What are protozoa?

Protozoa are microscopic single-celled organisms that usually live in water, moist soil, or inside the bodies of other organisms. They are animal-like microorganisms because many of them can move and feed on other organisms.

Some protozoa are harmless, while others cause diseases.

Characteristics of Protozoa

• Unicellular organisms

• Mostly microscopic

• Live in aquatic or moist environments

• Move using cilia, flagella, or pseudopodia

• Feed on organic matter or other microorganisms

Types of Movement in Protozoa

Structure Used	Example
Pseudopodia	Amoeba
Cilia	Paramecium
Flagella	Euglena

Examples of Protozoa

• Amoeba

• Paramecium

• Euglena

• Plasmodium

Useful Protozoa

Some protozoa help in:

• Maintaining ecological balance

• Controlling bacterial populations

• Nutrient recycling in aquatic ecosystems

Harmful Protozoa

Certain protozoa cause diseases in humans and animals.

Examples:

• Plasmodium causes malaria

• Entamoeba causes amoebic dysentery

Reproduction in Protozoa

Most protozoa reproduce through:

• Binary fission

• Multiple fission

Importance of Protozoa

Protozoa are important because they:

• Form part of aquatic food chains

• Help in decomposition and nutrient cycling

• Are studied in biology and medicine

Although some protozoa are disease-causing, many are beneficial for ecosystems.