Phylogeny and Systematics Flashcards

Flashcards for reviewing Phylogeny and Systematics in Evolutionary Biology

Systematics

Branch of biology concerned with diversity of life and reconstruction of phylogenetic histories

Taxonomy

Nomenclature, identification, and classification of species; a component of systematics

Purpose of Taxonomy

To arrange organisms in categories that reflect phylogeny

Linneaus

Developed binomial nomenclature and a system of taxonomic categories

Binomial Nomenclature

Scientific name

Taxon

A taxonomic group of any rank

Taxonomic Kingdoms

Kingdoms of life; includes Protista, Plantae, Fungi and Animalia

Goal of Systematics

Classify species based on evolutionary affinities

Monophyletic Group

Includes all descendants of a single common ancestor

Paraphyletic Group

Includes some, but not all, of the descendants of a single common ancestor

Polyphyletic Group

A group that is not based on common ancestry

Monophyletic Taxon

A single ancestor gave rise to all species in that taxon and to no species placed in any other taxon

Paraphyletic Taxon

Excludes species that share a common ancestor that gave rise to the species included in the taxon

Polyphyletic Taxon

Members are derived from two or more ancestral forms not common to all members

Homology

Likeness attributed to shared ancestry

Analogy

Similarities due to convergent evolution not common ancestry

Convergent Evolution

Acquisition of similar characteristics in species from different evolutionary branches

Molecular Systematics

Protein comparison, DNA comparison, Molecular clocks

Molecular Clock

Steady rate of change in DNA sequences over time, providing a basis for dating the time of divergence of lineages if the rate of change can be estimated

Phylogeny

Represents an estimate (hypothesis) of evolutionary relatedness

Phylogenetic Tree

May be a cladogram, but may also include information about the amount of evolution in each lineage

Phenetics

Makes no evolutionary assumptions; decides taxonomic affinities entirely on the basis of measurable similarities and differences

Phenetics Data

Comparisons are made using anatomical characteristics without sorting homology from analogy

One Criticism of Phenetics

Overall phenotypic similarity is not a reliable index of phylogenetic proximity

Cladistics

Organisms are classified according to the order in time that branches arise along a phylogenetic tree

Cladistics Divergence

Degree of divergence is NOT considered

Cladogram

Used in Cladistics, Tree with a series of dichotomous forks

Classical Evolutionary Taxonomy

Attempts to balance the criteria of phenetics and cladistics by considering overall homology along with branching sequence

Bases of Classical Evolutionary Taxonomy

Morphology and DNA and protein comparisons

Phylogenetic Tree Branch Point

Each branch point represents the divergence of two species

Sister Taxa

Groups that share an immediate common ancestor

Rooted Tree

Includes a branch to represent the last common ancestor of all taxa in the tree

Polytomy

A branch from which more than two groups emerge

Plesiomorphic (ancestral) Character States

Character states that originated earlier in the evolutionary history of a group

Apomorphic Character States

Character states that originated later; called advanced or derived

Shared Ancestral Character

Character that originated in an ancestor of the taxon

Shared Derived Character

Evolutionary novelty unique to a particular clade

Outgroup

Species or group of species that is closely related to the ingroup

Plesiomorphic Characters

Primitive characteristics shared among all of the species of the cladogram and with the common ancestor

Symplesiomorphy

Sharing of ancestral states

Apomorphic Characters

Derived characteristics which are homologies that evolved after a branch diverged from the phylogenetic tree

Synapomorphy

Derived state that is shared by two or more species

Synapomorphy significance can identify a monophyletic group all the descendants of a single common ancestor that possessed the derived state of the character.

Synapomorphy significance

Phylogenetic Inference

Process of developing an estimate of the evolutionary history of a group of organisms

Characters

Physical characteristics of a group of organisms

Homologous State

State that has evolved only once is called homologous in all the species that share it

Homoplasious States

Character states that arise more than once

Maximum Parsimony

Tree that requires the fewest evolutionary events is most likely

Maximum Likelihood

Tree can be found that reflects the most likely sequence of evolutionary events

Computer Program Use

Computer programs are used to search for trees that are parsimonious and likely

Advantage of Maximum Likelihood

Estimation of the pattern of evolutionary history can take into account probabilities of character state changes from a precise evolutionary model

The bootstrap probability (Pb)

Used to check the reliability of a phylogenetic tree