Year 7 Science · Unit 1 · Lesson 17

Biodiversity

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Learning Goals

Apply the concept of genetic diversity to explain why low diversity makes populations vulnerable.
Predict and reason about the effects of biodiversity change on ecosystem resilience.
Use lesson concepts to evaluate a real-world conservation scenario.

Warm Up

Because… chain

Fill in the missing effects. Each cause leads to the next consequence in the chain. The given steps are shaded — fill in the blank steps.

A monoculture wheat farm has very low genetic diversity among the crop plants

→

A new fungal disease arrives and spreads rapidly through the genetically identical plants

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The food supply for people and animals that depend on wheat is severely reduced

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Species that depend on the wheat fields — insects, birds, small mammals — lose their food and shelter

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Overall outcome:

Your Turn

Predict + reason

Scenario

Conservationists in south-western WA are considering introducing a new controlled burn program across 200 hectares of kwongan heath. This ecosystem type has the highest plant species diversity per square metre of any ecosystem in Australia — some patches contain more plant species per square metre than a tropical rainforest. Many of these plants evolved to depend on fire for seed germination, but others are sensitive to burning.

(a) Predict two possible effects of the burns on biodiversity in the kwongan heath. Your predictions should address different levels of biodiversity.

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(b) Using the concepts of resilience and ecosystem services from the lesson, explain whether a controlled burn program is more likely to be beneficial or harmful to this ecosystem overall. Justify your reasoning.

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Show What You Know

1. The Cavendish banana — the variety sold in every Australian supermarket — is genetically almost identical across every plant grown worldwide. Using the lesson concept of genetic diversity, explain why this makes the global banana crop risky.

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2. Sydney's drinking water supply is protected by keeping the surrounding catchment forests intact rather than clearing them. Using the idea of ecosystem services, explain why clearing those forests would cost the city far more than it would save.

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Wrap Up

In one sentence, what was the main idea of this lesson?