Lesson 4 of 12
🌿 Ecosystems & Food Webs
What You'll Learn
- Define ecosystem, producer, consumer, and decomposer
- Trace energy flow through a food chain and food web
- Understand the 10% energy rule
Ecosystem Roles
- 🌿 Producers (autotrophs) — make their own food via photosynthesis (plants, algae)
- 🦊 Primary consumers (herbivores) — eat producers (rabbits, deer, insects)
- 🦄 Secondary consumers (carnivores/omnivores) — eat primary consumers (foxes, frogs)
- 🦀 Tertiary consumers — eat secondary consumers (eagles, sharks)
- 🦠 Decomposers — break down dead organisms, recycling nutrients (bacteria, fungi)
The 10% Energy Rule
At each level of a food chain, only about 10% of the energy is passed to the next level. The rest is used for movement, heat, and body functions. This is why:
- Food chains rarely have more than 4–5 levels
- There are always far more plants than herbivores, and more herbivores than carnivores
- Eating lower on the food chain is more energy-efficient
🌿 Virtual Lab: Energy Pyramid
Enter the energy at the producer level (in kilocalories). See how much energy remains at each trophic level!
Producer energy (kcal):
Quick Check
If producers have 10,000 kcal of energy, how much reaches secondary consumers?
Decomposers are important because they: