chordate cladistics

what is clasdistics

a method of organising life into related groups called clades

what is a cladogram

a graphical representation of relationships between lineages

what is the difference between a cladogram and a phylogenetic tree

phylogenetic trees also depicts how much change there is between lineages e.g. the amount of changes to characteristics, the amount of molecular evolution, or an inference of the amount of time elapsed

how is the amount of changed depicted in a phylogeny

Branch lengths quantify the amount of change between nodes

what can a phylogeny including a time component be called

chronology

what is a character matrix

a table with rows of taxa (these could be species, families, orders, kingdoms, or even genes themselves), and columns of characters

Characters may be any observation on the phenotype

• often morphological

• nucleotides, amino acids and genes can be used as characters

what are the diagnostic features of chordates - 4

what is a plesiomorphy

primitive characters that describe the anscestral state

these can be lost and regained

there are often outgroups built in cladograms where these features aren’t present

what is a synapomorphy

These are traits held by a related group, and all their ancestors including their common ancestor

They can also be called derived characters

e.g. feathers are a synapomorphy of birds, since all birds (and their common ancestor) have feathers

is the feature of having a tail a synapomorphy or plesiomorphy of hominins and of primates

The feature of not having a tail is a synapomorphy of hominids, although having a tail is as plesiomorphy of primates

if characters of homologous what does this mean

they are related through descent

what is a homosplastic trait

if traits are similar but not due to descent, they are homoplastic

what is another term for a monophyletic group

clades

what is a monophyletic group

A group or taxon comprising a collection of organisms, which includes their most recent common ancestor and all descendents of that ancestor

what is a paraphyletic group

A taxon or group of organisms including the most recent common ancestor, but excludes some members which share that common ancestor

which of the following is a paraphyletic group

amphibians, reptiles, birds or mammals

reptiles

what is a polyphyletic group

A taxon or group whose members are descended from two or more ancestors

e.g. flying vertebrates

what is an outgroup

A group or taxon more distantly related to the group which is being investigated, and is used to identify where the root of the phylogeny is

what is a sistergroup

Monophyletic groups that are each other's closest relatives

a single branch = a monophyletic group

what is an apomorphy

the defining characteristic that evolved with a monophyletic group

what are the apomorphies of mammals that separate them from non-mamalian vertebrates

fur

mamary gland

dentary/squamosal joint

what are the living sister group of birds

crocodalia

what is an extinct group of animals that are a sister group of birds

saurapods