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

http://static.newworldencyclopedia.org/7/70/Phylogenetic_tree.svg

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