Year 7 Science · Unit 1 · Lesson 5

Microorganisms

Challenge Worksheet

Name

Date

Class

Learning Goals

Compare the four microbe groups and classify an unknown microbe from evidence.
Find and correct errors about microbes and disease.
Use data to evaluate a claim about antibiotics.

Warm Up

1. Complete the table to compare the four groups of microorganisms.

Recall 3 marks

Group	Made of cells? Nucleus?	How it feeds, or how it makes copies
Bacteria
Viruses
Fungi	Yes
Protists		Many eat other microbes; some photosynthesise

Your Turn

Find the error

A student wrote these five sentences for a health poster. Some are correct and some contain one error. Write “correct”, or rewrite the sentence so it is correct.

Recall 5 marks

#	Student’s sentence	Correct, or the fixed sentence
1	Tinea (athlete’s foot) is caused by a fungus infecting the skin.
2	Malaria is caused by Plasmodium, a bacterium spread by mosquitoes.
3	Chickenpox is caused by a virus, so a course of antibiotics will clear it up.
4	Salmonella is a bacterium that can cause food poisoning from undercooked chicken or eggs.
5	Mushrooms are plants, because they grow in soil and cannot move.

2. A microbiologist finds two new microbes. For each one, name its group and give two pieces of evidence from the description.
(a) Microbe X: a single cell with no nucleus, found in soil, killed by penicillin.
(b) Microbe Y: a single cell with a nucleus and chloroplasts, found swimming in pond water.

Apply 4 marks

Go Deeper

Read the data

Scenario: one week at a clinic

A doctor records every patient with an infection in one week, and what caused it. Only illnesses caused by bacteria can be treated with antibiotics.

Table 1. Patients with an infection in one week

Illness	Caused by	Number of patients
Common cold	a virus	38
Flu	influenza virus	22
Strep throat	Streptococcus (a bacterium)	9
Tinea	a fungus	6
Food poisoning	Salmonella (a bacterium)	5
Total		80

Source: made-up figures for this worksheet.

3. What percentage of the 80 patients had an illness caused by a virus? Show your working.

Apply 2 marks

Answer %

4. The doctor gives every patient in Table 1 a course of antibiotics. How many patients could the antibiotics help? Explain why they would do nothing for the tinea and flu patients, even though one is caused by a living cell and the other is not.

Analyse 3 marks

Show What You Know

5. Antibiotics are common, but medicines that stop viruses are much harder to invent. Use how a virus makes copies of itself to explain why.

Analyse 3 marks

Someone claims…

“Antibiotics are the best way to treat any infection. They kill bacteria AND viruses, so doctors should prescribe them for the flu, colds and bacterial infections equally. If you’re sick, always ask your doctor for antibiotics to get better faster.”

6. Evaluate this claim. Say which part is supported by science, which parts are wrong and why, and what evidence a doctor needs before prescribing antibiotics. Use Table 1 in your answer.

Analyse 6 marks

Answer Key (for teachers)

Question 1

Cells: bacteria yes, no nucleus; viruses no; protists yes, with a nucleus. Feeding: bacteria break food down outside the cell and absorb it; viruses hijack a host cell to build copies; fungi digest food outside the body and absorb it. Pathogens: Salmonella (food poisoning); influenza (flu); tinea fungus (athlete’s foot); Plasmodium (malaria); or other correct pairs. [3 marks: 1 per column]

Find the error

1 correct. 2 Plasmodium is a protist (it has a nucleus), not a bacterium. 3 Antibiotics do not work on viruses; chickenpox is not cleared by antibiotics. 4 correct. 5 Mushrooms are fungi, not plants: they absorb food and cannot photosynthesise. [5 marks]

Question 2

(a) Bacterium (1): one cell, no nucleus; killed by penicillin (1). (b) Protist (1): one cell with a nucleus; chloroplasts, pond water, like Euglena (1). [4 marks]

Question 3

38 + 22 = 60 (1); 60 ÷ 80 × 100 = 75% (1). [2 marks]

Question 4

9 + 5 = 14 (1). Flu: a virus is not a cell, so there is nothing to attack (1). Tinea: a fungus’s cell wall is made of chitin, not the bacterial wall that penicillin stops being built, so the antibiotic has nothing to attack (1). [3 marks]

Question 5

A virus copies itself with the host cell’s machinery (1); a drug that wrecked it would damage our own cells (1); a virus has no part of its own like a bacterial cell wall to target (1). [3 marks]

Question 6

Marking guide: 1 true part (antibiotics treat bacterial infections, e.g. strep throat); 1 they attack a bacterial structure (penicillin, cell wall); 1 viruses are not cells, so no effect on flu or colds; 1 data (75% viral); 1 harm (resistant bacteria); 1 doctor must first find whether a bacterium is the cause. [6 marks]

Model answer: Partly right: antibiotics treat strep throat because penicillin stops bacteria building cell walls. Viruses are not cells, so antibiotics do nothing for flu or colds, 75% of the clinic’s cases, and misuse breeds resistant bacteria. A doctor should first find out whether a bacterium is the cause.

Common error: calling Plasmodium a bacterium or a virus; it is a protist.