Pathogens and Disease
Master Pathogens and Disease for GCSE Biology with this free worksheet and full mark scheme — Foundation and Higher exam-style questions with worked answers for AQA, Edexcel and OCR. Pathogens can be bacteria, viruses, fungi or protists, and may spread through the air, through water or by direct contact.
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These worksheets and mark schemes are original, written for Virtus Academy and checked against the current AQA, Edexcel and OCR specifications. Every worksheet comes with a full mark scheme.
Topic overview
Pathogens are microorganisms that cause infectious disease. They may be bacteria, viruses, protists or fungi, and they infect both plants and animals.
Bacteria and viruses reproduce rapidly inside the body but cause disease in different ways. Bacteria produce toxins that damage tissues and make us feel ill. Viruses live and reproduce inside cells, causing cell damage when they burst out.
Pathogens spread in three main ways: by air, in droplets breathed out; by direct contact, including touching contaminated surfaces or skin; and by water, in contaminated drinking or bathing water. Understanding the route of transmission is what allows spread to be prevented.
Revision notes
Types of pathogen
Bacteria are living cells that reproduce rapidly and produce toxins damaging tissues.
Viruses are not cells; they reproduce inside host cells and burst them open. Protists are single-celled organisms, often carried by a vector. Fungi cause diseases in plants and on skin.
How pathogens spread
By air: droplets released when coughing or sneezing are breathed in by others.
By direct contact: touching contaminated surfaces, skin contact, or sexual contact. By water: drinking or bathing in water containing the pathogen.
Preventing spread
Each route suggests a preventive measure: hygiene such as handwashing, isolating infected individuals, vaccination, and destroying vectors.
An exam answer should link the measure to the route — handwashing prevents spread by direct contact, for instance.
Key points
- Pathogens are microorganisms that cause infectious disease.
- They include bacteria, viruses, protists and fungi.
- Bacteria produce toxins that damage tissues.
- Viruses reproduce inside cells and burst them.
- Pathogens spread by air, direct contact and water.
- Spread can be reduced by hygiene, isolation, vaccination and destroying vectors.
Worked examples
Example 1
State two ways in which pathogens can be spread. [2 marks]
Model answer
In the air, in droplets released when coughing or sneezing (1 mark). By direct contact, such as touching a contaminated surface (1 mark).
Example 2
Explain how bacteria and viruses differ in the way they make us feel ill. [2 marks]
Model answer
Bacteria reproduce rapidly and produce toxins that damage tissues (1 mark), whereas viruses reproduce inside body cells and cause damage when the cells burst open (1 mark).
Example 3
Explain how washing hands reduces the spread of disease. [2 marks]
Model answer
Washing hands removes pathogens from the skin (1 mark), so they are not transferred by direct contact to other people or to surfaces others will touch (1 mark).
Common mistakes
Calling all pathogens bacteria.
Viruses, protists and fungi are also pathogens.
Saying viruses produce toxins.
Bacteria produce toxins; viruses damage cells by reproducing inside them and bursting them.
Describing a preventive measure without linking it to a route.
Say handwashing prevents spread by direct contact.
Saying viruses are living cells.
They are not cells and can only reproduce inside a host cell.
Exam tips
- Learn the four types of pathogen and one disease for each.
- State the mechanism, not just that a pathogen makes you ill.
- Link every preventive measure to the route it blocks.
- Keep bacterial toxins and viral cell damage clearly distinct.
Key terms
- Pathogen
- A microorganism that causes infectious disease.
- Toxin
- A poison produced by bacteria that damages tissues.
- Vector
- An organism that carries a pathogen from one host to another.
- Communicable
- Able to be spread from one organism to another.
Related topics
Written and reviewed against the current AQA, Edexcel and OCR specifications. Spotted an error? Let us know.