Productivity
Study of primary and secondary productivity, including Gross Primary Productivity (GPP) and Net Primary Productivity (NPP).
What is Productivity?
The rate at which producers convert light energy into chemical energy in the form of organic compounds.
Key formula / rule: Net Primary Productivity
Key points
- Define and differentiate between primary and secondary productivity.
- Explain the concepts of GPP and NPP.
- Identify factors influencing ecosystem productivity.
- Compare productivity across different ecosystems.
Common exam trap
Confusing GPP with NPP.
Definitions
- Term
Primary Productivity
- Meaning
The rate at which producers convert light energy into chemical energy in the form of organic compounds.
- Term
Gross Primary Productivity (GPP)
- Meaning
The total amount of energy captured by producers through photosynthesis per unit area per unit time.
- Term
Net Primary Productivity (NPP)
- Meaning
The amount of energy stored as biomass by producers after accounting for their own respiratory losses.
- Term
Secondary Productivity
- Meaning
The rate at which consumers accumulate biomass by ingesting organic matter.
Learning objectives
Define and differentiate between primary and secondary productivity.
Explain the concepts of GPP and NPP.
Identify factors influencing ecosystem productivity.
Compare productivity across different ecosystems.
Formulae
- Name
Net Primary Productivity
- Note
R represents the respiration rate of the producers.
- Expression
NPP = GPP - R
Prerequisites
Photosynthesis
Respiration
Trophic Levels
Biomass
Common mistakes
Confusing GPP with NPP.
Not accounting for respiration in productivity calculations.
Assuming all ecosystems have similar productivity rates.
Ignoring the role of decomposers in nutrient cycling which indirectly affects productivity.
Keywords
Productivity
Primary Productivity
Secondary Productivity
GPP
NPP
Photosynthesis
Respiration
Biomass
Ecosystem
Trophic Levels
Energy Flow
Practice preview
Which of the following ecosystems is likely to have the highest Net Primary Productivity (NPP)?…
medium
What is the primary source of energy for almost all ecosystems on Earth?…
easy
In a given ecosystem, the Gross Primary Productivity (GPP) is 1000 units and the respiration rate of producers is 200 units. What is the Net Primary Productivity (NPP) and the amount of energy available to herbivores?…
medium