Botany - Plant Names and Classification
I. Development of the Binomial System of Nomenclature.
A. All living organisms given two-word Latin scientific name = species name. (Some people refer to this as the scientific name.) 1. There is only one correct scientific name for a species. 2. Scientific names allow organisms to be identified anywhere, no matter what language is spoken
B. The problems with using common names: 1. One plant may have several common names.
An example would include species of Achimenes.
This plant is known by multiple common names, including: Magic flower, Orchid pansy, Widow's tears, Nut-orchid, Mother's tears, Cupid's Bow
2. Different (but closely related species) may have the same common name. An example would be the pepper plants. Although these plants are all “pepper,” they are actually very different plants with very different uses.
Bell pepper, a.k.a. sweet Red Chile pepper: also Black pepper, a.k.a. black peppers or pepper (in the Capsicum annuum, but a pepper corns: Piper nigrum U.K.): Capsicum annuum different variety
3. The language barrier of common names.
Onion (Allium cepa) is known as bawang besar in Brunei and Malaysia and bawang nombay in Indonesia.
But bawang is also the common plant name for garlic (Allium sativum), also known as "ahos", in the Philippines.
C. Early attempts to organize and classify plants. 1. Theophrastus in 4th century B.C. - Classified nearly 500 plants by leaf characteristics 2. 13th century - Distinction made between monocots and dicots. 3. Beginning of 18th century - Details of fruit and flower structure, in addition to form and habit, used in classification schemes. a. Latin phrase name given to plants and animals. b. First word of phrase indicated genus (plural: genera).
D. Carolus Linnaeus (1707–1778) - Established Binomial System of Nomenclature 1. Published Species Plantarum, 1753 2. Changed the Latin phrases to reflect relationships and placed one to many species in each genus a. Abbreviated names to two parts (binomials) b. The first name is the genus name. c. The second name is the species name. d. Use a capital letter for the genus and lower case for the species name. e. Use italics for a scientific name when typing; underline it when you write it. f. e.g. Spearmint: Mentha spicata 3. Included referenced list of all Latin phrase names. 4. All species named according to this system, which includes authority for species name.
E. The International Code of Botanical Nomenclature 1. Book that standardizes rules governing the naming and classification of plants 2. Agreed that Linnaeus is starting point for names 3. Rules revised and expanded at periodic international botanical congresses. 4. Requires two steps to officially recognize new plant species: a. Latin description of plant must be published in a journal or other public publication. b. Author must designate type specimen that is deposited in a herbarium.
II. Development of the Kingdom Concept A. 3 domains (super-kingdoms): Archaea, Bacteria, Eukarya B. When classification schemes first developed, organisms placed in either the Plant Kingdom or Animal Kingdom. 1. The distinction works well for complex animals, but not for simpler organisms. 2. Modifications were made over time until, in the 1980’s, Woese argued that Kingdom Monera should be split into Archaea and Bacteria, resulting in today’s six kingdoms: a. Archaea b. Bacteria c. Protista d. Fungi e. Plantae f. Animalia 3. Viruses – do not possess the attributes of living organisms, do not fit into the classification scheme 4. Lichens – are an association of an alga and a fungus, and do not fit into the classification scheme Domain Kingdom Cell type Organization Nutrition Organisms
Absorb, Unicellular-small; Prokaryotic Photsyn., Archaeacteria Archaea Archaea Lacking peptidoglycan Chemosyn.
Unicellular-small; Absorb, Bacteria, Prokaryotic Peptidoglycan in cell Photsyn., Bacteria Bacteria Cyanobacteria wall Chemosyn.
Ingestion, Eukaryotic Unicellular or colonial Protozoa, Algae Protista Photosynthesis
Fungi, yeast, Fungi Eukaryotic Multicellular Absorption Eukarya molds Plantae Eukaryotic Multicellular Photosynthesis Plants
Animalia Eukaryotic Multicellular Ingestion Animals
III. Plant Taxonomy A. Taxonomists specialize in identifying, naming, and classifying organisms. 1. Systematists incorporate evolutionary processes to sort out natural relationships. 2. Dichotomous keys help identify organisms. a. Choose features from paired statements that most closely apply to organism
B. The taxonomic rankings, from most inclusive to most exclusive, are as follows: 1. Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species 2. Memory aid mnemonic: Did King Phillip Cry Out For George’s Sword? 3. e.g. The taxonomy of the onion Domain: Eukarya Kingdom: Plantae Phylum: Magnoliophyta (Phylums were previously Divisions in plants) Class: Liliopsida Order: Liliales Family: Liliaceae Genus: Allium Species: Allium cepa L. 4. Second part of species name = specific epithet. a. Specific epithet followed by author(s) who named the plant. C. Depending on the classification system used, there are between 12 and 30 plant phyla recognized. D. Sometimes, a group of plants is so large that it necessitates subdivision of the taxonomic rankings, such as subphylum, subclass, and suborder. E. Plant species are sometimes further divided into subspecies, varieties, and forms.
IV. The Species Concept – it is surprisingly difficult to define the word "species" in a way that applies to all naturally occurring organisms, and the debate among biologists about how to define "species" and how to identify actual species is called the species problem. Over two dozen distinct definitions of "species" are in use amongst biologists. There is even a nominalistic species concept, which argues that species do not exist. A. Morphological, geographical, biological and ecological criteria must be used when defining species. B. Morphological species concept - A species is defined by morphology. C. Interbreeding species concept - A species is a population capable of interbreeding and is reproductively isolated from other groups. 1. Evolutionary unit of importance is local interbreeding population. D. Ecological species concept - A species is a group of related individuals that occupy a unique ecological niche. E. Cladistic species concept - A species is determined by phylogenetic history. 1. Individuals with a common evolutionary background are considered to be a species. 2. Cladistic methods are used to determine evolutionary history. a. Examines natural relationships among organisms, based on shared features. b. Relationships are portrayed on cladograms. c. The value or form of a feature referred to as a character state. d. Hypotheses are made about which state is ancestral. 3. In trying to choose the best cladograms, taxonomists use principle of parsimony (adoption of the simplest assumption). a. Occam’s razor - “One should not make more assumptions than the minimum needed to explain anything.” 4. Best cladogram is interpreted as that which requires fewest evolutionary changes in taxa involved. 5. Below is a simple cladogram showing the relationships of 3 species derived from a common ancestor. The cladogram indicates that Species A and Species B are more closely related to each other than either is to Species C.