Plant Biology BOT3015Exam 1 Study Guide & Learning ObjectivesLecture 1: Systematics & the Tree of Life I. Systematics• Systematics: the scientific study of biodiversity and its evolutionary historyo Broad goal of systematics is to discover all the branches of the phylogenic tree of life. The significance of systematics discerns the evolutionary interrelationships among organisms, and provides the overall framework to facilitate biological information retrieval, prediction, and analysis.II. Taxonomy• The modern system of naming living things began with Carl Linnaeus. In 1753, Linnaeus published Species Plantarum in which he described each species in Latin, in a sentence limited to 12 words. These descriptive Latin names, also called polynomials, are regarded as the proper name for the species. o Linnaeus also made the binomial system (“two-term”) of nomenclature, which formed the “short hand” description for the species Ex: Solidago sempervirens L.o The International Code of Botanical Nomenclature provides the rules governing the scientific names of plants, photosynthetic protists, and fungi. The complete scientific name consists of the genus name + specific epithet + author• Ex: Solidago sempervirens L. The species name is composed of genus and specific epithet• Ex. Solidago sempervirens The specific epithet is NOT meaningful by itselfo Each name has a type specimen, which serves as a basis for comparison with other specimens in determining whether they are members of the same specieso Specimens serving as types are commonly held in herbaria• The herbarium database and website is an example of biodiversity informatics. Biodiversity informatics is the application of informatics techniques to biodiversity information o As is iDigBio, a joint project between FSU and UF. iDigBio is the National Resource for Advancing Digitization of Biological Collections. • Organisms are grouped into broader taxonomic categories arranged in a Hierarchy• Taxon (plural Taxa) is a group of any rank o Kingdom, Phylum, Class, Order, Family, Genus, Species (“Kings Play Chess On Fine Glass Stools”)o Category describes the level at which it is ranked Endings indicate rank at some levels The term “hierarchal” is used to describe taxonomic reference because it reflects the organization of nested categories.o Linnaeus’ sexual system is an artificial system of classification (e.g., everything with x stamens and y pistils grouped together). They classify organisms primarily as an aid to identification and generally by means of one or a few characters. o After Darwin’s On the Origin of Species in 1859, differences and similarities among organisms came to be seen as products of their evolutionary history, or phylogeny. Phylogeny: the evolutionary relationships among organisms. • These relationships can be diagramed as phylogenic trees.o The Angiosperm Phylogeny Group’s classification is a natural system of classification. Natural classification aims at classifying and arranging plants according to their overall hypothesized similarity and consequently can reveal their real kin relationshipso Monophyletic group (= clade): a group composed of an ancestor and all of its descendents. o Paraphyletic group: a group composed of an ancestor and some, but not all, of its descendents. o Polyphyletic group: a group that excludes the most recent common ancestor of all members. • Phylocode: an emerging, rank-free systemo There are 3 ways to apply a name to a clade:III. Cladistics• Cladistics is a form of phylogenic analysis that explicitly seeks to understand phylogenetic relationships by focusing on the branching of one lineage from another in the course of evolution• An outgroup is a taxon that is closely related to the group under study but which is not a descendent of the focal group’s most recent common ancestor.• An ingroup is the study groupo Character states possessed by closest outgroups are ancestral, while those present in the ingroup, but absent in the nearest outgroups, are considered to be derived. Present (+) Derived (-)• Construction of a cladogram (a phylogenetic hypothesis in graphical representation) is parsimonious (maximizes homologies).o Phylogenies allow one to differentiate homologous structures (i.e., those with a common origin, if not a common function) from analogous structures (those with common function, but different origins). Analogous structures are the result of convergent evolution. Homologous = same origin, different function Analogous = different origin, same function• Note that a cladogram is not a minimum spanning tree.IV. Molecular Systematics• Small numbers of genes in the plastid genome have been major sources of data for phylogenetic inference, but it is only with next generation sequencing that whole plastid genome sequencing is practical. V. Major Domains of Life and Supergroups of Eukaryotes• Analyzing the small-subunit ribosomal RNA provided the first evidence for the existence of three domains of life.• DNA is also the major source of evidence for recognition of seven supergroups in the eukaryotes. Supergroup is a rank between domain and kingdom.• Three major groups or domains: Bacteria, Archaea, and Eukaryao First recognized by in the 1970s by analysis of a small subunit ribosomal RNA by Carl Woese at the University of Illinoiso The major distinguishing features are cell type, nuclear envelope, number of chromosomes, chromosome configuration, Organelles (Mitochondria and Plastids), Cytoskeleton, Chlorophyll-based photosynthesis Table 12-3 pg. 245• Seven supergroups: Opishosonta, Amoebozoa, Plants and Algal relatives, Alveolata, Stramenopila, Rhizaria, and ExcavataVI. Identification• The Barcode of Life initiative is an approach that uses DNA, rather than morphology, for id. However, use of morphology is far more common.• A dichotomous key is constructed with couplets that are hierarchically organized. o Couplets are composed of leads that typically describe the morphology of the group of organisms. Leads are composed of strings of character x character state statements.• Converting the hierarchically organized leads into a taxon x character matrix often leads to empty character state cells.• Keys can be found in floristic treatments (a geographic focus) and monographic treatments (a taxonomic focus)o Floristic treatment: Flowers of Florida
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