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Chapter 17: Organizing Life’s Diversity. Honors Biology Mrs. Toner. Section 17.1 – The History of Classification. 1. How is classification used every day? 2. Why do scientists organize or classify living things? 3. Do you know the scientific names of any species?

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Section 17 1 the history of classification
Section 17.1 – The History of Classification

1. How is classification used every day?

2. Why do scientists organize or classify living things?

3. Do you know the scientific names of any species?

  • Biologists use a system of classification to organize information about the diversity of living things.

  • Just as stores group CDs according to type of music and artist, biologists group living things by their characteristics and evolutionary relationships.

Early systems of classification
Early Systems of Classification

  • Classification – is the grouping of objects or organisms based on a set of criteria.

  • Biologists find it easier to communicate and retain information about organisms when the organisms are organized into groups.

  • One of the principal tools

    for this is biological


Early systems of classification cont
Early Systems of Classification (cont.)

  • Aristotle’s System

    • Greek philosopher , Aristotle (394-322 B.C.)

    • Developed the first widely accepted system.

    • Classified organisms as either plants or animals.

See page 484

Table 17.1

Aristotle’s Classification System

Early systems of classification cont1
Early Systems of Classification (cont.)

  • Limitations of Aristotle’s System:

    • Viewed systems as being distinct, separate, and unchanging.

    • This was a common view until Darwin presented his theory of evolution which stated that organisms are always changing. Organisms share evolutionary relationships.

    • Nevertheless, many centuries passed before Aristotle’s System was replaced by a new one that was better suited to the increased knowledge of the natural world.

Early systems of classification cont2
Early Systems of Classification (cont.)

  • Linnaeus’s System:

    • Linnaeus (Swedish Naturalist, 1707-1778)

    • Broadened Aristotle’s classification method

    • Concentrated on morphology and behavior of organisms

    • Categorized birds into three major groups (see page 485, Figure 17.1)

    • Linnaeus’s system of classification was the first formal system of taxonomic organization.

    • Taxonomy – is a discipline of biology primarily concerned with identifying, naming, and classifying species based on natural relationships.

Early systems of classification cont3
Early Systems of Classification (cont.)

  • Linnaeus’s method of naming organisms called binomial nomenclature – gives each species a two-part name: genus and species

  • Latin

  • Cardinaliscardinalis

Taxonomic categories
Taxonomic Categories

(Created by Linnaeus)

  • Species and Genus

    • Taxon – a named group of organisms (plural, taxa).

      • Range from having broad diagnostic characteristics to having specific characteristics.

    • Think of taxa as a set of nesting boxes – one fitting inside the other. (See page 488, Fig. 17.4)

    • Domain

    • Kingdom

    • Phylum

    • Class

    • Order

    • Family

    • Genus

    • Species

The taxonomic categories
The Taxonomic Categories

  • Species – a group of organisms that can interbreed and produce offspring. [Ursusamericanus (American black bear), Ursusthibetanus (Asiatic black bear)]

  • Genus – (pl. genera) a group of species that are closely related and share a common ancestor. (Ursus = black bear)

  • Family – is the next higher taxon, consisting of similar, related genera. (Ursidae = all bears, both living and extinct; brown bears, polar bears, giant pandas)

    • All members of the bear family share certain characteristics. They walk flatfooted, have forearms that can rotate to clasp prey.

The taxonomic categories cont
The Taxonomic Categories (cont.)

  • Order – contains related families

  • Class – contains related orders

  • Phylum – (pl. phyla) or division (bacteria and plants) contains related classes

  • Kingdom - the taxon composed of related phyla or divisions

  • Domain – the broadest of taxa.

  • ACTIVITY: Classify a giant panda, Ailuropodamelanoleuca, completely from domain to species level by referring to Figure 17.4.

Answer to activity
Answer to Activity:

  • Eukarya, Animalia, Chordata, Mammalia, Carnivora, Ursidae, Ailuropoda, melanoleuca

Section 17 2 modern classification
Section 17.2 - Modern Classification

  • Determining Species – the definition of species has “evolved” over the years.

    • Typological Species Concept

    • Biological Species Concept

    • Phylogenetic Species Concept

      • Phylogeny – the evolutionary history of a species.

      • Shows evidence of a pattern of ancestry and descent.


  • To classify a species, scientists often construct patterns of descent, or phylogenies, by using characters.

  • Characters – inherited features that vary among species. Characters can be:

    • Morphological - similarity in anatomy

      • Example – Darwin’s Finches

    • Biochemical (Molecular)- similarity of nucleic acids(DNA) and amino acids (proteins)

    • Developmental - similarity in developmental patterns

    • Behavioral – similarity in vocalization or mating behaviors


  • The evolutionary history of a species or group of related species.

  • Organizes organisms based on their history and relation to one another.

  • A phylogenetic tree (or evolutionary tree) is a graphical hypothesis of the proposed phylogeny.

    • A phylogenetic tree is often called a cladogram.

    • A cladogram is a branching diagram that represents the evolutionary history of a species.

    • Cladistics – a method that classifies organisms according to the order that they diverged from a common ancestor.