Topic 1: Phylogenetics and Cladistics Flashcards
How do we know the northern pigmy owl is more related to dinosaurs than crocodiles
birds and dinosaurs share a more recent common ancestor than to crocodiles. Shown through similar morphological characteristics, molecular characteristics, and phylogenetic trees.
what’s phylogeny?
Hypotheses of the evolutionary history between species.
what’s taxonomy?
the scientific discipline of naming and classifying organisms
What is binomial nomenclature, Genus and specific epithet in taxonomy
Binomial nomenclature is a two part scientific naming system for species. Is the full species name, Genus is the first part. Specific epithet is the second part.
what are the naming conventions with binomial nomenclature? (upper case, lowercase etc)
Genus is always capitalized, specific epithet is always lowercase, and the entire binomial is italicised.
whats the order of hierarchial classification broadest to most specific?
Domains, Kingdoms, phyla, classes, orders, families, genera. Dear king philip comes over for good soup
what’s a phylogenetic tree
it’s a hypothesis presenting the evolutionary relationship of a group of organisms
what does each branch point on a tree represent?
common ancestry
whats sister taxa
groups of organisms that share an immediate common ancestor not shared by other groups.
basal taxon
a lineage that diverges from all the other members of its group early on is called the basal taxon.
what do phylogenies not tell us, what do they?
don’t tell us phenotypic similarity, the ages of the taxa or branch points, don’t tell us who evolved from who. We can only infer that the lineages leading up to a species and its sister taxon evolved from the same common ancestor.
why can convergent evolution confuse phylogenetics?
analogous structures share similar form and function (due to environment) but they are not descended from a common ancestor
how do we evaluate molecular homologies
use computer programs to align comparable DNA sequences together similar species will have more unchanged regions. Different species will have more nucleotide changes and varying lengths of DNA (due to varying genes), mutations occur over time to change the DNA sequence.
what are homoplasies
show DNA sequences that are similar due to coincidental matches in organisms that are unrelated
cladistics
a branch of systematics that looks at common ancestry
clades
consist of the ancestral species and all of its descendants
what are the 3 main kinds of clades describe them
- monophyletic: contains an ancestral species and all of its descendants. (mono=one 1 ancestor for all species)
- Paraphyletic: consists of ancestral species and some but not all it’s descendants (para= part/some)
- Polyphyletic: includes distantly related species but not their recent common ancestor. (poly= many, more than one different ancestor)
shared ancestral characteristics, what is it how do you identify it?
a character shared by members of a clade that originated in an ancestor that is not a member of that clade. (basically look if ancestor (outgroup) of clade has trait -if yes ancestral)
shared derived characteristic
a character that evolved after the ancestor, it’s unique to the clade (ancestor (outgroup) doesn’t have characteristic).
outgroup and ingroup
species or group of species that is known to have diverged before the lineages we’re interested in (ingroup).
grade
Organisms that share same level of organizational complexity or key adaptations is called a grade
maximum parsimony
the simplest explanation is the most likely -fewest evolutionary events (changes)
maximum likelihood
identifies the tree most likely to be produced given a set of DNA data
difference between cladogram and phylogram
cladogram (more common) depict only branching patterns (order), only conveys relationship based on shared derived characteristics, not when species diverged from each other. branch lengths and order don’t tell us anything. Phylograms also depict evolutionary patterns but branch lengths are proportional to evolutionary change. Longer branches mean more nucleotide changes (for those w/ DNA data)
what are some things we can use phylogenies for?
DNA forensics (to track down illegal poaching), Universal Species identification, inferring gene flow within populations, and characterizing and naming a new species by knowing where it fits in in the tree of life.
