Relationships Of Organisms With One Another And With The Environment: Energy Flow
19.1 Energy Flow
Source Of Energy
- Sun = principal source of energy for life.
- Photosynthesis converts light energy → chemical energy in glucose.
- Almost all life depends on photosynthesis.
Flow Of Energy
- Energy passes along food chains/webs.
- Lost as heat, movement, respiration at each level.
- Only a small % transferred to next trophic level.
Key Terms
- Producer: Plant, makes food by photosynthesis.
- Consumer: Feeds on other organisms (herbivores, carnivores).
- Decomposer: Breaks down dead matter, recycles nutrients.
- Trophic level: Position of organism in a food chain.
Written And Compiled By Sir Hunain Zia, World Record Holder With 154 Total A Grades, 7 Distinctions And 11 World Records For Educate A Change O Level And IGCSE Biology Full Scale Course
Food Chains And Webs
- Food chain: Linear sequence (e.g., Grass → Grasshopper → Frog → Snake).
- Food web: Interconnected food chains, more realistic.
Pyramids
- Numbers: Show number of organisms.
- Biomass: Show mass of living material.
- Energy: Show energy content, always pyramid-shaped.
Why Chains Rarely >5 Levels
- Energy transfer inefficient (~10% passed on).
- Not enough energy to support many higher levels.
Humans And Energy
- More efficient to eat crops directly than to eat livestock fed on crops.
Written And Compiled By Sir Hunain Zia, World Record Holder With 154 Total A Grades, 7 Distinctions And 11 World Records For Educate A Change O Level And IGCSE Biology Full Scale Course