Honors Biology
Mrs. Toner
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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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.
 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
classification.
 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
 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.
 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.
 Linnaeus’s method of naming organisms called
binomial nomenclature – gives each species a twopart name: genus and species
 Latin
 Cardinalis cardinalis
 Species and Genus
(Created by
Linnaeus)
 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
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inside the other. (See page 488, Fig. 17.4)
Domain
Kingdom
Phylum
Class
Order
Family
Genus
Species
 Species – a group of organisms that can interbreed
and produce offspring. [Ursus americanus (American
black bear), Ursus thibetanus (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.
 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, Ailuropoda
melanoleuca, completely from domain to species level
by referring to Figure 17.4.
 Eukarya, Animalia, Chordata, Mammalia,
Carnivora, Ursidae, Ailuropoda,
melanoleuca
 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.
Clade
Node