L24 Taxonomy and phylogeny

classification based on 

morphology - phenetics

Common descent

branching tree with all species (extant and extinct) until primordial ancestor of life

classification

common feautres define gropu

tpe of specimen

systemization

units of common evolutionary dscent define group

phylogenetic species concept

cladistics

taxonomy

categorization based on discrete sets

phenetics

taximetris, classify organisms based on overall similarity, usually in morphology, regardless of their evolutioanry relation

phylogenetics

inference of the evolutionary history and relationships

cladistics

organisms are categorized in groups (clades) based on the most recent common ancestor based on synapomorphic traits

synapmorphy

shared derived characters that distinguish a clade from other clades (shared by members of a monophyletic group)

(sym)plesiomorphy

shared ancestral characters which do not distinguish a clade from other clades (shared by members of a monophyletic group)

does not provide infomation on nested hierachy

e..g 4 limbs for all reptiles

autopomorphy

derived feature unique to taxon

e..g blow hole in all cetaceans

taxon/clade

subset of species that share derived characters (rank)

sister grup

share direct common ancestor

outgroup

phylogenetically close, but not within taxon/clade studiedc

cladogram or evolutionary tree

a branching diagram or tree showing the volutionary relationships among various biological speices or other entities

depicts relationships between different groups and hypothetical common ancestor

monophyletic group - contains

most recent common ancestor of all group members, all descendants

convex: you can trace a path from any member to another without leaving the group

paraphyletic group contaisn

most recent common ancestor (MRCA) of all group members, not all descendants

convex: you can trace a path from any member to another without leaving the group

polyphyletic group, contains

does not contain most recent common ancester of all group members, all descendants

not convex, you cannot trace a path form any member to another without leaving the group, separate phylogenetic origins

evolutionary/phenetic taxonmy

based on similarites

adaptive zone (characteristics based on environment)

phylogenetics/cladistics

only monophyletic groups

synapomorphy

synapomorphy

a characteristics present in an ancestral species and shared exclusively (in more or modified form) by its evolutioanry descendants

describes a derived character

the character is shared by the most recent ancestor

e.g. the presence of the same number of vertebrae in the necks of mammals and giraffes

symplesiomorphy

an ancestral character (trait-state) shared by two or more taxa

describes an ancestral character

the character is shared by the earliest common ancestor

e.g. the presence of a vertebral column in mammals and other vertebrates

analogy

same form and function does not indicate common descent

homopalsy

same function due to convergent evolution, does not indicate common descent

paralell evolution

refers to the independent evolution of similar traits in different but equivalent habitats

occurs in different but equivalent habitats

two distinct species evolve independently, maintaing the same level of similarity

occurs in unrelated or distantly-related species

e.g. evolution of old world moneys and new wolrd monkeys

convergent evolution

refers to the independent evolution of analogous structures in unrelated species

occurs within a particular habitat

two distinct species evolve analogous trait

occur in unrelated species

e.g. devolpemnt of the eye of vetebrates, cephalopods and cnidarian

homology

same organ in differnt organism under every variety of form and function = indication common descent

same ontogenty (developmental history), same genes control the formation of this structure

constructing a phylogenetic tree

use only synapomorphic traits (indication descent)

build using least steps required (parsimony)

outgroup has least shared features

morphological data

characters recognisable, recent adaptations detectable, relatively few characters required

subjective character score

homoplasy

labour intensive, phenotypic plasticitym

olecular data

big datasets, objective information, possibility to choose time scale

no inforamtion about phenotype, variations in mutation (time, chance, duplications), gene-trees

midpoint rooting

assumption, all sequences evolve at same rate

no assumption ancestry, no direction of evolution

outgroop routing

use previous infomration, sequence/species known to be distantly related

infer ancestry; direction of evolution

phylogenetic tree

depicts amount of time between differentiation (genetic distance) of groups

depicts confidence level