Classification of Living Things
7 1 Classification
1.5 million different living things known
Thousands each year discovered
Taxonomy branch of biology
Naming living things
Early Classification Schemes
Two major groups
Plant kingdom and animal kingdom
Plants grasses, herbs, trees
Animals fish, creeping creatures, fowl, beasts, cattle
Fourth century B.C.
air-dwellers, land-dwellers, water-dwellers
mid-1600s John Ray
18,000 different types of plants and animals
Carolus Linnaeus founder of modern taxonomy
Linnaeus published his system of taxonomy in a book entitled Systema Naturae ( Classification of Nature ). Originally published in 1737, it went through 10 editions by 1758. His classification system allowed for the addition of new species. Also, because his classification system was easily adapted to the modern system of classification based on evolutionary relationships.
The modern classification system is analagous to the system for addressing mail. First, the country to which a letter is being sent must be identified; then, the correct state; then, the right city; then, the proper street; the, the family name; and finally, the first name of the individual to whom the letter is addressed.
Two word Latin name
The number of shared characteristics of each group becomes greater as one moves from phylum to species.
Classification categories are sometimes subdivided. For example a phylum may be divided into several subphyla. A single species may be divided into subspecies.
When naming a new species, taxonomists designate a single specimen of a species as the official standard for the species. This is called the type method.
The new definition of a species is applicable to organisms that reproduce sexually. For organisms that reproduce asexually, such as the ameba and paramecium, structural characteristics are used to distinguish between species.
Species natural group or population
Theory of evolution new species arise, or evolve, over long periods of time from preexisting species.
Phylogeny is the evolutionary history of a species or a group of organisms.
Information used to classify
Taxonomy in Perspective
Taxonomy is a dynamic and important field of biology.
Background: The rules governing the naming of organisms are provided in three publications:
The International Code of Botanical Nomenclature
The International Rules of Zoological Nomenclature
The International Bacteriological Code of Nomenclature
7.2 Major Taxonomic Groups
Early classification: two groups plants and animals
Six kingdom system ( figure 7-9, p.133 )
Archaebacteria ( Prokaryotic )
Eubacteria ( Prokaryotic )
Protista ( Eukaryotic )
Fungi are molds, yeast, mushrooms, rust, smuts
Plantae are mosses, liverworts, ferns, seed plants
Animalia are multicellular, organ or organ system level of organization
Biologists use a procedure
Taxonomic key is a tool used to identify organisms already classified by taxonomists.
Most keys are dichotomous.
Series of paired statements.
Each set of choices are arranged in such a way that each step produces a smaller grouping.
Evolution: A Unifying Theme
As a unifying theme in biology, evolution explains why there is such diversity of life on earth today as well as how various groups of organisms are related. It is also explains how the organisms of today are related to organisms of the past.
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