Energy Flow
Principles of energy transfer in an ecosystem, encompassing food chains, food webs, trophic levels, and the 10% law.
What is Energy Flow?
Each step in a food chain or food web where energy is transferred from one organism to another.
Key formula / rule: 10% Law of Energy Transfer
Key points
- Explain the unidirectional flow of energy in an ecosystem.
- Describe the role of producers, consumers, and decomposers in energy transfer.
- Illustrate the concept of trophic levels.
- State and apply the 10% law of energy transfer.
Common exam trap
Confusing energy flow with nutrient cycling (which is cyclical).
Definitions
- Term
Trophic Level
- Meaning
Each step in a food chain or food web where energy is transferred from one organism to another.
- Term
Food Chain
- Meaning
A linear sequence of organisms where nutrients and energy are transferred as one organism eats another.
- Term
Food Web
- Meaning
A complex network of interconnected food chains showing multiple feeding relationships within an ecosystem.
- Term
Biomass
- Meaning
The total mass of organisms in a given area or volume, often used to represent energy at a trophic level.
Learning objectives
Explain the unidirectional flow of energy in an ecosystem.
Describe the role of producers, consumers, and decomposers in energy transfer.
Illustrate the concept of trophic levels.
State and apply the 10% law of energy transfer.
Differentiate between food chains and food webs.
Understand the implications of energy loss at each trophic level.
Formulae
- Name
10% Law of Energy Transfer
- Note
This is an approximation; actual transfer efficiency can vary.
- Expression
Energy at Trophic Level (n+1) ≈ 0.1 × Energy at Trophic Level (n)
Prerequisites
Photosynthesis
Basic understanding of biological organization (organisms, populations, communities)
Concept of producers, consumers, and decomposers
Common mistakes
Confusing energy flow with nutrient cycling (which is cyclical).
Assuming 100% energy transfer between trophic levels.
Incorrectly identifying trophic levels of organisms.
Overlooking the role of decomposers in energy flow.
Thinking energy can be recycled.
Keywords
Energy flow
Trophic level
Producers
Consumers
Decomposers
Food chain
Food web
10% law
Ecological efficiency
Biomass
Photosynthesis
Heat loss
Practice preview
According to the 10% law of energy transfer, if 10,000 kJ of energy is available at the producer level, how much energy will be available to the primary consumers?…
easy
A food web is a complex network of interconnected food chains. Which of the following best describes the primary function of a food web in an ecosystem?…
easy
In a typical grassland ecosystem, which trophic level would contain the largest amount of biomass?…
medium