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.

• Species Naturae & 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 ..... 22. Petals red ............ Plant B

2. Petals white ........ Plant C