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Chapter 18: Classification and Systematics (Levels of Taxonomic Categories…
Chapter 18: Classification and Systematics
Levels of Taxonomic Categories :
Genus
The genus name is the first word of a binomial scientific name (the species name is the second word) and is always capitalized.
A biological classification ranking between family and species, consisting of structurally or phylogenetically related species or a single isolated species exhibiting unusual differentiation (monotypic genus).
Species
:
Classification comprising related organisms that share common characteristics and are capable of interbreeding.
Family
#
Is one of the eight major hierarchical taxonomic ranks
A taxonomic group containing one or more genera; "sharks belong to the fish family"
Division
Order
Example:.
Carnivora (large carnivores/omnivores), and Chiroptera (bats).
Chiroptera (bats)
Cetaceans (whales, dolphins, and porpoises)
Mammalia are Primates
Order is more specific than class
Kingdom
Plant (Plantae) Kingdom
Except for kingdom, genus, and species, the names must have a certain ending to indicate the classification level
A taxonomic category of the highest rank, grouping together all forms of life having certain fundamental characteristics in common
Class
Between phylum and order
A taxonomic group containing one or more orders.
In biological classification, class is a taxonomic rank, as well as a taxonomic unit, a taxon, in that rank.
Taxon
#
Example) Some systematists study smaller taxa such as species and genera; others are concerned with higher taxa such as orders and divisions
The word "taxon" (plural taxa) is used to refer to any of the above groups in a general way
Any unit used in the science of biological classification, or taxonomy.
Taxa are arranged in a hierarchy from kingdom to subspecies
Species Epithet
#
Example) We cannot refer to tomatoes as "esculentum" because that species epithet is used for many different species in different genera
Buckwheat, Fagopyrum esculentum, and taro, Colocasia esculenta
(In binomial nomenclature) the second part, always lowercased, of a plant or animal species’ scientific name
Example) The species Quercus alba is an oak tree, as all oaks belong to the genus Quercus, but it is the specific epithet alba that identifies the particular species, which is the white oak.
The word that distinguishes this species only from the other species of the same genus
Cladistics
Cladistic studies are complicated by the fact that plants can resemble each other for two distinct reasons
2) They have undergone convergent evolution
1) They have descended from a common ancestor
Synapomorphies (Homologous Features)
Example) Almost all members of the anthurium family are easily recognizable because of their spathe and spadix inflorescence
Features similar to each other because they have descended from ancestral feature
The study of phylogeny centers on examining the similarity of one species to others
Homoplasies (Analogous Features)
Opposite of a homology
Is a shared character between two or more animals that did not arise from a common ancestor.
Should never be used to conclude that plants are closely related
Cladistics: is a method of analyzing phylogenetic, evolutionary relationships
Cladograms
Node
Each point at which a cladogram branches
Represents the divergence of one taxon into two
Also all of the branches that extend from any particular point represent the descendants of the original group
Any ancestor (any node) and all of the branches that lead from it constitute a clad
Is a diagram that shows evolutionary patterns by means of a series of branches
Other Types of Classification Systems
Classification Systems For Fossils
The goal is to understand the evolution of the fossil and to identify both its ancestors and its relatives that might have later evolved into other species
This requires a natural system
The groupings are form genera:
All fossils with the same basic form or structure are classified together
Combines features of both artificial and natural systems
Example) A piece of fossil wood similar to the wood of modern pines, spruces, and larches is classified in the form genus Pityoxylon
Artificial Systems of Classification
Typically have the goal of easy plant identification
By means of obvious characters such as flower color and plant habit
Gardeners might classify plants according to their ability to tolerate shade, full sun, frost, alkaline soils
Often very easy to observe, are chosen as the basis of classification
Are only used as adjuncts to natural systems
Therefore, all C4 metabolisms are not expected to be identical
Similarly, someone studying the metabolism of petal pigmentation might classify flowers artificially according to color, deciding to investigate the synthesis of red pigment first
As physiologists examine the phylogeny of all species with C4 metabolism, they find that C4 metabolism has evolved several times
