BRAINCAKEProtozoa as Pathogens
Protozoa are single-celled eukaryotic organisms in the kingdom Protoctista. Unlike fungi and plants, they have no cell wall, and most are heterotrophic, feeding by engulfing food or absorbing nutrients. Many live freely in water or soil, but some are parasites that cause serious diseases in humans and animals.
Pathogenic protozoa often have complex life cycles with several different forms, which lets them survive in different environments and evade the immune system. Many are carried between hosts by a vector, an organism (usually an insect) that transmits a pathogen without being harmed by it. Others spread through contaminated food and water.
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Key terms in this lesson
- protoctista
- A kingdom of mostly single-celled or simple eukaryotic organisms, including protozoa and algae, that do not fit into the animal, plant or fungus kingdoms.
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All 17 lessons in Viruses, Fungi and Protozoa · All Edexcel A-level Biology topics