lab 5 Flashcards
what is convergent evolution
two distantly related species which share same evolved traits
what is phylogeny?
phylogeny is used to classify organisms into natural groups and can also be used to classify zoonotic disease transmission
what are systematics?
study of organism diversity
how are systematics and taxonomy related?
both attempt to arrange groups according to evolutionary relationships
what are phylogenetic systematics?
reconstructs and implies relationships among groups of organisms that are derived from a common ancestor
evolutionary relationships are inferred from characters which are observable
clusters organisms into groups based on modified characters to produce a hypothesis of evolutionary relationships and classification of the relationships
how can phylogentic systematics be made more reliable?
classifications which use many characters are more informative in determining true evolutionary relationships
why are phylogenetic systematics good for studying things?
the system is quantitative, producible, testable by scientific method
what do phylogenetic systematics assume?
evolution occurs and that there is a single phylogeny of life which everything descended from
characters are passed from gen to gen both modified and not during evolution descent
what does descent w/ modification mean and how can it be observed?
descent w/ modification means a genaology (ancestor and descendants) go through a change in characterisitcs or attribute
this relationship can’t be directly observed, but characteristics which stem from it can be observed and so phylogenetic trees are used to present hypothesis for these relationships via observing characters
how do characters change over time and what does this mean?
not all characters change at the same rate so organisms will be a combination of ancestral (unmodified) and derived (modified)
what are unique derived characters?
character possesed by only one taxa
what are shared derived characters and why are they important?
shared derived character states are the ones used to reconstruct evolutionary relationships, the phylogeny of taxa and are used to construct phylogenetic trees
what are the steps to constructing a phylogenetic tree?
- identify homologous characters
- code characters as ancestral or derived + constructed
- group shared derived characters to created a phylogenetic hypothesis
what is a character?
an observable trait of an organisms can be morphological, molecular, developmental, physiological, behavioural, ecological
what are homologous characters?
haracters in 2+ species which are dervied from the same structure in a common ancestor
w/o contrary evidence how are common characteristics assumed to arise?
not all resemblances come from a common ancestry (convergent evolution), however, in absence of contrary evidence shared characters are always assumed
what is homoplasy?
homoplasy is when characters evolve more than once, which means the character occurs in 2+ species but not in the most recent common ancestor
what is character reversal?
character reversal is when species reevolves ancestral character state
how are characters coded on a phylogeny tree?
binary which are coded 0, 1 or multistate which are coded 0, 1, 2 etc. this doesn’t mean a sequence of changed but that there’s multiple derived states
what are the two types of multisate characters and which is the default?
the multistate characters can also be ordered which follow logical evolutionary paths (small beak→ medium beak → big beak) or unordered which doesn’t follow a logical progression (colours of coral reef fish which all evolve independently from each other/dont follow a precise sequence)
usually multistate characters are assumed unordered since their evolutionary transformation are generally unkown
what are caldograms?
caldograms are another name for phylogenetic tree
what is a character transformation?
character transformation is modification of a character state
what is a character state?
character state is 1+ alternative forms of the same character
what is an outgroup?
outgroup is a taxon which is usually a sister group of studied group and is used to determine which two homologous character states maybe be derived
what is outgroup comparison?
outgroup comparison is the method to determine which of two homologous character state is ancestral or derived
how can ancestral and derived traits be differentiated?
characters found in both outgroup and ingroup are ancestral, those found in only ingroup are derived
what is parsimony?
parsimony is the principle in phylogenetics which forces the shortest tree which explains all character sates to be accepted
what is principle of parsimony?
principle of parsimony is used to determine which tree bests fits data during phylogenetic analysis as its possible to build more than one tree for one set of character
shortest tree to a trait is always best
what is the optimal tree?
optimal tree minimizes number of homoplasious character/required least number of character state transoformation and is known as the shortest tree
