Types of Pathogens and How They Spread Revision Notes | GCSE OCR Foundation Biology

What this lesson covers

Learn about the four main types of pathogens (viruses, bacteria, protists and fungi) and understand how infectious diseases spread through direct contac...

• Explain what pathogens are and identify the four main types
• Describe how diseases caused by viruses, bacteria, protists and fungi spread in animals and plants
• Compare different methods of pathogen transmission including direct contact, water and air
• Apply knowledge of pathogen spread to suggest prevention methods

Key ideas to keep in view

Use this lesson to stay inside B6.3 Monitoring and maintaining health while connecting the detail back to the wider B6: Global challenges topic.

• B6: Global challenges
• B6.3 Monitoring and maintaining health
• GCSE OCR Foundation Biology

Lesson notes preview

Read the core explanations from Types of Pathogens and How They Spread before testing yourself from memory.

• Your body is under constant attack. Right now, millions of microscopic invaders are trying to get inside you, multiply, and make you ill. These disease-causing microorganisms have a name: pathogens.
• A microorganism that causes infectious disease. Pathogens may be viruses, bacteria, protists or fungi and can infect plants or animals.
• Think of pathogens as microscopic pirates. They board your body (the ship), steal your resources, and cause chaos. But not all microorganisms are pathogens — many bacteria in your gut actually help you digest food.
• Trap: Many students think all bacteria are harmful. Actually, most bacteria are harmless or even beneficial. Only pathogenic bacteria cause disease.
• Pathogens come in four main types, each with different characteristics and ways of causing disease. Picture them as different types of invaders, each with their own battle strategy.
• A non-living pathogen that can only reproduce inside host cells. Contains genetic material (DNA or RNA) surrounded by a protein coat.
• Viruses are like hijackers. They can't reproduce on their own, so they invade your cells and force them to make more viruses. Examples include influenza, COVID-19, and the common cold.
• Single-celled living organisms that can reproduce independently. Some are pathogenic and cause disease by producing toxins or damaging tissues.
• Pathogenic bacteria are like invading armies that set up camp in your body. They multiply rapidly and release poisonous toxins. Examples include Salmonella (food poisoning) and Streptococcus (sore throat).
• Single-celled organisms with a nucleus. Some are parasitic pathogens that live inside or on host organisms.

Continue through the topic

Move to the related lessons or back to the topic page when you need the wider sequence before exam-style practice.