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Bacteria, viruses and pathogen entry
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Exposure, infection and disease

Exposure, infection and disease

Flow diagram showing respiratory, digestive, skin and urogenital entry routes converging on entry, defence evasion, attachment, replication and disease

A pathogen is a biological agent that can cause disease. Exposure alone is not the same as infection, because infection begins only if the pathogen enters the body and multiplies.

Bacteria, viruses and pathogen entry Lesson

  1. A Level
  2. /Biology
  3. /Bacteria, viruses and pathogen entry

Step-by-step lessons on Edexcel A A Level Biology Bacteria, viruses and pathogen entry. Each one builds up to exam-style questions. Build a strong foundation in cell biology and biochemistry early on, since later topics on genetics, ecology and physiology all draw on these core concepts.

Lessons