Ecosystems & Food Chains
Explore how living things depend on each other and their environment to survive.
What is an Ecosystem?
An ecosystem is a community of living things (plants, animals, fungi, bacteria) and non-living things (water, sunlight, air, soil, rocks) that all interact with each other in a particular place.
Think of a pond, a forest, a desert, or even a rotting log -- each one is an ecosystem! Everything in an ecosystem is connected.
Parts of an Ecosystem
Living Things (Biotic)
- ● Plants and trees
- ● Animals and insects
- ● Fungi and mushrooms
- ● Bacteria (tiny living things)
Non-Living Things (Abiotic)
- ● Sunlight
- ● Water and rain
- ● Air and wind
- ● Soil and rocks
Inquiry Question: What would happen if we removed all the plants from an ecosystem? How would the animals be affected? Think about connections between living things.
Food Chains
A food chain shows how energy passes from one living thing to another through food. Every food chain starts with a producer (a plant) that gets its energy from the sun.
A Simple Food Chain
SUN
Energy source
GRASS
Producer
RABBIT
Primary consumer
FOX
Secondary consumer
DECOMPOSER
Breaks down
Producer
Makes its own food using sunlight (photosynthesis). Examples: grass, trees, algae.
Primary Consumer (Herbivore)
Eats plants. Examples: rabbit, grasshopper, koala, caterpillar.
Secondary Consumer (Carnivore/Omnivore)
Eats other animals. Examples: fox, eagle, dingo, frog.
Decomposer
Breaks down dead plants and animals, returning nutrients to the soil. Examples: fungi, bacteria, worms.
Australian Food Chain Example
EUCALYPTUS
Producer
KOALA
Primary consumer
DINGO
Secondary consumer
FUNGI
Decomposer
Remember: The arrows mean "is eaten by" or "gives energy to."
Key Vocabulary
Ecosystem
A community of living and non-living things that interact in a particular environment.
Food Chain
A diagram showing how energy is passed from one organism to another through eating.
Producer
An organism (usually a plant) that makes its own food from sunlight.
Consumer
An organism that gets energy by eating other organisms.
Herbivore
An animal that only eats plants.
Decomposer
An organism that breaks down dead matter, returning nutrients to the soil.
Worked Examples
Build a food chain from these organisms: Eagle, Grass, Grasshopper, Frog
Step 1: Find the producer (the plant). Grass is the producer.
Step 2: What eats the grass? The Grasshopper eats grass (primary consumer).
Step 3: What eats the grasshopper? The Frog eats grasshoppers (secondary consumer).
Step 4: What eats the frog? The Eagle eats frogs (tertiary consumer).
Answer: Grass → Grasshopper → Frog → Eagle
What would happen if all the rabbits disappeared from a grassland ecosystem?
Step 1: Think about what eats rabbits. Foxes would have less food, so their numbers would drop.
Step 2: Think about what rabbits eat. Without rabbits eating the grass, grass would grow more.
Answer: Removing one part of a food chain affects the whole ecosystem. Fox numbers decrease and grass increases.
Is a rock a living or non-living part of an ecosystem?
Step 1: Does it grow, breathe, eat, or reproduce? No -- a rock does none of these things.
Step 2: But does it play a role? Yes -- rocks provide shelter and affect soil.
Answer: A rock is a non-living (abiotic) part of an ecosystem, but it is still important.
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 the producer?
Question 2
In the food chain: Eucalyptus → Koala → Dingo, what role does the koala play?
Question 3
Which of these is a non-living part of an ecosystem?
Question 4
What is the role of a decomposer in a food chain?
Question 5
Put this food chain in the correct order: Frog, Grass, Snake, Grasshopper
Key Concepts Summary
- ●An ecosystem includes all living (biotic) and non-living (abiotic) things interacting together.
- ●A food chain shows how energy flows from the sun to producers, to consumers, to decomposers.
- ●Producers (plants) make their own food; consumers eat other organisms.
- ●Decomposers break down dead matter and recycle nutrients back into the ecosystem.
- ●Removing one organism from a food chain affects the whole ecosystem.