Study Notes
Energy flow in ecosystems is primarily driven by sunlight, which is converted into chemical energy by photosynthesis. This energy flows through food chains, with energy being lost at each trophic level, ultimately as heat, which cannot be recycled.
- Sunlight — the primary energy source for most ecosystems.
Example: Plants use sunlight to perform photosynthesis. - Photosynthesis — process by which light energy is converted into chemical energy in carbon compounds.
Example: Phytoplankton convert CO2 into glucose using sunlight. - Food Chain — a sequence showing feeding relationships and energy flow between species.
Example: Grass → Grasshopper → Toad → Snake → Hawk. - Trophic Level — a position in a food chain occupied by a group of organisms with similar feeding mode.
Example: Producers, primary consumers, secondary consumers. - Respiration — process of releasing energy from carbon compounds, producing heat.
Example: Cells use ATP generated from respiration for metabolism. - Pyramid of Energy — a diagram showing energy flow from one trophic level to the next.
Example: Measured in kJ m–2 yr–1. - Biomass — total mass of a group of organisms, decreases along food chains.
Example: Higher biomass at producer level than at higher trophic levels.
Exam Tips
Key Definitions to Remember
- Sunlight
- Photosynthesis
- Food Chain
- Trophic Level
- Respiration
- Pyramid of Energy
- Biomass
Common Confusions
- Confusing food chains with food webs
- Misunderstanding that energy can be recycled like nutrients
Typical Exam Questions
- What is the primary source of energy for most ecosystems? Sunlight
- How is energy transferred through a food chain? Through feeding relationships
- Why can't heat energy be recycled in ecosystems? Heat energy is lost to the environment and cannot be converted back
What Examiners Usually Test
- Understanding of energy flow and loss in ecosystems
- Ability to describe and interpret food chains and pyramids of energy
- Knowledge of the role of photosynthesis and respiration in energy flow