Energy Flow Quiz

1. What is the principal source of energy for almost all biological systems?

• A. Chemical energy in soil
• B. The Sun
• C. Heat from the Earth's core
• D. Wind energy

2. What does a pyramid of energy show?

• A. The number of organisms at each trophic level
• B. The amount of energy present at each trophic level over a given time
• C. The total mass of all organisms in an ecosystem
• D. The types of species present in a habitat

3. Why is a pyramid of energy always pyramid-shaped, unlike a pyramid of numbers?

• A. Because energy is always lost at each trophic level, so it always decreases up the chain
• B. Because energy is created at each trophic level
• C. Because pyramids of numbers are always inaccurate
• D. Because energy pyramids ignore producers

4. A farmer could either grow wheat for direct human consumption or grow the same amount of wheat to feed cattle, which are then eaten by humans. Explain, in terms of energy flow, why growing wheat for direct consumption supports more people.

• A. Cattle produce more energy than they consume, so feeding cattle increases total available energy
• B. Energy is lost (as heat, waste and movement) when wheat is fed to cattle before reaching humans, so eating wheat directly makes more of the original energy available to humans
• C. Wheat contains no usable energy for humans
• D. Cattle convert 100% of the energy in wheat into meat

5. A food chain: grass → grasshopper → frog → snake → eagle. Using the concept of energy flow between trophic levels, explain why it would be very unlikely to find a sixth trophic level in this chain.

• A. There is a fixed law preventing more than five species from interacting
• B. So much energy is lost at each of the previous transfers that too little remains to support a viable population at a sixth trophic level
• C. Predators higher up the chain do not need any energy
• D. Grass produces a fixed, unlimited amount of energy regardless of chain length