1. Which food-chain arrow direction is correct?
- Grass → rabbit
- Rabbit → grass for feeding
- Sun → fox as a feeding relationship
Check the answer and reasoning
Grass → rabbit
The arrow points from the food resource to its consumer.
Biology / Foundations
Organisms, resources and ecosystems
An ecosystem includes organisms and their physical environment.
Learning objectives
- Identify producers, consumers and decomposers.
- Trace a simple food chain.
- Distinguish energy transfer from nutrient cycling.
The big idea
An ecosystem includes organisms and their physical environment. Producers build organic material, consumers obtain it from other organisms and decomposers release nutrients from dead material and waste.
Food-chain arrows show the direction of energy transfer. Energy is dissipated during transfers and eventually leaves as heat; atoms can be recycled through organisms, soil, water and the atmosphere.
Worked example
A consumer receives 200 units from a producer containing 1000 units. Find transfer efficiency.
Follow the solution
Divide transferred energy by the starting amount: 200/1000×100=20%.
Investigate and explain
Using the worked example as supplied data, predict the effect of changing one condition. Draw a labelled model, record your reasoning and identify a variable that would need controlling. No human, animal or microbial experiment is required.
No exact PhET model is claimed for this topic. Use diagrams and supplied-data reasoning instead.
Check your understanding
2. A consumer receives 200 units from a producer containing 1000 units. Find transfer efficiency.
- 80%
- 20%
- 5%
Check the answer and reasoning
20%
Divide transferred energy by the starting amount: 200/1000×100=20%.
3. Is energy recycled in exactly the same way as mineral nutrients?
- Yes
- Only in forests
- No
Check the answer and reasoning
No
Nutrient atoms cycle; usable energy flows through a system and is dissipated as heat.