Cladistics and Phylogenetics Flashcards
Evolution
According to Darwin, evolution is descent with modification
Phylogenetic tree
Depicts hypothetical phylogeny of the taxa under consideration
Node (on phylogenetic tree)
Represents a speciation event
Internode (on phylogenetic tree)
Line connecting two speciation events and representing at least one ancestral species
Selection
Process which favors one feature of organisms in a population over another feature found in the population. This occurs through differential reproduction (those with the favored feature produce more offspring than those with the alternative feature, such that they become a greater percentage of the population in the next generation)
Biological classification
The orderly arrangement of organisms in a hierarchical system that ideally reflects evolutionary history
Phylogeny
The evolutionary relationships among organisms
Systematics
Field of biology that deals with the diversity of life. Consists of the areas of phylogenetics and taxonomy
Taxon (plural taxa)
Any named group of organisms that is not necessarily a clade
Taxonomy
The science of naming and classifying organisms
Phylogenetics
The field of biology that deals with the relationships between organisms, the discovery of these relationships, and the study of the causes behind these relationships
Cladistics
Organisms grouped strictly on homology. Trees are based on genealogy and not just similarity.
Apomorphy
A derived character
Synapomorphy
A shared derived characteristic used to infer ancestry and thus construct clades
Autapomorphy
A unique derived characteristic not shared with any other taxon
Plesiomorphy
An ancestral character state for the taxa under consideration
Symplesiomorphy
An ancestral character shared by the taxa under consideration
Character state
Describes a character in terms of its state, e.g. hair present
Character
A heritable trait
Polarity of characters
The states of characters used in a cladistic analysis, whether ancestral or derived
Analog
A feature that appears similar in two taxa that have originated from two different ancestors
Homoplasy
A character shared by a set of species but NOT present in the common ancestor
Homolog
A feature that appears similar in two or more taxa with a common ancestor that also possessed that feature
Homology
Two structures are considered homologous when they are inherited from a common ancestor which possessed the structure
Clade
A monophyletic taxon – a group of organisms that includes the most recent common ancestor of all its members and all of the descendents of that most recent common ancestor
Cladogenesis
The development of a new clade; speciation
Cladogram
A diagram that depicts hypothetical lineages leading to the taxa under consideration
Convergent evolution
An evolutionary change producing similar characteristics in two or more distantly related forms because of their separate adaptation to common ecological conditions
Hypothesis
A concept or idea that can be falsified by various scientific methods
Ingroup
In a cladistic analysis, the set of taxa that are hypothesized to be more closely related to each other than any taxa are to the outgroup
Outgroup
In cladistic analysis, any taxon used to help resolve the polarity of characters, and which is hypothesized to be less closely related to each of the taxa under consideration than any are to each other.
Lineage
Any continuous line of descent
Monophyletic
Term applied to a group of organisms which includes the most recent common ancestor and all of its descendants. Also known as a clade.
Paraphyletic
Term applied to a group of organisms which includes the most recent common ancestor but NOT ALL of the descendants
Polyphyletic
Term applied to a group of organisms which does NOT include the most recent common ancestor
Sister group
The two clades resulting from the splitting of a single lineage
Parsimony
A rule used to choose among possible cladograms – the cladogram that implies the least number of changes in character states is the best cladogram
