Chapter Checkpoints
These are some important ideas you are learning in Chapter 1:

Introduction - The World of Microorganisms
There are many kinds of relationships between microorganisms and humans: mostly these are beneficial, but some are harmful.

In the last 110 years, microbiologists have identified the causative agents for most of the infectious diseases. In addition, they have discovered distinct connections between microorganisms and other diseases whose causes were previously unknown.

Microorganisms: We have to learn to live with them because we can't live without them

The Scope of Microbiology
Microorganisms are defined as ``living organisms too small to be seen with the naked eye'' with three exceptions: viruses, which are not really alive, but are microscopic, helminth worms, which are not always microscopic in size, and certain insects, which, although visible, carry microscopic agents of disease.

The scope of microbiology is incredibly diverse. It includes basic microbial research, research on infectious diseases, study of prevention and treatment of disease, environmental functions of microorganisms, and industrial use of microbiology for commercial, agricultural, and medical purposes.

The General Characteristics of Microorganisms
Excluding the viruses, there are two types of microorganisms: procaryotes, which are too small to have a nucleus and organelles, and eucaryotes, which have both a nucleus and organelles.

Viruses are not cellular and are therefore called particles rather than organisms. They are included in microbiology because of their small size and close relationship with cells.

Most microorganisms are measured in micrometers with two exceptions. The helminths are measured in millimeters and the viruses are measured in nanometers.

Contrary to popular belief, most microorganisms are harmless, fee-living species which perform vital functions in both the environment and larger organisms. Comparatively few species are agents of disease.

Historical Foundations of Microbiology
Our current understanding of microbiology is the cumulative work of thousands of microbiologists, many of whom literally gave their lives to advance knowledge in this field.

The microscope made it possible to see microorganisms and thus identify their widespread presence, particularly as agents of disease.

Anton van Leeuwenhoek is considered the father of bacteriology and protozoology because he was the first person to produce precise, correct descriptions of these organisms using microscopes he made himself.

The theory of spontaneous generation of living organisms form ``vital forces'' in the air was disproved once and for all by Louis Pasteur.

The scientific method is a process by which scientists seek to explain natural phenomena. It is characterized by specific procedures which either support or falsify an initial hypothesis.

Knowledge acquired through the scientific method is rigorously tested by repeated experiments by many scientists to verify its validity. A collection of valid hypotheses is called a theory. A theory supported by much data collected over time is called a law.

Scientific truth changes through time as new research brings new information. Scientists must be able and willing to change theory in response to new data.

Medical microbiologists developed the germ theory of disease and introduced the critically important concept of aseptic technique to control the spread of disease agents.

Koch's postulates are cornerstone of the germ theory of disease. They are still used today to pinpoint the causative agent of a specific disease.

Louis Pasteur and Robert Koch were the leading microbiologists during the Golden Age of Microbiology (1875?1900). Each had his own research institute.

Taxonomy - Organizing, Classifying, and Naming Microorganisms
Taxonomy is the formal filing system scientists use to classify living organisms. It puts every organism in its place and makes a place for every living organism.

The taxonomic system has three primary functions: classification, nomenclature, and identification of species.

The seven major taxa or groups in the taxonomic system are (in descending order): Kingdom, Phylum or Division, Class, Order, Family, Genus, and Species.

The binomial system of nomenclature describes each living organism by two names: genus and species.

Taxonomy groups organisms by phylogenetic similarity, which in turn is based on evolutionary similarities in morphology, physiology, and genetics.

Evolutionary patterns show a treelike branching from simple, primitive life forms to complex, advanced life forms.

The Whittaker five kingdom classification system places all bacteria in the Kingdom Procaryotae and subdivides the eucaryotes into Kingdom Protista, Mycetae, Animalia, and Plantae.

The Woese-Fox three kingdom classification system places all eucaryotes in the Domain (Superkingdom) Eukarya and subdivides the procaryotes into the two Domains Archaea and Bacteria.

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