I.  Taxonomy

    A.  Identification

    B.  Nomenclature

    C.  Classification

II.  Nomenclature = System of naming things

     A.  The International Botanical Congress - every six years

          1.  Algae/Fungi/Plants Code independent from Zoological Code

          2.  Application of name determined by types

          3.  Each taxonomic unit can have only one valid name

          4.  Oldest valid name always has precedence

          5.  Names treated as Latin regardless of derivation   (Latin  Greek Dictionaries)   

          6.  Rules are retroactive from 1753
 
 

     B.  Binomial System of Nomenclature

          1. Generic Name 2. Specific Epithet 3. Authority

               Populus        deltoides          Bart. ex Marsh.

          2.  Generic Name

               a.  Always a singular, nominative case noun

               b.  Always capitalized

               c.  May be:

                    1.  Descriptive of some characteristic

                    eg. Liriodendron = lily or tulip tree

                    2.  Aboriginal name

                    eg. Following are Latin

                         Quercus = oak
                         Fagus = beech
                         Betula = birch

                    3.  Honoring some person

                         Linnaea = Carolus Linnaeus (Carl Linne')
 
 

          3.  Specific epithet

               a.  May be:

                    1.  Adjective, agreeing with generic name in
                         gender, usually indicating

                    a.  distinquishing characteristic

                         Rosa alba = white rose

                    b.  where first discovered

                         Ulmus americana = american elm

                    2.  Noun in opposition, always in nominative
                         case, but doesn't have to be same gender
                         as generic name

                         Pyrus malus = apple

                    3.  Noun in genitive singular or plural,
                         honoring a person

                         Carex davisii = honoring Mr. Davis

                    4.  From common name, genitive plural, usually
                         indicating something about habitat

                         Convolvulus sepium = of the hedges
 

III.  Plant Classification = Arrangement of plant groups in some systematic order

     A. Artificial Classification:  order facilitates identification of unknown types of plants

     B.  General Purpose Classification:  order reflects general genetic relationships and
           those morphological characters  that are easy to identify

     C.  Phylogenetic Classification:  order represents the degreee to which plant groups have evolved from one
          another or with one another (parallel evolution)

          1.  Often assumed that similarity correlates with recency of common ancestory

          2.  Assumed that best genetic relationshipss among groups of plants are reflected

taxon: a group at any hierarchical level in a classificatory system, pl. taxa.

monophyletic: of any taxon that includes its common ancestor and all and only its descendents, a monophyletic group is a clade.

polyphyletic: a taxon made up of members which, given a particular phylogenetic tree and classification based on it, includes descendents of two or more immediately unrelated ancestors, likely to be a grade.

clade: any monophyletic group of organisms

grade: a group of organisms with a similar level of organisation, paraphyletic or polyphyletic.

Cladogram (family tree) of a biological group (ancestor at the bottom).
The red and blue boxes at right  and left represent clades (i.e., complete branches).
The green box in the middle is not a clade, but rather represents an evolutionary grade,
an incomplete group, because the blue clade at left is descended from it, but is excluded.
 
 

IV.  Taxonomic heirarchy = Method of classification of plants in a  heirarchy or in an order of rank
        which corrresponds to greater and greater degrees of relatedness among members of each rank.

 Domain eg. Eukarya = most multicellular life
                    (nucleus and membrane-bound organelles)

     Kingdom  eg. Plantae = plants
                      (cellulose cell wall,chlorophyll a and b)

          Division  eg. Magnoliophyta  (Anthophyta) = angiosperms
                         (ovules enclosed in ovary)

               Class  eg.  Magnoliopsida  (Dicotyledonae) = dicots
                           (two cotyledons)

                    Order eg.  Salicales = willow (simple,
                         alternate leaves with stipules, catkins,
                         pubescent seeds)

                         Family  eg. Salicaceae (leaves deciduous,
                              dioecious, fruit 1 celled 2-4 valved
                              capsule)

                              Genus  eg. Populus (leaves as long as
                                   broad, buds covered by
                                   imbricated scales)

                                   Species eg. Populus deltoides
                                        (deltoid leaves with
                                        compressed petioles and
                                        glandular apices)
 
 

V.  What is a species?

     A.  "Recognizable and self-perpetuating population that is more or less isolated genetically as well as by its
            geographical distribution and environment"

     B.  Barriers which isolate populations genetically

          1.  Internal

               a.  expressed through incompatibility of gametes or sterile hybrid offspring

               SPECIES A   X   SPECIES B  -->>  No offspring  or,
                                                                 -->> Sterile offspring

               b.  genetic or physiologic in nature

          2.  External

               a.  Environmental

               SPECIES A grows in high mountains
               SPECIES B grows in low river valleys

               b.  Geographic

               SPECIES A grows on west coast
               SPECIES B grows on east coast

               c.  Temporal

               SPECIES A flowers in early spring
               SPECIES B flowers in late fall