Systematics: The Science Of
Biological Diversity
Chapter 12
• Systematics- the
scientific study
of biological
diversity and its
evolutionary
history.
Theophrastus (370-285 B.C.)
• Father of Botany, student of
Aristotle.
• Classified plants based on form.
– Tree
– Shrub
– Undershrub
– Herb
Atropa belladonna- Solanaceae
Carol von Linné (1707-1778)
• Swedish naturalist.
• Systema Naturae & Species
Plantarum.
– Plant descriptions.
– Plant binomials- a two-term
system of nomenclature.
• Genus and species (specific
epithet).
• Example- catnip.
– Nepeta cataria L.
– “Nepeta floribus interrupte spicatus
pedunculatis”
Nepeta cataria- Lamiaceae
Taxonomy
• Taxonomy- (gr. taxis- arrangement, nomos- law)
the science of the classification of organisms.
– Identifying, naming, classifying organisms.
• Domain
• Kingdom
• Phylum- phyta
• Class- phyceae
• Order- ales
• Family- aceae
• Genus
• Species
Prokaryotes and Eukaryotes
Prokaryotes
Eukaryotes
Eukaryote Lineages
Origin of Cells
Origin of Eukaryotic Cells
Species Concepts
International Code of Botanical
Nomenclature (ICBN)
• Aim- to provide a stable method of naming
taxonomic groups.
– Principle I- botanical nomenclature is independent of
zoological and bacteriological nomenclature.
– Principle II- names of taxonomic groups are
determined by means of nomenclatural types.
– Principle III- nomenclature of a taxonomic group is
based upon priority of publication.
• Naming- the purpose of giving a name to a
taxonomic group is not to indicate its
characters or history, but to supply a means of
referring to it and to indicate its rank.
Taxonomic Terminology
• Taxon- a taxonomic group of any rank (plural: taxa).
• Synonym- two or more names that apply to the same
taxon.
• Basionym- the original name of a taxon.
• Author/s- the first person or persons to describe a taxon.
• Revisionary author/s- the person or persons that
modified the name.
• Etymology- the derivation, origin, or history of a word.
• Type Specimen- a specimen designated to serve as a
reference point for a scientific name.
– Holotype
– Lectotype
Taxonomic Names
• Species names consists of the genus
name, plus the specific epithet.
• Members of a species may be grouped
into subspecies or varieties.
How do you identify plants?
• Ask an expert.
• Use a herbarium.
• Compare plant with a written
description.
• Use books to picture I.D. specimens.
– Photographs and illustrations.
• Use a dichotomous key.
Dichotomous Keys
• A method employed for identifying
unknown organisms.
• A dichotomous key is constructed of a
series of couplets, each consisting of
two separate statements.
1. Flowers white .................. Plant A
1. Flowers red or yellow .....
2
2. Petals red ............ Plant B
2. Petals white ........ Plant C