Microorganism

Definition

Microorganisms are microscopic entities that can be bacteria, viruses, fungi, or protozoa. They are often unicellular and can only be seen with the aid of a microscope.

5 Must Know Facts For Your Next Test

1. Microorganisms were first observed by Antonie van Leeuwenhoek in the late 17th century using a simple microscope.
2. Louis Pasteur's experiments in the 19th century disproved spontaneous generation and proved that microorganisms cause fermentation and disease.
3. The Germ Theory of Disease, proposed by Robert Koch, states that specific diseases are caused by specific microorganisms.
4. Microorganisms play essential roles in various ecosystems, including nutrient cycling, decomposing organic matter, and as part of the human microbiota.
5. Some microorganisms are pathogenic and can cause diseases in humans, animals, and plants.

Review Questions

• Who first observed microorganisms under a microscope?
• What significant contribution did Louis Pasteur make to our understanding of microorganisms?
• What does the Germ Theory of Disease propose?

Related terms

Antonie van Leeuwenhoek: Dutch scientist known as 'the Father of Microbiology' who first observed microorganisms.

Louis Pasteur: French chemist who demonstrated the role of microorganisms in fermentation and disproved spontaneous generation.

Germ Theory of Disease: Theory proposing that specific diseases are caused by specific types of microorganisms.