What is the term used to denote the total rate of organic matter production during photosynthesis in an ecosystem?

Gross primary productivity

The correct answer is Option (4) -Gross primary productivity

Primary production refers to the amount of biomass or organic matter produced per unit area over a given time period by plants during photosynthesis. It is commonly measured in terms of weight (grams per square meter, gm^–2) or energy (kilocalories per square meter, kcal m^–2). Productivity, on the other hand, represents the rate of biomass production and is expressed as grams per square meter per year (g m^–2 yr^–1) or kilocalories per square meter per year (kcal m^–2 yr^–1) to facilitate comparison between different ecosystems.

Primary production can be further divided into two components: gross primary productivity (GPP) and net primary productivity (NPP). Gross primary productivity represents the total rate of organic matter production during photosynthesis in an ecosystem. However, a significant portion of this energy is utilized by plants for their own respiration needs.

Net primary productivity, on the other hand, is the amount of organic matter available for consumption by heterotrophs, such as herbivores and decomposers. It is calculated by subtracting the energy used by plants for respiration (R) from the gross primary productivity (GPP):

GPP - R = NPP.

Secondary productivity is defined as the rate at which new organic matter is formed by consumers in an ecosystem. It represents the energy flow and growth of heterotrophic organisms, including herbivores and decomposers, as they consume and process organic matter.

In summary, primary production is the biomass or organic matter produced by plants during photosynthesis, while productivity refers to the rate of biomass production. Gross primary productivity is the total rate of organic matter production during photosynthesis, and net primary productivity is the amount of organic matter available for consumption by heterotrophs after accounting for plant respiration. Secondary productivity is the rate of new organic matter formation by consumers.