Chapter Overview

Microorganisms, also called microbes, are organisms that require a microscope to be readily observed.
In terms of numbers and range of distribution, microbes are the dominant organisms on earth.
Major groups of microorganisms include bacteria, algae, protozoa, fungi, parasitic worms, and viruses.
Microbiology involves study in numerous areas involving cell structure, function, genetics, immunology, biochemistry, epidemiology, and ecology.
Microorganisms have developed complex interactions with other organisms and the environment.
Microorganisms are essential to the operation of the earth’s ecosystems, as photosynthesizers, decomposers, and recyclers.
Humans use the versatility of microbes to make improvements in industrial production, agriculture, medicine, and environmental protection.
The beneficial qualities of microbes are in contrast to the many infectious diseases they cause.
Microbiologists use the scientific method to develop theories and explanations for microbial phenomena.
The history of microbiology is marked by numerous significant discoveries and events in microscopy, culture techniques, and other methods of handling or controlling microbes.
Microorganisms are the oldest organisms, having evolved over the 4 billion years of earth’s history to the modern varieties we now observe.
Microbes are classified into groups according to evolutionary relationships, provided with standard scientific names, and identified by specific characteristics.
Microorganisms can be classified by means of general categories called domains and cell types (procaryotes and eucaryotes).

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