Biology · Grades 9–12
Reasoning with food chains
Study guide for Grades 9 to 12: 2 worked examples and 2 practice questions. Arrows show the direction energy flows: from the organism eaten to the organism that eats it.
Rule and key idea
Arrows show the direction energy flows: from the organism eaten to the organism that eats it. In a simple chain, fewer prey usually means fewer predators, and fewer predators usually means more prey in the short term.
producer → primary → secondary → tertiary consumer
Worked examples
In this simplified food chain: grass → grasshopper → frog → snake → hawk. At which trophic level is “grass”? (Producers are level 1.)
Count from the producer: grass → grasshopper → frog → snake → hawk.
1
In this simplified food chain: phytoplankton → krill → baleen whale. What is the role of “phytoplankton” in this chain?
Level 1 in this chain: producer.
producer
Try two questions
In this simplified food chain: kelp → sea urchin → sea otter. At which trophic level is “kelp”? (Producers are level 1.)
In this simplified food chain: oak trees → caterpillar → songbird → hawk. What is the role of “caterpillar” in this chain?
- primary consumer
- tertiary consumer
- quaternary consumer
- producer
Answers and reasoning
Answers and marking notes
- 1
Count from the producer: kelp → sea urchin → sea otter.
- primary consumer
Level 2 in this chain: primary consumer.
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