Year 7 Science · Unit 1 · Lesson 05

Microorganisms

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Learning Goals

Trace how a virus infects a host cell and causes illness.
Sequence the steps by which yeast makes bread rise.
Apply knowledge of microorganism roles to explain real-world processes.

Warm Up

Because… chain

Fill in the missing effects. Each cause leads to the next step in how influenza virus causes illness. The shaded boxes are given; write the missing effects in the empty boxes.

Influenza virus enters the respiratory tract and reaches the airway cells

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The virus attaches to surface receptors on the host cell

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Viral DNA/RNA is copied using the host cell's machinery

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Hundreds of new virus particles assemble inside the host cell

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Overall outcome (illness or immune response):

Your Turn

Order the steps

Number the events from 1 to 6 to show the correct order of how yeast makes bread rise. Event 1 = what happens first.

Order	Event
	The heat of the oven kills the yeast cells.
	Yeast cells in the dough metabolise the sugars present in the flour.
	The dough has risen and is placed in a hot oven to bake.
	Carbon dioxide gas forms bubbles throughout the dough, causing it to expand.
	The baked loaf is light and airy because the gas bubbles are now set in the structure.
	Yeast releases CO₂ gas as a by-product of metabolising the sugar.

Show What You Know

1. A student says, "Viruses are just like bacteria — both cause disease the same way." Explain one key difference in how bacteria and viruses cause disease inside the human body.

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2. Fungi and bacteria are both decomposers. Explain why decomposers are essential for an ecosystem. What would happen to a forest if all decomposers disappeared?

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Wrap Up

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