Ecosystems

🔑 The one rule that unlocks the whole topic

Energy FLOWS one way; matter CYCLES around. Energy enters as sunlight, moves up the food chain, and leaves as heat — gone. Matter (carbon, water, nitrogen) is reused forever.

🏹 Food chain arrows

The arrow points in the direction the ENERGY moves — from the eaten to the eater. Grass → rabbit → fox means the rabbit gets energy FROM grass.

👥 Know your roles

• Producers (plants, algae): make food from sunlight — energy’s entry point.
• Consumers: herbivores eat plants, carnivores eat animals, omnivores eat both.
• Decomposers (bacteria, fungi): break down dead matter, returning nutrients to soil — the recyclers.

🎯 How the test will ask

• Expect a food web: “what happens if the ___ disappears?” Trace every arrow touching it, both directions.
• 10% rule math: 10,000 units in grass → 1,000 in rabbits → 100 in foxes. Practice dividing by 10.
• Cycle questions want the loop named step by step — where the carbon/water goes, in order.

✅ Before the test, can you…

• Sort ten things into biotic and abiotic?
• Draw a food chain with correct arrows?
• Apply the 10% rule to a 3-level pyramid?
• Explain why energy must keep entering but matter never runs out?
• Walk the water cycle and the carbon cycle out loud?