What Is an Ecosystem?

An ecosystem is a community of living things (plants, animals, microorganisms) together with their non-living environment (water, soil, sunlight, air). Every organism in an ecosystem has a role to play, and they all depend on each other to survive.

Australia has many different ecosystems, including:

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Rainforest

Dense, wet forests like the Daintree in Queensland.

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Desert

Hot, dry areas like the Simpson Desert in central Australia.

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Coral Reef

Underwater ecosystems like the Great Barrier Reef.

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Bushland

Eucalyptus forests home to koalas, possums and birds.

Roles in an Ecosystem

Every organism in an ecosystem can be classified by how it gets its energy:

Producers

Organisms that make their own food using sunlight through photosynthesis.

Examples: Eucalyptus trees, grasses, seaweed, phytoplankton.

Producers are always at the start of a food chain.

Consumers

Organisms that eat other organisms for energy. There are different levels:

Primary (herbivores) -- eat plants (e.g. kangaroos, caterpillars)
Secondary (carnivores) -- eat herbivores (e.g. kookaburras)
Tertiary (top predators) -- eat other carnivores (e.g. wedge-tailed eagles)

Decomposers

Organisms that break down dead matter and return nutrients to the soil.

Examples: Fungi, bacteria, earthworms, millipedes.

Without decomposers, dead material would pile up and nutrients would not be recycled.

Food Chains and Food Webs

A food chain shows a single pathway of energy from one organism to the next. A food web is a network of interconnected food chains showing the many different feeding relationships in an ecosystem.

Australian Bushland Food Chain

Sun → Eucalyptus leaves → Koala → Wedge-tailed Eagle → Decomposers

The arrows show the direction that energy flows (from one organism to the next).

Important: If one species in a food web is removed, it affects many other species. For example, if insects disappear, the birds that eat them would have less food, and the plants that rely on insects for pollination would struggle to reproduce.

Key Vocabulary

Ecosystem

A community of living things interacting with each other and their non-living environment.

Producer

An organism that makes its own food from sunlight through photosynthesis (e.g. plants, algae).

Consumer

An organism that gets its energy by eating other organisms. Can be primary, secondary, or tertiary.

Decomposer

An organism that breaks down dead plants and animals, recycling nutrients back into the soil.

Worked Examples

1

In the food chain: Grass → Grasshopper → Frog → Snake, identify the producer and consumers.

Step 1: The producer makes its own food. Grass uses photosynthesis, so grass is the producer.

Step 2: The grasshopper eats the grass, so it is a primary consumer (herbivore).

Step 3: The frog eats the grasshopper, so it is a secondary consumer.

Answer: The snake eats the frog, so it is a tertiary consumer (top predator in this chain).

2

What would happen if all the frogs were removed from the food chain above?

Step 1: Without frogs, grasshoppers would have fewer predators and their population would increase.

Step 2: More grasshoppers would eat more grass, causing the grass population to decrease.

Answer: The snake population would decrease because they have lost a food source. The whole ecosystem becomes unbalanced.

3

Why are decomposers important to an ecosystem?

Step 1: When organisms die, decomposers like fungi and bacteria break down the dead material.

Step 2: This process releases nutrients back into the soil.

Answer: Decomposers are essential because they recycle nutrients so that producers (plants) can use them to grow, keeping the ecosystem running.

Knowledge Check

Select the correct answer for each question. Click "Check Answer" to see if you are right.

Question 1

In a food chain, which organism is always at the beginning?

A consumer A producer A decomposer A predator

Question 2

A kangaroo eats grass. What type of consumer is it?

Tertiary consumer Secondary consumer Primary consumer (herbivore) Decomposer

Question 3

What is the difference between a food chain and a food web?

They are exactly the same thing Food webs only exist in the ocean A food chain is bigger than a food web A food web is many interconnected food chains

Question 4

Which organisms break down dead material and recycle nutrients back into the soil?

Decomposers Primary consumers Producers Top predators

Question 5

In a food chain, the arrows show:

Which organism is bigger The direction energy flows Which organism moves faster The order they were discovered

Ecosystems & Food Webs