Evolution: Lecture 6 Flashcards
What is systematics?
The study if the diversity of life. Trying to work out all our information about it.
What are the two components of systematics?
Taxonomy and Phylogenetics
What is taxonomy?
Naming and identification of taxa: species and groups of species. The identification of taxa and categorization of taxa to house species.
- Family, orders, domains
What is phylogenetics?
An estimation of the influence of evolutionary trees (phylogenetic trees or phylogenies)
what are the taxa in increasing specificity?
Domain
Kingdom
Phylum
Class
Order
Family
Genus
Species
What are taxa?
They are groups of similarities between organisms. It is highly based on Linnaean evolution. Each taxa are groups of other (smaller) taxa.
What kind of name do we give spices?
Binomial nomenclature. Made up of genus and specific epithet.
Panthera pardus
Why do we use such unique names?
We use unique names that mean the same thing to all scientists. They would stay the same regardless of the language.
What supports taxonomy and phylogeny?
Hierarchical nested taxonomy is consistent with the tree of life. It is also the part of Linnaean’s ideas that worked well with Darwin’s ideas.
Biologists consider that?
Most biologists today consider that taxonomy should reflect phylogeny.
What are phylogenetic trees?
A branching tree diagram that communicates relationships between organisms/evolving things.
Tips and Branches and sister taxa?
- Tips are normally representative of living species
- Branch points or internal nodes represent the common ancestors
- Sister taxa are species that branch from the same ancestor
Cladogram?
A phylogenetic tree where branch lengths have no particular meaning.
Phylogram?
Where branch lengths represent inferred amount of evolutionary change or time.
- Very useful for molecular phylogenies.
Monophyletic group (clade)?
An ancestor and all of its descendants.
Example: snipping off a full branch
Paraphyletic group?
An ancestor and some, but not all, of its descendants
Example: snipping off a branch and getting rid of a twig on it
Polyphyletic group?
A group that does not include its own most recent common ancestor (= 2+ branches artificially grouped together)
Example: grabbing a bunch of twigs and holding them together like a branch
Many biologists also consider?
Taxonomy should reflect phylogeny and taxa should be monophyletic groups when possible.
How do we infer phylogenies?
Character states (possible homologies)
– Morphological features, etc.
– Identities in DNA / protein sequences
Distribution of character states among organisms reflect evolutionary relationships
What do we look at for the distribution of character states?
We look at the distribution (among organisms) of a characteristic by observing the different states of it.
Example: Non-retractable vs retractable claws.
What are the 2 options for a state of a character?
- There is the original (ancestral) state
- There was an evolutionary change where the ancestral state changed into a new one (derived state).
Shared derived states?
Imply relationships. Evidence that they are closer to each other than the ancestral states.
Shared ancestral states?
do not imply relationships.
What is the outgroup comparison?
Outgroup comparison (usually) to distinguish ancestral and derived states
