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Cladistic Analysis (Biol112)
Terms in this set (41)
A discipline focused on classifying organisims and determining their evolutionary relationships. Scientists use fossils, molecules, and genes to infer evolutionary relationships. In doing this, they are constructing a "tree of life."
How organisms are named and classified.
The first person to invent a taxonomy scheme. Aristotle's "method of logical division" is useful in identifying organisms; not used in taxonomy today.
"method of logical division"
Aristotle's way of classifying organisms. Done by asking a series of questions about the organism. Used today in taxonomic keys to identify species.
A series of questions used by biologists to identify an organism.
In working with plants, deduced that morphology alone was not enough to tell whether you have 1 or 2 different species. I.e., with plants, nutrients can determine whether a willow will appear as a shrub or a tree - but it's the same species.
biological species concept
Morphology alone does not tell you whether an organism is of the same species; you must look at other aspects.
Concept introduced by Ray in 1680s. If you can take two plants and "mate" them and they have offspring, they are the same species. If not, they are different species.
limitations of concept
Reproductive isolation only applies to organisms that sexually reproduce; many reproduce asexually, so this does not work for them.
Linnaeus (1735, 1753)
Created binomial nomenclature system. Also grouped species in a hierarchy of increasingly inclusive categories (not the first to do this, but did this most completely).
"many name" in Latin. Before advent of binomial nomenclature a descriptive name was used for organisms, using Latin words because of the ambiguity and changing nature of "living" languages, such as English. (Latin is a "dead" language.)
Nepeta floribus interrupte spicatus pedunculatis
"Mint with flowers with interrupted pedunculate spike." An example of a "polynomial" used to describe a kind of mint flower.
genus (pl. genera)
First part of the binomial name; one step broader than species. "Genus" concept was used previous to Linnaeus.
Genus + specific epithet/modifier. The first part is the genus to which the species belongs; the second part is unique to each species. Avoids ambiguity when talking about organisms. First letter of genus capitalized; entire binomial italicized. Concept introduced by Linnaeus.
Increasingly inclusive categories which are used to categorize and organize organisms.
taxonomic ranks / taxa (s., taxon)
The named taxonomic unit at any level of the hierarchy. Taxa broader than genus are not italicized, although they are capitalized.
Order of taxonomic hierarchy
species, genus, family, order, class, phylum, kingdom, domain
Louis Agassiz (1807-1873)
Agassiz thought taxonomy revealed a grand design in nature -- God's thoughts.
Charles Darwin (1809-1882)
Darwin thought taxonomy revealed a grand design in nature -- evolution.
The evolutionary history of a species or group of species.
Evolutionary history represented in a branching diagram called a phylogenetic tree. Represents hypothesis about evolotionary relationships. Each branch point represents the divergence of two evolutionary lineages from a common ancestor. Are inferred from morphological and molecular data.
Used to infer phylogenetic relationships.
Used to look at similarities of organisms.
Analogous structures that arose independently, as a result of convergent evolution (see "analogy").
Similarities due to shared ancestry. I.e., similarity in number and arrangement of bones in forelimbs of mammals is an example of morphological homology. Genes/DNA sequences are homologous if they are descended from sequences carried by a common ancestor. Complexity of an organism also plays a role.
Similarity due to convergent evolution, rather than shared ancestry (homology). Convergent evolution occurs when similar environment produces similar adaptations in organisms from different evolutionary lineages. I.e., bats and birds.
Scientists use morphologies of embryos more than adult species (in taxonomy) because they are less specialized.
Similarities between DNA sequences of species. Scientists use computer programs to help align sequences and determine whether specific deletions have made small differences in the species' genes. I.e., a sequence shifts back a nucelotide compared to another. "Shared systematics" uses DNA and other molecular data to determine evolutionary relationships.
protein; DNA similarities
Used in creating phylogenetic trees now, to determine common ancestry/relationships.
See "numerical taxonomy," "evolutionary taxonomy," and "cladistics." (These are the three classification schemes.)
phenetics / numerical taxonomy
Classify organisms based on overall similarity, usually morphology or other observable traits, regardless of phylogeny/evolutionary relation. Original classification method.
Classification of organisms based on combination of phylogenetic relationship and overall similarity. Second classification method.
An approach to taxonomy where common ancestry (phylogeny) is the primary criterion for classifying organisms. Most current classification method.
A group into which biologists place species; includes an ancestral species and all of its descendants.
A group into which biologists place species; includes an ancestral species and all of its descendants. Synonymous with "clade."
Group consisting of an ancestral species and SOME of its descendants, but not all.
group of species, some of which have different ancestors
shared ancestral character
character that originated in an ancestor of the taxon
shared derived character
character that is unique to a particular clade
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