BSCI 1511 Exam 4: Phylogenics

Cladistics

a way of organizing information according to similarities, in biology it is used to assess what organisms are more similar to one another

How are evolutionary relationships determined in the absence of DNA morphology?

outward appearance (shape, structure, color, pattern) of an organism or taxon and its component parts

Phylogenetic tree

- branching diagrams used to depict hypotheses about evolutionary relationships
- a mathematical structure used to depict the evolutionary history of a group of organisms or genes

What can we not conclude from a phylogenetic tree?

- similarities because it shows historical relationships and patterns of descent
- infer the ages of the taxa or branch points shown in a tree
- assume that a taxon on a phylogenetic tree evolved from the taxon next to it

Systematics

the discipline that focuses on inferring the phylogenetic relationships of organisms and creating classifications based on their evolutionary histories
- prose that classification is based entirely on evolutionary relationships

Branchpoint

the divergence of two evolutionary lineages from a common ancestor

Sister taxa

groups that share an immediate common ancestor

Basal taxon

stems directly from overall common ancestor, evolved early, no other branches have diverged from that common ancestor

Polytomy

an unresolved pattern of divergence (has three taxons stemming from it

Outgroup

the least closely related taxon in a tree

Cladogram--
Chronogram--
Phylogram--

Cladogram: nothing is indicated by vertical axis
Chronogram: time is indicated by vertical axis
Phylogram: amount of change is indicated by vertical axis

Homologous characters

characters present in a group of species due to shared ancestry

Analogous or homoplastic characters

characters present in certain species that have evolved independently (convergent evolution)

Shared ancestral characters

characters shared beyond the taxon we are trying to define

Shared derived characters

evolutionary novelties unique to a particular clade

Phylogenetic trees are built from...

characters (or sites); can be morphological, behavioral, physiological, or molecular

Two important assumptions about phylogenetic characters

they are homologous and they are evolving independently from each other

Clades

Monophyletic groups; groups of species that include an ancestral species and all of its descendants
- can be distinguished by their shared derived characters

Paraphyletic group

consists of an ancestral species and some, but not all, of its descendants

Polyphyletic group

consist of a group of species that does not include their common ancestor