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Year 4 Science Biological Sciences

Food Webs

A food web shows how many food chains in an ecosystem are connected. Real ecosystems are much more complex than a single chain!

🔗 From Food Chain to Food Web

A food chain shows one path of energy — one animal eating another. But in real ecosystems, animals eat many different things, and many animals eat the same thing. When food chains overlap and connect, they form a food web.

🔗 Food Chain

One straight path of energy flow

Grass → Grasshopper → Frog → Snake → Eagle

Simple — one eating relationship

🌐 Food Web

Many food chains connected together

Grass → Grasshopper → Frog
Grass → Mouse → Snake
Frog + Snake → Eagle
Mouse → Eagle

Complex — many feeding relationships

Roles in a Food Web

🌿

Producers

Plants that make food from sunlight. They are the base of every food web. If producers disappear, the entire web collapses. Examples: grasses, trees, algae, seaweed.

🐇

Consumers

Animals that eat other living things. There are different levels: herbivores eat only plants; carnivores eat only animals; omnivores eat both plants and animals.

🍃

Decomposers

Organisms like fungi, bacteria, and worms that break down dead plants and animals. They return nutrients back to the soil, allowing producers to grow again. Decomposers complete the cycle!

An Australian Grassland Food Web

Here is an example of feeding relationships in an Australian grassland ecosystem:

Producers

Grass 🌿
Wattle 🌸
Seeds 🌻
↑ ↑ ↑

Primary Consumers (Herbivores)

Rabbit 🐰
Grasshopper 🐇
Parrot 🥣
↑ ↑ ↑

Secondary Consumers (Carnivores / Omnivores)

Snake 🐍
Lizard 🦜
Kookaburra 🐦

Top Predator

Wedge-tailed Eagle 🐦
↓ (when it dies)

Decomposers

Worms 🪲
Fungi 🍄
Bacteria

Worked Examples

Example 1: What would happen if rabbits disappeared?

If rabbits disappeared from the grassland food web, snakes and eagles would have less food, so their populations would decrease. But grass would not be eaten as much, so it would grow more. Other animals like grasshoppers might also increase.

✓ Removing one species in a food web affects the whole ecosystem.

Example 2: Why are decomposers important?

When a rabbit dies, worms and bacteria break down its body. This releases nutrients back into the soil, which helps grass and wattle to grow. Without decomposers, dead material would pile up and nutrients would be locked away forever.

✓ Decomposers recycle nutrients back into the ecosystem.

Example 3: Is a kookaburra a herbivore, carnivore, or omnivore?

A kookaburra eats insects, lizards, snakes, and small birds — it only eats animals. That makes it a carnivore and a predator in the food web.

✓ Kookaburras are carnivores — secondary consumers in the food web.

Key Vocabulary

Food Web

A diagram showing many interconnected food chains in an ecosystem.

Decomposer

An organism (like worms or fungi) that breaks down dead material and returns nutrients to the soil.

Ecosystem

A community of living things and their environment working together — for example, a forest, reef, or grassland.

Omnivore

An animal that eats both plants and animals. Example: humans, echidnas.

Knowledge Check

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Key Concepts Summary

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