, that primary producers create in a given length of time.Some fraction of this fixed energy is used by primary producers for cellular respiration and maintenance of existing tissues (i.e., "growth respiration" and "maintenance respiration").
In small, forested streams, for example, the volume of higher levels is greater than could be supported by the local primary production. Energy usually enters ecosystems from the Sun. The primary producers at the base of the pyramid use solar radiation to power photosynthesis which produces food.
In trophic systems, photosynthetic organisms are the primary producers. The organisms that consume their tissues are called primary consumers or secondary producers—herbivores. Organisms which feed on microbes (bacteria and fungi) are termed microbivores. Animals that feed on primary consumers—carnivores—are secondary consumers. Each of ...
In contrast, terrestrial primary producers, such as forests, are K-strategists that grow and reproduce slowly, so a much larger mass is needed to achieve the same rate of primary production. Among the phytoplankton at the base of the marine food web are members from a phylum of bacteria called cyanobacteria.
Primary production is the synthesis of organic material from inorganic molecules. Primary production in most ecosystems is dominated by the process of photosynthesis, In which organisms synthesize organic molecules from sunlight, H 2 O, and CO 2. [3]
The organisms responsible for primary production are called primary producers or autotrophs. Most marine primary production is generated by a diverse collection of marine microorganisms called algae and cyanobacteria. Together these form the principal primary producers at the base of the ocean food chain and produce half of the world's oxygen ...
However, in aquatic ecosystems, primary producers are consumed by herbivores at a rate four times greater than in terrestrial ecosystems. [22] Although this topic is highly debated, researchers have attributed the distinction in herbivore control to several theories, including producer to consumer size ratios and herbivore selectivity.
Plants, along with other primary producers, produce the energy that other living beings consume, and the oxygen that they breathe. [3] It is thought that the first organisms on Earth were primary producers located on the ocean floor. [3] Autotrophs are fundamental to the food chains of all ecosystems in the world. They take energy from the ...