Food Chain Worksheet featuring a food web diagram and questions about trophic levels and energy flow in ecosystems.

Here is the completed worksheet with explanations for each answer.

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① A food chain starts with a _producer_ and ends with a _top predator_. Green plants are called _producers_ because they use the light energy of the sun to produce food using carbon dioxide and water through a process called _photosynthesis_. Animals cannot make their food and thus are called _consumers_.

Explanation:
- Producer: Organisms (usually green plants) that create their own food using sunlight.
- Top predator: The animal at the very end of the food chain that has no natural predators (except humans).
- Photosynthesis: The biochemical process where plants convert sunlight, CO₂, and water into glucose (food) and oxygen.
- Consumers: Animals that must eat other organisms to get energy — they cannot produce their own food.

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② There are _four_ main trophic levels in a food chain. They are _producers_, _primary consumers_, _secondary consumers_, and _tertiary consumers_. Apart from the said trophic levels, _top predators_ have no natural predators except humans. Then, _decomposers_, like fungi and bacteria, turn dead _organisms_ into inorganic materials in the soil.

Explanation:
- Trophic levels are feeding positions in a food chain:
1. Producers – Plants (e.g., grass, shrubs, trees)
2. Primary consumers – Herbivores that eat producers (e.g., rabbit, deer, grasshopper)
3. Secondary consumers – Carnivores/omnivores that eat primary consumers (e.g., shrew, squirrel, bird)
4. Tertiary consumers – Top carnivores that eat secondary consumers (e.g., snake, hawk, mountain lion)
- Top predators – Like mountain lions or hawks — they sit at the top and are rarely preyed upon.
- Decomposers – Fungi and bacteria break down dead organic matter (dead animals/plants) into nutrients that enrich the soil, completing the cycle.

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Use the food web diagram below to answer the following questions.

① Write any two longest food chains in the food web.

✔ Food Chain 1:
Grass → Grasshopper → Shrew → Hawk

✔ Food Chain 2:
Tree → Deer → Mountain Lion

✔ *Bonus alternative (also 4 levels):*
Shrub → Rabbit → Snake → Hawk
or
Grass → Grasshopper → Bird → Hawk

Explanation:
To find the longest food chains, we count the number of steps (trophic levels) from producer to top predator.

Let’s trace some chains:

- Grass → Grasshopper → Shrew → Hawk = 4 levels ✔
- Tree → Deer → Mountain Lion = 3 levels (shorter)
- Shrub → Rabbit → Snake → Hawk = 4 levels ✔
- Grass → Grasshopper → Bird → Hawk = 4 levels ✔
- Tree → Squirrel → Hawk = 3 levels

So the longest chains have 4 links. Any two of the 4-level chains above are correct answers.

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✔ Final Answers Summary:

①
A food chain starts with a producer and ends with a top predator. Green plants are called producers because they use the light energy of the sun to produce food using carbon dioxide and water through a process called photosynthesis. Animals cannot make their food and thus are called consumers.

②
There are four main trophic levels in a food chain. They are producers, primary consumers, secondary consumers, and tertiary consumers. Apart from the said trophic levels, top predators have no natural predators except humans. Then, decomposers, like fungi and bacteria, turn dead organisms into inorganic materials in the soil.

① (Food Web)
Two longest food chains:
→ Grass → Grasshopper → Shrew → Hawk
→ Shrub → Rabbit → Snake → Hawk

*(Other valid 4-step chains also acceptable)*

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Let me know if you’d like a diagram drawn or more examples!