taxonomy and phylogeny

  • taxonomy= study of classification of organisms which puts them into groups reflecting phylogeny

  • systematics= organises diversity of living things in an evolutionary context

  • taxon= taxonomic unit to which organisms are assigned

  • each species has a unique identifier

  • biodiversity & conservation= tells us which species are important

  • disease and pests= helps identify and treat diseases

  • food= helps us identify toxic foods

classification system

  • made by carolus linnaeus

  • system of grouping hiercharchal groupings

  • not really any meaning

  • species= group in interbreeding natural populations reproducing to produce fertile offspring isolate from other such groups

  • species ranking problem due to ring species (impenetrable barrier forms around so they can’t leave)

  • linnean system= gives organisms 2 part names (genus+species) and shows the same information as a phylogenetic tree

Domain

Kingdom

Phylum

Class

Order

Family

Genus

Species

  • traditionally phylogeny was worked out using morpholgical features but today molecular data is used (e.g. DNA, RNA, protein sequence)

  • if taxonomies are systematic than classification should follow phylogeny perfectly

  • phylogenetic trees are a representation of evolutionary relationships with the root being the oldest common ancestor

  • phylogenetic trees only reliable if there is a 70+% confidence in the branch

  • clades in phylogenetic trees should be monophyletic to be valid

  • monophyletic clade= ancestral species and all of its descendants

  • paraphyletic clade= ancestral species but not all of its descendants, use discouraged as not valid but unavoidable

  • polyphyletic clade= group of organism which lack a common ancestor

  • clades= groups that share derived characteristics

  • characters= cladistic approach= phylogenies inferred by comparing organismal features that vary within species, have to be homologous

  • homology= feature inherited directly from a common ancestor

  • homoplasy= features evolved independantly in different lines due to parallel or convergent evolution, misleading information

  • synaomorphies= new feature unique to a particular group shared by all members of the clade

  • symplesiomorphies=primitive ancestral characters shared by multiple clades