Year 8 Science · Unit 1 · Lesson 21

Ecosystems, Biotic, Abiotic and Ecological Roles

Challenge Worksheet

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Date

Class

Learning Goals

Trace the cascade effects of a major abiotic change through an entire reef ecosystem
Apply knowledge of producers, consumers, and decomposers to a real environmental scenario
Evaluate the interconnectedness of ecological roles under climate change conditions

Go Deeper

What if…?

Scenario, Coral bleaching on the Great Barrier Reef

The Great Barrier Reef stretches over 2,300 km along Queensland's coastline and is the world's largest coral reef ecosystem. Coral polyps (the animals that build the reef) contain microscopic photosynthetic algae called zooxanthellae living inside their tissues. The zooxanthellae produce food for the coral through photosynthesis and give corals their colour. When ocean temperatures rise by even 1–2°C above normal for several weeks, as has happened repeatedly since the late 1990s due to climate change, corals expel their zooxanthellae in a process called coral bleaching. Without the algae, bleached corals turn white and cannot produce enough energy. If temperatures do not return to normal quickly, bleached corals die. Mass bleaching events in 2016, 2017, 2020 and 2022 have affected over 50% of the reef's corals.

Using your knowledge of producers, consumers, and decomposers, trace the cascade effect of mass coral bleaching through the entire Great Barrier Reef ecosystem. Your answer must address:
- what happens to producers (name zooxanthellae and coral in your answer)
- what happens to primary and secondary consumers (name at least two reef species)
- what happens to decomposers and nutrient cycling
- the overall effect on the abiotic factors of the reef environment

Challenge 6 marks

Go Deeper (continued)

Extension: The zooxanthellae are classified as producers. However, they live inside coral animal tissue. Does this change their ecological role? Explain your reasoning using the definition of a producer and the concept of interdependence.

Challenge 3 marks

Show What You Know

1. In the reef scenario, rising ocean temperature is an abiotic factor that triggers cascading effects on biotic factors. Explain why abiotic and biotic factors are described as "interconnected" rather than separate. Use the reef example in your answer.

Challenge 3 marks

2. Suggest one human action that could reduce the risk of further coral bleaching events. Explain the scientific mechanism by which this action would help, use at least one abiotic and one biotic factor in your explanation.

Challenge 3 marks

Wrap Up

In one sentence, what does the coral bleaching scenario reveal about the fragility of ecosystem interdependence?