Ecosystems
Explore the interactions between living and non-living components of ecosystems, understand food webs and energy flow, and discover Australia's remarkable and unique biomes.
What is an Ecosystem?
An ecosystem is a community of living organisms interacting with each other and with their non-living environment. Ecosystems can be as large as the Great Barrier Reef or as small as a rock pool on an Australian beach.
Biotic Factors
The living components of an ecosystem.
- Plants (eucalyptus, wattle, mangroves)
- Animals (kangaroos, koalas, crocodiles)
- Fungi and bacteria (decomposers)
- Interactions (predation, competition, symbiosis)
Abiotic Factors
The non-living components of an ecosystem.
- Sunlight and temperature
- Rainfall and humidity
- Soil type and nutrients
- Wind, water currents, pH, salinity
Australian Curriculum Connection
This lesson aligns with AC9S7U01: "Interactions between organisms can be described in terms of food chains and food webs; human activity can affect interactions in ecosystems."
Food Chains and Food Webs
A food chain shows how energy passes from one organism to another through feeding. Arrows represent the direction of energy flow. A food web shows the complex network of food chains in an ecosystem.
Australian Savanna Food Web
Producers
Make their own food via photosynthesis (plants, algae). Form the base of all food chains.
Consumers
Obtain energy by eating other organisms. Herbivores (primary), carnivores (secondary/tertiary).
Decomposers
Break down dead organisms, returning nutrients to the soil. e.g. bacteria, fungi, worms.
Australian Biomes
Australia has a remarkable range of biomes — large regions defined by their climate and characteristic plants and animals. About 80% of Australian species are found nowhere else on Earth (endemic).
Desert / Arid (70% of Australia)
Very low rainfall (<250 mm/year). Spinifex grass, mulga, red kangaroos, thorny devil lizards, dingoes. Extreme temperatures.
Tropical Rainforest (Queensland)
High rainfall and temperature year-round. Massive biodiversity — cassowaries, tree kangaroos, hundreds of orchid species. Daintree is one of the oldest rainforests on Earth.
Temperate Eucalypt Forest
Eucalyptus (gum trees) dominate. Koalas, eastern grey kangaroos, wombats, lyrebirds, echidnas. Covers much of SE Australia.
Marine — Great Barrier Reef
World's largest coral reef system. Over 1,500 fish species, 4,000 mollusc species, sea turtles, dugongs, humpback whales. Threatened by warming and acidification.
Key Vocabulary
Biotic Factor
Any living component of an ecosystem, including all organisms and their interactions.
Abiotic Factor
Any non-living component of an ecosystem, such as temperature, water, sunlight, or soil type.
Food Web
A network of interconnected food chains showing the feeding relationships in an ecosystem.
Trophic Level
The position an organism occupies in a food chain; producers are level 1, primary consumers level 2, etc.
Worked Examples
Write a food chain for the Australian savanna ecosystem.
Identify: A producer, a primary consumer, and a secondary consumer.
Food chain:
Arrows show the direction of energy flow (from eaten to eater).
If a drought reduced the grass population, predict the effect on the food web.
Step 1: Less grass → primary consumers (grasshoppers, kangaroos) have less food → their populations decline.
Step 2: Fewer primary consumers → secondary consumers (lizards, eagles) have less prey → their populations also decline.
Conclusion: A reduction in producers causes a cascade effect through all trophic levels, reducing populations throughout the food web.
Give two biotic and two abiotic factors in the Great Barrier Reef ecosystem.
Biotic factors: Coral polyps (reef builders), clownfish, sea turtles, sharks, algae (zooxanthellae inside coral).
Abiotic factors: Water temperature, salinity, light intensity, ocean currents, pH/acidity, dissolved oxygen levels.
Two of each: Biotic — coral and clownfish. Abiotic — water temperature and salinity.
Knowledge Check
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Key Concepts Summary
- ✓ An ecosystem includes all living (biotic) and non-living (abiotic) components and their interactions.
- ✓ Food chains and food webs show the flow of energy from producers to consumers to decomposers.
- ✓ Arrows in food chains point in the direction of energy flow (from eaten to eater).
- ✓ Australia has unique biomes including deserts (70%), tropical rainforests, temperate forests, and the Great Barrier Reef.
- ✓ Changes in one part of a food web affect all other organisms — ecosystems are interconnected.