Year 9 Science · Unit 1 · Lesson 5
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Learning Goals
Odd one out
Circle the item that does not belong in each group. Then explain why it doesn't fit.
| # | Group | Your answer (odd one + reason) |
|---|---|---|
| 1 | Virus Bacterium Fungus Cancer cell | |
| 2 | Droplets Direct contact Vector Keratinised skin | |
| 3 | Stomach acid Cilia Lysozyme Sebum | |
| 4 | Heart disease Asthma Influenza Type 2 diabetes |
Real-world context
Mycobacterium tuberculosis (Mtb) is the bacterium that causes tuberculosis (TB). In 2023, TB remained the second-leading infectious disease killer worldwide, according to the World Health Organization. Australia has a relatively low incidence of about 6 cases per 100,000 people per year, but rates are significantly higher in Papua New Guinea and parts of Western Sydney where overcrowding creates favourable transmission conditions. Mtb is spread by airborne droplets when an infected person coughs, speaks, or sneezes.
(a) Trace the complete journey of Mycobacterium tuberculosis from the moment an infected person coughs to the moment the bacterium successfully infects a new host's lung. At each stage, identify what first-line barrier it must overcome and how it overcomes that barrier.
(b) Explain why overcrowded living conditions increase the risk of tuberculosis transmission. Refer to a specific transmission route in your answer.
1. A person takes a broad-spectrum antibiotic for a bacterial skin infection, but later gets athlete's foot (a fungal infection). Explain why the antibiotic that cured the bacterial infection would be completely ineffective against athlete's foot, referring to the differences in structure between bacteria and fungi.
2. A person washes their hands with soap after gardening before eating lunch. Identify TWO different first-line defences that would protect them at the point where pathogens could enter the body during lunch.
Wrap Up
In one sentence, what was the main idea of this lesson?