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Classification and Systematics (concepts (systematics to understand each…
Classification and Systematics
concepts
phylogeny
hereditary relationships of any group of organisms
systematics
to understand each of the evolutionary lines of a plant
ex: legume family (peas, beans, & lentils)
nomenclature
system of names that reflects their relationships accurately
natural system of classification
system in which closely related organisms are classified together
assigned plant names on the basis of phylogenetic relationships
levels of taxonomic categories
species
most fundamental level of classification
ideally & theoretically is a set of individuals closely related by decent from a common ancestor
genus
closely related species are grouped together
monophyletic
natural; all species in genus are related by a common ancestor, & all descendants of the common ancestor are in the same genus
polyphyletic
unnatural; members may have evolved from different ancestors & resemble each other only as a result of convergent evolution
family
composed of one, several, often many genera
order, class, division & kingdom
all lvls except for kingdom must have certain endings to indicate classification level
species epithet
the word distinguishes this species only from the other species of the genus
taxon
refers to any taxonomic group such as species, genus, family, & so on
cladistics
method of analyzing these phylogenetic, evolutionary relationships
synapomorphies (homologous)
features similar to each other because they have descended from a common ancestral feature
homoplasies (analogous)
convergent evolution can cause natural selection to favor mutations in two difference lines of plants causing them to have similar phenotypes
cladogram
a diagram that shows evolutionary patterns by means of series of branches
node
point at which a cladogram branches
common ancestor
represents the descendants of the original group
clade
any ancestor (node) & all of the branches that lead from it
apomorphy
a feature present in one or several derived members of a group, but not present in the ancestral members
paraphyletic group
one that does not contain all the descendants of the most common ancestor
parsimony
prefer the simplest hypothesis, & do not make a hypothesis any more complicated than it needs to be
equally parsimonious
several equally simple cladograms but have taxa arranged differently
unresolved polychotomy
not enough data, & usually the various species are shown arising from the same node
basal angiosperms
living descendants of those early-diverging clades
eudicots
the rest of the dicots
other types of classification systems
artificial classification system
several key characters, often very easy to observe, are chosen as the basis of classification
ex: picture guides to birds, plants, & mammals
classification systems for fossils
combines features of both
artificial classification
&
natural systems
form genera
superficially similar fossils are grouped together
taxonomic studies
type specimen
a single specimen that is the absolute standard for the species & its scientific name
isotype specimen
a specimen obtained from the same plant/clone as the type specimen
major lines of evolution
grade classification
based on levels of evolutionary advancement
ex: protistans were placed together bc they had low lvl (low grade) of evolutionary advancement
kingdom Plantae
established clade of true plants
