VQ1 Terms

Taxonomy

A scientific discipline concerned with naming and classifying the diverse forms of life.

Taxon

A named taxonomic unit at any given level of classification.

Prokaryote

Unicellular organism that lacks a nucleus or any other membrane-bound organelle.

Sister taxa

Groups of organisms that share an immediate common ancestor and hence are each other's closest relatives.

Molecular systematics

Technique using molecular evidence to identify phylogenetic relationships.

Homologous structures

Structures in different species that are similar because of common ancestry.

Domain

A taxonomic level consisting of Bacteria, Archaea, and Eukarya.

Species

Group of populations that interbreed and produce fertile offspring.

Resolution

In microscopy: A measure of the clarity of an image; it is the minimum distance two points can be separated and still be distinguished as two points.

Field of view

In microscopy: The area that is visible when looking through a microscope.

Phylogenetic tree

A branching diagram that represents a hypothesis about the evolutionary history of a group of organisms.

Branch point

The representation on a phylogenetic tree of the divergence of two or more taxa from a common ancestor.

Magnification

In microscopy: The ratio of an object's image size to its actual size.

Contrast

In microscopy: The difference in light intensity between different parts of a sample and the background.

Outgroup

Distantly related taxon that possesses the ancestral state for all characters.

Basal taxon

In a specified group of organisms, a taxon whose evolutionary lineage diverged early in the history of the group.

Orthologous genes

Homologous genes found in different taxa as a result of a speciation event.

Phylogeny

The evolutionary history of a species or group of related species.

Horizontal gene transfer

The transfer of genes from one genome to another through mechanisms such as transposable elements, plasmid exchange, viral activity, and perhaps fusion of different organisms.

Maximum parsimony

A principle that states that when considering multiple explanations for an observation, one should first investigate the simplest explanation that is consistent with the facts.

Shared ancestral character

A character, shared by members of a clade, that originated in an ancestor that is not a member of that clade.

Shared derived character

An evolutionary novelty that is unique to a particular clade.

Cladistics

An approach to systematics in which organisms are placed into groups called clades based primarily on common descent.

Eukaryote

Organism composed of cells that have a membrane-bound nucleus and several other membrane-bound compartments.

Binomial nomenclature

Two-part, Latinized format for naming a species, consisting of the genus and specific epithet.

Basal tree

A phylogenetic tree containing a branch point representing the most recent common ancestor of all taxa in the tree.

Monophyletic group

A group of taxa that consists of a common ancestor and all of its descendants.

Paraphyletic group

A group of taxa that consists of a common ancestor and some, but not all, of its descendants.

Polyphyletic group

A group of taxa that includes distantly related organisms but does not include their most recent common ancestor.

Phylogenetic systematics

An approach to systematics in which organisms are placed into groups called clades based primarily on common descent.