Final answer:
Biomass is the term used to describe the total amount of organic matter in any level of a food web or ecosystem, which represents the mass of living or previously living organisms within a trophic level.
Step-by-step explanation:
The term used to describe the total amount of organic matter at any level of a food web or ecosystem is biomass. Biomass refers to the total mass, in a unit area at the time of measurement, of living or previously living organisms within a trophic level. Productivity within an ecosystem, on that note, can be defined as the percentage of energy entering the ecosystem that is incorporated into biomass in a particular trophic level.
Ecosystems have characteristic amounts of biomass at each trophic level which often decreases from lower trophic levels (producers) to higher ones (consumers and decomposers).
For example, a study in the English Channel ecosystem showed that primary producers account for a biomass of 4 g/m² (grams per square meter), while the primary consumers exhibit a biomass of 21 g/m². Understanding biomass is essential in ecology to grasp how matter and energy flow through ecosystems and the effects of human activities on ecosystem dynamics.