Food Chain Worksheets - Free Printables - Free Printable

Let's solve the Food Chain Worksheet step by step, filling in the blanks and answering the questions based on ecological principles and the provided food web diagram.

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Part 1: Fill in the blank spaces

#### ①
> A food chain starts with a ________ and ends with a ________. Green plants are called ________ because they use the light energy of the sun to produce food using carbon dioxide and water through a process called ________. Animals cannot make their food and thus are called ________.

Answer:

- A food chain starts with a producer and ends with a decomposer.
- 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:
- Producers (like plants) make their own food via photosynthesis.
- Consumers rely on others for food.
- Decomposers (like fungi and bacteria) break down dead organisms and return nutrients to the soil.
- The food chain typically ends with decomposers, though sometimes it ends with top predators. But in ecological terms, the cycle completes with decomposition.

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#### ②
> There are ___ main trophic levels in a food chain. They are _______, _______, _______, _______, and _______. Apart from the said trophic levels, ________ have no natural predators except humans. Then, ________, like fungi and bacteria, turn dead ________ into inorganic materials in the soil.

Answer:

- There are five main trophic levels in a food chain. They are producers, primary consumers, secondary consumers, tertiary consumers, and quaternary 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 hierarchical levels in a food chain:
1. Producers (e.g., grass, trees)
2. Primary consumers (herbivores, e.g., rabbit, deer)
3. Secondary consumers (carnivores that eat herbivores, e.g., bird, snake)
4. Tertiary consumers (eat secondary consumers, e.g., hawk, mountain lion)
5. Quaternary consumers (top predators, e.g., mountain lion, hawk)
- Top predators (like mountain lion or hawk) usually have no natural predators.
- Decomposers recycle nutrients by breaking down dead organisms.

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Part 2: Use the food web diagram to answer the following questions

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

We need to trace the longest possible paths starting from a producer and ending at a top predator.

Let’s analyze the connections:

- Grass → Grasshopper → Shrew → Snake → Hawk
- Grass → Rabbit → Snake → Mountain Lion
- Tree → Deer → Mountain Lion
- Shrub → Rabbit → Bird → Hawk
- Grass → Squirrel → Snake → Hawk
- Grass → Grasshopper → Bird → Hawk
- Grass → Rabbit → Bird → Hawk
- Grass → Rabbit → Snake → Mountain Lion

Now, let’s identify the longest ones (most steps):

1. Grass → Grasshopper → Shrew → Snake → Hawk
*(5 steps: Producer → Primary → Secondary → Tertiary → Quaternary)*

2. Grass → Grasshopper → Bird → Hawk
*(4 steps)*

Wait — let’s check if there's a longer one.

But look:
- Grass → Grasshopper → Shrew → Snake → Hawk → 5 organisms
- Grass → Rabbit → Snake → Mountain Lion → 4 organisms
- Tree → Deer → Mountain Lion → 3 organisms
- Grass → Squirrel → Snake → Hawk → 4 organisms

So the longest food chain has 5 organisms.

Let’s find two such chains:

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

✔ Chain 2:
Grass → Grasshopper → Bird → Hawk → only 4 steps? Wait — is there another 5-step chain?

Check:
- Grass → Rabbit → Snake → Mountain Lion → 4 steps
- Grass → Grasshopper → Shrew → Snake → Hawk → 5 steps ✔
- Is there another 5-step chain?

Try:
- Grass → Rabbit → Bird → Hawk → 4 steps
- Grass → Squirrel → Snake → Hawk → 4 steps
- Grass → Grasshopper → Shrew → Snake → Hawk → 5 steps ✔
- Grass → Grasshopper → Bird → Hawk → 4 steps

Is Shrew eaten by Snake, and Snake by Hawk — yes.

Is Bird eaten by Hawk — yes.

But Grasshopper → Bird is direct? Yes, but then only 4 steps.

Wait — can we go:
Grass → Grasshopper → Shrew → Snake → Hawk → 5 steps ✔

Another possibility:
Grass → Rabbit → Snake → Hawk → 4 steps

No other organism eats Rabbit except Snake and Mountain Lion, but Snake → Hawk is valid.

What about Grass → Grasshopper → Bird → Hawk → 4 steps

Wait — what about Grass → Squirrel → Snake → Hawk → 4 steps

So only one chain has 5 links?

Wait — Grass → Grasshopper → Shrew → Snake → Hawk → 5 steps

Is there a second 5-step chain?

Check:
- Grass → Rabbit → Snake → Hawk → 4 steps
- Grass → Rabbit → Bird → Hawk → 4 steps
- Grass → Grasshopper → Bird → Hawk → 4 steps
- Grass → Squirrel → Snake → Hawk → 4 steps

But wait — Grass → Grasshopper → Shrew → Snake → Hawk is the only five-link chain.

Is there another?

What about Grass → Rabbit → Snake → Mountain Lion → 4 steps

Or Tree → Deer → Mountain Lion → 3 steps

No.

But what about Grass → Grasshopper → Shrew → Snake → Hawk — this is one.

Is Grass → Grasshopper → Bird → Hawk — 4 steps

Wait — is Grasshopper → Bird shown? Yes, arrow from Grasshopper to Bird.

But Bird → Hawk — yes.

But Grass → Grasshopper → Bird → Hawk — 4 steps.

No five-step chain involving Deer or Squirrel.

Wait — Grass → Rabbit → Snake → Hawk — 4 steps

But Grass → Grasshopper → Shrew → Snake → Hawk — 5 steps

Is there a second 5-step chain?

Let’s check Shrew:
- Eaten by Snake
- Snake eaten by Hawk and Mountain Lion

So:
- Grass → Grasshopper → Shrew → Snake → Hawk ✔
- Grass → Grasshopper → Shrew → Snake → Mountain Lion ✔

Yes! That’s a second one!

So both chains end with different apex predators.

So:

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

✔ Chain 2:
Grass → Grasshopper → Shrew → Snake → Mountain Lion

Both are 5 steps long — the longest possible.

Alternatively, could we have:

Grass → Rabbit → Snake → Mountain Lion → 4 steps

Still shorter.

So these two are the longest.

Also acceptable:
- Grass → Grasshopper → Bird → Hawk → 4 steps — not as long.

So the two longest are the two above.

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✔ Final Answers:

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Part 1: Fill in the blanks

(1)
A food chain starts with a producer and ends with a decomposer. 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 five main trophic levels in a food chain. They are producers, primary consumers, secondary consumers, tertiary consumers, and quaternary 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.

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Part 2: Food Web Questions

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

Answer:

1. Grass → Grasshopper → Shrew → Snake → Hawk
2. Grass → Grasshopper → Shrew → Snake → Mountain Lion

(Both are 5 trophic levels long — the longest in this food web.)

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✔ Note: The food web includes Fungi at the bottom, which are decomposers. They do not appear in food chains as consumers, but they complete the cycle by breaking down dead matter.

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