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Chapter 13
Lecture Outline
Plant Names and
Classification
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Outline

Introduction

Development of the Binomial System of
Nomenclature
• Linnaeus
• The International Code of Botanical Nomenclature

Development of the Kingdom Concept

Classification of Major Groups

The Species Concept
Introduction

All living organisms given two-word Latin
scientific name = species name.
• Only one correct scientific name for a species.
• Many common names may be given to same
species.
–
Dicentra cucullaria - Many common names:
Dutchman’s breeches, little-boy’s breeches,
monkshood, boys-and-girls, soldier’s cap, white
hearts,…, plus others in different languages
• Or one common name may be applied to a
number of different species.
–
Monkshood is common name for Dicentra cucullaria and
for Aconitum species, which is in a different family.
Development of the Binomial System of
Nomenclature

First attempt to organize and classify plants
by Theophrastus in 4th century B.C.
• Classified nearly 500 plants by leaf characteristics


13th century - Distinction made between
monocots and dicots.
Beginning of 18th century - Details of fruit and
flower structure, in addition to form and habit,
used in classification schemes.
• Latin phrase name given to plants and animals.
–
First word of phrase indicated genus (plural: genera).
Development of the Binomial System of
Nomenclature

Carolus Linnaeus (1707–1778) - Established
Binomial System of Nomenclature
• Published Species
Plantarum, 1753
• Changed the Latin
phrases to reflect
relationships and
placed one to many
species in each
genus
–
Abbreviated names to
two parts (binomials)
Development of the Binomial System of
Nomenclature

Binomial System
of Nomenclature
• All species named
according to this
system, which
includes authority
for species name.
–
Spearmint:
Mentha spicata L.
The International Code of Botanical
Nomenclature

Book that standardizes rules governing the
naming and classification of plants
• Agreed that Linnaeus is starting point for names
• Rules revised and expanded at periodic international
botanical congresses.
• Has English, French and German translations
• Requires two steps to officially recognize new plant
species:
–
Latin description of plant must be published in a journal or
other public publication.
–
Author must designate type specimen that is deposited in a
herbarium.
Development of the Kingdom Concept

When classification schemes first developed,
organisms placed in either Plant Kingdom or
Animal Kingdom.
• The distinction works well for complex animals,
but not for simpler organisms.

Hogg and Haeckel proposed a third kingdom
in 1860’s.
• All organisms that did not develop complex
tissues were placed in Kingdom Protoctista.
Development of the Kingdom Concept

In 1938, Copeland assigned single-celled,
prokaryotic organisms to Kingdom Monera,
leaving algae, fungi and single-celled
eukaryotic organisms in Protoctista.

In 1969, Whittaker developed five-kingdom
system.
• Split Fungi from Kingdom Protista

In 1980s, Woese argued Monera should be
split into Archaea and Bacteria, resulting in
six kingdoms:
• Archaea, Bacteria, Protista, Fungi, Plantae, Animalia
Classification of Major Groups

Genera grouped into families.
• Families grouped into orders.
– Orders grouped into classes.
o Classes grouped into phyla (divisions).
« Phyla grouped into kingdoms.

Example: onion
Kingdom: Plantae
Phylum:
Magnoliophyta
Class:
Liliopsida
Order:
Liliales
Family:
Liliaceae
Genus:
Allium
Species: Allium cepa L.
Classification of
Major Groups

3 domains (superkingdoms): Bacteria,
Archaea, Eukarya

Depending on the
classification system,
between 12 and 30 plant
phyla recognized.

In-between categories,
such as subphylum,
subclass, and suborders
used; and species
sometimes further
divided into subspecies,
varieties and forms.
Classification of Major Groups

Second part of species name = specific epithet.
• Specific epithet followed by author(s) who named
the plant.

Taxonomists specialize in identifying, naming,
and classifying organisms.

Systematists incorporate evolutionary
processes to sort out natural relationships.

Dichotomous keys help identify organisms.
• Choose features from paired statements that most
closely apply to organism
The Species Concept

Morphological species concept - A species
is defined by morphology.

Interbreeding species concept - A species is
a population capable of interbreeding and is
reproductively isolated from other groups.

Ecological species concept - A species is a
group of related individuals that occupy a
unique ecological niche.
The Species Concept

Cladistic species concept - A species is
determined by phylogenetic history.
• Individuals with common evolutionary background
considered to be a species.
–
Cladistic methods used to determine evolutionary
history.
o
Examines natural relationships among organisms,
based on shared features.
o
Relationships portrayed on cladograms.
o
The value or form of a feature referred to as a
character state.
o
Hypotheses made about which state is ancestral.
The Species Concept

In trying to choose the best cladograms,
taxonomists use principle of parsimony.
• Occam’s razor - “One should not make more
assumptions than the minimum needed to explain
anything.”

Best cladogram is interpreted as that which
requires fewest evolutionary changes in taxa
involved.
The Species Concept

Eclectic species concept - Single criterion
not sufficient to identify species.
• Morphological, geographical, biological and
ecological criteria must be used when defining
species.

Nominalistic species concept - Species do
not exist.
• Evolutionary unit of importance is local
interbreeding population.
Review

Introduction

Development of the Binomial System of
Nomenclature
• Linnaeus
• The International Code of Botanical Nomenclature

Development of the Kingdom Concept

Classification of Major Groups

The Species Concept