Taxonomy,
Classification,
and Identification
Karl Hagenbuch
Department of Biological Sciences
San Antonio College
Taxonomy
= the study of naming, describing and
classifying organisms, including the
rules, theories, principles and procedures
Taxon = a group of organisms recognized
at any level of a taxonomical hierarchy
(e. g. Family, Class)
Classification= the orderly arrangement of organisms into a hierarchal
system that is derived from an accumulation of
information about the individual organisms, the end result
expressing an interrelationship
Why?
Because it provides humans with a means to address
organisms and their relationships to one another
Because it allows humans to make inferences about
unfamiliar organisms
Because it is in our nature
Classification
Systems:
Artificial = based on obvious or convenient items of
information called characters (e.g. flower color, locality).
Natural = based on morphological features that
give the sense of correlation with those of
another organism. (e.g. trees, grasses)
Phylogenetic = based on the proposed lineage
derived from a wide variety of information.
Aristotle
Greek Philosopher
First to propose a system
of classification
Scala Naturalae
Two types of animals:
• With blood
• Without blood
Theophrastus
Greek Philosopher
Father of plant taxonomy
Classification of plants
was based on:
• Mode of generation
• Locality
• Size
• Usefulness
Carl von Linné
Swedish botanist, zoologist, and
physician
First to illustrate the usefulness
of binomial nomenclature
Developed the modern
taxonomic hierarchy
Modern Hierarchy
(Biological Classification)
• Domain – Eukarya
• Kingdom – Animalia
• Phylum – Cordata
• Class – Mammalia
• Order – Primates
• Family – Hominidae
• Genus – Homo
• Species – Homo sapiens
• Current system recognizes 3 Domains:• Eukarya:
– Kingdom Animalia– Kingdom Plantae– Kingdom Fungi
• Archaea & Bacteria
• The previously recognized Kingdoms ofProtista & Monera have been dissolved
Modern Taxonomic Hierarchy
Carolus Linnaeus
= a two-word name consisting of a generic name and a specific epithet
Binomial Nomenclature
Specific epithets:
Descriptives – Quercus macrocarpa
= Oak with big fruit
Honorifics – Quercus buckleyi
= Oak named for Mr. Buckley
Localities – Quercus virginiana
= Oak first described in Virginia
Phylogenetic Classification= the evolutionary history of a species or group of species
Typically represented as
a phylogenetic tree
(cladogram) a branching
diagram showing the
evolutionary
relationships among
various biological
species or other taxa
that are believed to have
a common ancestor
The Pylogenetic Tree
Time
Species 1 Species 2 Species 3
Plant Classification
Current classification systems follow the recognized
taxonomic hierarchy, however, there is always some
disagreement as to the membership requirements of
various taxa
The Core
Gymnosperms and Angiosperms
Angiosperms
• plants with vascular (circulatory) tissues
• they produce flowers
• reproductive unit is a seed produced within an
enclosed ovary
Gymnosperms• plants with vascular (circulatory) tissues
• they lack flowers
• reproductive unit is a seed produced on scales
in a cone-like structure
Non-vascular Land Plants
Non-vascular land plants
• reduced plants that lack vascular
(circulatory) tissues
• they neither have flowers nor produce
seeds
• reproductive unit is a spore
Ferns
Ferns and fern allies
• plants with vascular (circulatory)
tissues
• they neither have flowers nor produce
seeds
• reproductive unit is a spore
Identification
= the assigning of an existing name to an
unknown organism
Methods
Expert assistance – local university,
school, museum
Comparison method – guide books,
internet
Dichotomous key – local manuals, floras
Dichotomous Key
Keys based on a sequence of pairs of
contrasting statements
The user chooses the statement that better
describes the plant in question
Each time a choice is made a number of plants
are eliminated
Eventually the number of possible
identifications is reduced to one
Dichotomous Key
1. Growth habit an herb
1. Growth habit a vine, shrub or tree
. . . . . . . . . . . . 2
. . . . 4
4. Growth habit a vine
4. Growth habit a shrub or tree
. . . . . . . . . . . . 5
. . . . . . . 7
7. Growth habit a shrub
7. Growth habit a tree
. . . . . . . . . . . . 8
. . . . . . . . . . . . 30
Dichotomous Key
30. Leaf arrangement opposite
30. Leaf arrangement whorled or alternate
. . . . Fraxinus
. 31
31. Leaves simple
31. Leaves compound
. . . . . . . . . . . . . . . 32
. . . . . . . . . . . . 44
32. Venation palmate
32. Venation pinnate or reticulate
. . . . . . . Washingtonia
. . . . . . 33
Leaf Types
Leaf Types
Leaf Types
Leaf Types
Leaf Types
Dichotomous Key
33. Margin entire
33. Margin toothed
. . . . . . . . . . . . . . . 34
. . . . . . . . . . . . . . 39
34. Lobes present
34. Lobes absent
. . . . . . . . . . . . . . . 35
. . . . . . . . . . . . . . 37
35. Blades palmately lobed
35. Blades pinnately lobed
. . . . . Platanus
. . . . . . . . . 36
Dichotomous Key
36. Lobes rounded
36. Lobes pointed
. . . Quercus macrocarpa
. . . . . Quercus buckleyi
Thank You
It is both an honor and pleasure to
speak before the Master Naturalist
I wish you all continued success