Edexcel iGCSE Biology-5.6 Trophic Levels- Study Notes- New Syllabus
Edexcel iGCSE Biology-5.6 Trophic Levels- Study Notes- New syllabus
Edexcel iGCSE Biology-5.6 Trophic Levels- Study Notes -Edexcel iGCSE Biology – per latest Syllabus.
Key Concepts:
5.6 understand the names given to different trophic levels, including producers, primary, secondary and tertiary consumers and decomposers
Trophic Levels in Food Chains
🔹 Introduction
Trophic level = position of an organism in a food chain, based on how it gets energy.
Energy in an ecosystem always flows in one direction:
☀️ Sun → 🌿 Producers → 🐇 Consumers → 🍄 Decomposers
Each step in a food chain = one trophic level.
📌 Main Trophic Levels
1. Producers (Autotrophs)
- Definition: Organisms that make their own food using sunlight (photosynthesis) or chemicals (chemosynthesis).
- Examples: Green plants, algae, phytoplankton.
- Role: Convert light energy into chemical energy (glucose). Basis of all food chains.
- Mnemonic: Producers = “Power Starters” of the chain.
2. Primary Consumers (Herbivores)
- Definition: Organisms that eat producers.
- Examples: Rabbit, cow, caterpillar, zooplankton.
- Role: Transfer energy from plants to higher levels.
- Note: Herbivores = second trophic level.
3. Secondary Consumers (Carnivores/Omnivores)
- Definition: Organisms that feed on primary consumers.
- Examples: Fox, frog, small fish.
- Role: Control herbivore population, maintain balance.
- Note: Omnivores (like humans, bears) may act as secondary consumers if they eat herbivores.
4. Tertiary Consumers (Top Carnivores)
- Definition: Carnivores that feed on secondary consumers.
- Examples: Lion, eagle, shark, tiger.
- Role: Top predators, regulate populations of lower consumers.
- Note: Occupy the highest trophic level (often 4th but can extend in long chains).
5. Decomposers
- Definition: Microorganisms that break down dead organisms and waste into nutrients.
- Examples: Bacteria, fungi, earthworms.
- Role: Recycle nutrients back to soil/water and make them available to producers again.
- Important: Not part of a single trophic level → work at all levels.
📊 Summary Table
| Trophic Level | Group | Food Source | Examples |
|---|---|---|---|
| 1st | Producers | Sunlight (photosynthesis) | Grass, algae |
| 2nd | Primary Consumers | Producers | Rabbit, cow |
| 3rd | Secondary Consumers | Primary consumers | Frog, fox, fish |
| 4th | Tertiary Consumers | Secondary consumers | Lion, eagle |
| – | Decomposers | Dead organisms/waste | Bacteria, fungi |
🌍 Energy Flow in a Simple Food Chain
Sun → Grass (Producer) → Rabbit (Primary) → Fox (Secondary) → Eagle (Tertiary) → Decomposer
At each step, energy is lost as heat, movement, and waste.
Only ~10% of energy is passed on to the next trophic level (10% law).
📝 Quick Recap
Producers = autotrophs, base of food chain.
Consumers: Primary = herbivores | Secondary = small carnivores/omnivores | Tertiary = top predators.
Decomposers recycle nutrients at all levels.
Energy flow = one-way, Sun → Producers → Consumers → Decomposers.
Rule: Only ~10% energy transfer between trophic levels.