lecture 2 systematics, Phylogeny & the tree of life Flashcards
(37 cards)
what is taxonomy
the sciecne of naming and classifying organisms within groups (taxa)
phylogeny
the evolutionary history of a species or group of species ‘tree of life’
systematics
the relationship of determining relationships among organisms
what are the schools of thought in systematics
phenetic system
classic evolutionary system
cladistic system
what is the phenetic system
groups organisms based on phenotype similarity only (how it looks/acts)
most similar traits = most closely related
how reliable is phenetic
unreliable- doesn’t disstinguish between homologous and analogous characters
uncommon but somtimes best option/ first stage
what is the classic evolutionary system
group organisms based on evolutionary relationships.
all shared characterss primitive and derived (accepts mono and paraphyletic groups)
what is the meaning of monophylectic
Monophyletic, or monophylogeny, is a term used to describe a group of organisms that are classified in the same taxon and share a most common recent ancestor. A monophyletic group includes all descendants of that most common recent ancestor.
what is the meaning of paraphylectic
(of a group of organisms) descended from a common evolutionary ancestor or ancestral group, but not including all the descendant groups.
what is the cladistic system
based on similarity of characters that reflect evolutionary relationships
derived characters most important, only accepts monophylectic groups
what is a phylogenetic tree
a graphical representation of evolutionary relationships among a set of organisms or groups
how to interpret a cladogram
node position indicates relative time but branch lengths are arbitrary
how to interpret a phylorgram
branch lengths represent amount of change
how to interpret a dendrogram (ultrametric)
nodes associated with a specific geological time
what are the types of group in phylogenetic trees
ancestor and decendants
ancestor and not all dcendants
missing ancestors (less common)
example of a monophyletic taxon
class mammalia
example of a paraphyletic taxon
class reptillia (becuase birds are not included)
what is a polyphyletic taxon
(of a group of organisms) derived from more than one common evolutionary ancestor or ancestral group and therefore not suitable for placing in the same taxon.
example of a polyphyletic taxon
algae
what is parsimony
Parsimony is the idea that, given a set of possible explanations, the simplest explanation is the most likely to be correct
how do taxonomists use parsimony
to determin which phylogenetic tree (hypothesis) is most likely to be correct; whichever has the fewest evolutionary steps
why are there differences between morphological and genetic similarity
body form changes at a different rate to DNA/RNA
much molecular evolution not expressed in body form
how can time be added to the phylogenetic tree
radiometric dating (isotopes in fossils)
stratigraphy: layering of deposited rocks allows geolgical timescale to be estimated
molecular clocks: amount of genetic divergence used to estimate timing
what are the 6 kingdoms
plantae animalia fungi protista eubacteria archaebacteria
