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Introduction
I. Taxonomy - science of classification including its bases, principles,
rules and procedures.
A. Its general purpose is to arrange plants in such a way as to provide an
information retrieval system, i.e. the name and rank or position in an ordered
hierarchy tells us something about the plant.
B. Taxonomy is probably the oldest science - plants classified as poisonous
vs. edible.
C. Classification is a natural occupation of humans and one of the most
necessary of pastimes. It is essential to our daily lives and is started
almost as soon as we're born. We need to classify and name things so we know
that we're talking about the same things.
"A plants name is the key to its literature", "A
plants name is the key to its literature", i.e. it is the key to what
we know about it.
D. Taxonomy is a very dynamic and synthetic science and is basic to all
other sciences, yet at the same time dependent upon them, i.e. the information
used by taxonomists is gathered using information from other disciplines such
as genetics, ecology, morphology, anatomy, physiology, etc.
On the other hand, all other sciences are dependent on taxonomy, e.g.
other disciplines must have the correct name of organisms they are working
on, e.g. cancer drugs or antibiotics.
I. Understand taxonomic principles and concepts.
II. To be able to collect and prepare herbarium specimens.
III. To be able to identify plants. There are four ways to identify
plants: ask someone, memorize all 250,000, comparison, or learn how to identify
them.
A. Identification requires:
1. vocabulary universal to all plants of the world.
2. learning common plant families. This makes identification easier and
it is also necessary to understand taxonomic principles and plant evolution.
IV. Become familiar with computer processing of information, email and
internet.
Systematics
I. Traditionally taxonomy was based largely on gross morphological features,
however now virtually all other scientific information is used from a wide
variety of fields such as anatomy, genetics, ecology, physiology, molecular
biology, cytology, chemistry, reproductive biology, etc.
A. taxonomists now generally try to construct classifications which reflect
the phylogeny of their taxa.
1. Phylogeny - the evolutionary history of a group.
2. Taxon (taxa) - a taxonomic group of any rank, e.g. family,
genus, species, subspecies, etc.
II. This has led to a much broader term for the activities of taxonomists.
A. Systematics - the scientific study of the kinds and diversity of
organisms and any and all relationships among them.
1. Includes not only the traditional activities of taxonomy but also the
investigation of such things as evolution, speciation, natural variation,
reproductive biology, and a variety of biological phenomena.
2. However, there is much disagreement on the technical differences
between taxonomy and systematics and they are often used interchangeably.
Major objectives of plant systematics
I. Provide a convenient method of identifying, naming, and describing
plant taxa.
II. Provide a classification scheme which attempts to express
phylogenetic relationships.
A. This gives predictive value.
III. Provide an inventory of plant taxa, e.g. Floras.
IV. Provide an understanding of evolutionary processes and relationships.
Phases of plant systematics
I. Pioneer - discovery and collection phase, still going on in tropics.
II. Consolidation - synthesis, mostly based on morphology, of field
and herbarium in preparation of floras and form based classification systems.
III. Experimental or biosystematic - analysis of a wide variety of things
such as reproductive systems, variation patterns, chemical, cytological,
genetic, fertility relationships, or evolutionary patterns.
IV. Encyclopedic or holotaxonomic - analysis and synthesis of all
information and types of data to develop classification systems based on
phylogenetic relationships.
A. Phases I and II are often called alpha taxonomy.
B. Phase IV is often called omega taxonomy.
V. Systematics is a dynamic science, a "never ending synthesis".
New technologies constantly provide new data which causes constant re-evaluation
of classification schemes.
Fundamental components of taxonomy
I. Classification - arrangement of groups of plants with particular
characteristics by rank or position according to certain criteria.
A. Placing them within the taxonomic hierarchy, an information storage and
retrieval system.
1. The taxonomic hierarchy
Kingdom
Phylum (Division)
Class
Order
Family
Genus
Species = genus + specific epithet
2. Binomials - Linnaeus (mid 18th century) developed
binomial naming system:
a. Each species has a two part name, e.g. the scientific name
for humans is Homo sapiens
b. The first part of a binomial is the genus, e.g. Quercus
is the genus of oak trees
c. The second part of a binomial is the specific epithet,
usually a latinized descriptive. E.g. Quercus alba, Q.
nigra and Q. rubra are the white, black and red oaks,
respectively
d. Note that a
specific epithet is meaningless without the genus name
e. Scientific names are always latinized and either italicized or
underlined, and the first letter of only the genus name is capitalized
B. Three basic classification systems for plants:
1. Artificial - utilitarian, i.e. constructed for a specific
purpose and based on one or a few characters such as habit, color, form, or
edible vs. poisonous.
2. Phenetic - based on overall similarity (numerical).
3. Phylogenetic - based on common evolutionary descent.
C. Classification includes the determination of position or rank for new
taxa as well as old taxa which have been remodeled, divided, united,
transferred or altered in rank.
II. Identification - the assignment of additional unidentified plants to
a correct rank once a classification has been established. It is the
determination of a name for a specimen. This also implies its rank. Most widely
used system of identification is the dichotomous key which consists of
successive contrasting statements.
III. Description - it is a statement of attributes for a taxon. Many
types of characters are recorded for the plants. This serves to distinguish them
from other plants and taken together the terms used provide a vocabulary for
communication about plants.
IV. Nomenclature - a precise and universal system of rules used by all
botanists of the world for naming plants.
A. Governed by International
Code of Botanical Nomenclature (ICBN). Not only do newly discovered plants
need names, but also the constant study of plants and synthesis of new data
frequently results in differences of opinion concerning past work. This often
results in splitting, uniting, changing ranks etc., all of which may affect
the plants name. Universal rules are needed to determine the correct name when
such things are done.
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