Lecture 2 Flashcards
What is systematics and what is its primary emphasis?
study of species and the phylogenetic relationships among them used for classification
What is taxonomy and what is its primary emphasis?
ordering of species into formal groups based on morphological, physiological, behavioral or molecular differences
What is a lineage (clade)?
Grouping of organisms by common descent using shared derived characteristics
What does a cladogram represent?
evolutionary relationships (phylogeny) based on a common ancestor
Define a diagnostic character and enumerate its characteristics
defines a taxon and distinguishes it from relatives
* Unambiguous
* Unique
* Qualitative
* Describable (size, shape, color, etc.)
* Quantitative
* Meristic – countable
* Continuous – dividable by statistical gap coding
What is the use of genome sequencing in systematics?
Genomics
* Bioinformatics
* Comparing DNA sequences
Why are molecular clocks important in classification?
uses constant rates of evolution in some genes to estimate the absolute time of evolutionary change
Define parsimony and explain why it is one of the main criteria to prioritize cladograms
“occam;s razor”– Assumes the tree that requires the fewest evolutionary events (appearances of shared derived characters) is the most likely
Define phylogeny and give the name of the branching diagram that represents phylogeny.
Study of evolutionary relationships- Represented by a cladogram
What does a split, from one lineage to two, represent?
it represents a character change or genetic change that differentiates one species into two new species
Name the term for both a preexisting feature and a new feature
ancestral, derived
What is phylogenetic systematics (cladistics)?
study of species and the phylogenetic relationships among them
What is a monophyletic group? a paraphyletic group? a polyphyletic group?
monophyletic- sometimes called a clade, includes an ancestral taxon and all of its descendants
paraphyletic- includes a single ancestor and some of its descendants
polyphyletic- unrelated organisms descended from more than one ancestor
What does the length of branches represent in a cladogram?
sometimes, the length of a branch can reflect
the number of genetic changes that have taken
place in a particular DNA sequence in that lineage
sometimes, the length of a branch can reflect
evolutionary time
What is a character, and what are character states?
observable feature of a taxon, which may differentiate it from other taxa
States – different conditions of a feature
* Binary – presence/absence
* Multistate – >2 states
Attribute – possession of a particular state
What kind of character provides better information to recognize higher taxonomic groupings? And lower taxonomic groupings?
Higher taxonomic groupings: conservative (slowly evolving) characters
Lower taxa: rapidly changing characters
What is an analogous structure? What is a homologous structure? Which one is reliable to understand phylogenetic relations?
Analogous structures have similar function and superficial appearance, but have a different embryological origin
Homologous structures have a common embryological origin but not necessarily a similar function
Only homologous structures are reliable to determine phylogeny
