Lecture 10 Flashcards
Define taxonomy
the theory and practice of classification and naming
define systematics
the study of biodiversity and the evolutionary relationships among organisms
Carolus Linnaeus
1707-1778
- father of taxonomy
- binomial nomenclature
- hierarchical system of classification
define a taxon
a single named taxonomic unit at any level (plural = taxa)
7 taxa
kingdom (kingdoms)
phylum (phyla)
class (classes)
order (orders)
family (families)
genus (genera)
species (species)
what is the purpose of a biological classification?
- a name is key to shared information on an organism (eg scientific literature, field guides)
- therefore has predictive power
- enables interpretation of origins and evolutionary history
systematics research requires
a robust and stable system for classifying organisms (i.e. taxonomy)
describe how phylogenies arise/what they are made up of
- individual organisms within a population
- parents produce offspring
- lines of descent persist across generations
- a population is an aggregation of the genetic lineages of the individuals they contain
- a species is made of many populations, linked by gene flow
- individual species split to give rise to multiple species
- a phylogeny shows the relationships and evolutionary histories of species
node
corresponds to historical lineage splitting events, when one lineage splits into two
branches/ edges
correspond to single ancestor-descendant lineages. All branches are connected by nodes
tips/leaves/terminals/OTUs
tips do not have represented descendants. can be individuals, species, clades
internal vs external branches
external branches (aka terminal branches) connect a tip and a node. internal branches connect two nodes
root
- a node representing earliest time point in the diagram
- often represented by an unlabelled branch
sister groups/taxa
those that are immediate descendants of the same ancestor, eg sister species, sister branches, sister clades
parents and daughters
parent branches give rise to daughter branches
ingroup
consists of the focal species in a phylogenetic study
outgroup
a more distant relative of the in-group taxa; can help to root the phylogeny and determine what character states are ancestral
MRCA
most recent common ancestor; the youngest node that is ancestral to all lineages in a given group of taxa
clade
- any piece of a phylogeny that includes a MRCA and all of its descendants
- i.e. any piece of a phylogeny that exhibits monophyly
monophyly
- describes a group made up of an ancestor and all its descendants
- ie a monophyletic group or clade
paraphyly
- describes a group made up of an ancestor and some (but not all) of its descendants
- ie a paraphyletic group or grade
polyphyly
- describes a group that does not contain the most recent common ancestor of all members
- ie. a polyphyletic group
for the species in a clade a trait is ancestral if
it was inherited in its present form from the MRCA of the clade
for the species in a clade, a trait is derived if
it originated within the clade, ie in a descendant of the clade’s MRCA