Lab Manual Ch. 5 Flashcards
phylogenetic systematics
- method for reconstructing evolutionary relationships
- clusters organisms into groups based on modified characters that are shared by members of the group
3 characteristics of the method of phylogenetic systematics
quantitative (characters can be enumerated), reproducible (data are not subjective), and testable
assumptions of phylogenetic systematics
- evolution occurs
- there is a singly phylogeny of life, a result of evolutionary descent
- characters are passed from generation to generation, modified or unmodified, during evolutionary descent
steps in constructing a phylogenetic tree
- identify homologous characters
- code the characters as ancestral or derived and construct a matrix
- group by shared derived characters to produce a phylogenetic hypothesis
character
observable trait of an organism
character reversal
a form of homoplasy, where a species re-evolves the ancestral character state
unique vs shared derived character
unique - found in one taxon
shared - found in more than one taxon
it is —— —— —– that are used to infer evolutionary relationships
shared derived characters
binary vs multistate characters
binary: present or absent (coded 0 and 1)
multistate: in more than two different states (coded as 0, 1, 2)
multistate characters can be considered to be
ordered or unordered
ordered characters
follow a logical evolutionary path (eg small size beak to medium to large)
unordered characters
do not follow any logical evolutionary progression (eg colour of coral reef fishes)
go through the process of making a phylogenetic tree
parsimony
a principle in phylogenetic which forces one to accept the shortest tree that explains all the character states
polytomy
an unresolved group of three or more taxa
