BIO Topic 7
What is Systematics
the science of classifing organisms and determining their evolutionary relationships
systematic calssify and determine organisms through what two concepts
Taxaonomy and phylogenetics
what is Taxonomy
naming and classification of organisms
what is phylogenetics
study of evolutionary relationships
what is a phylogenetic tree
a diagramhypothesis that shows how different organisms are related to each other through evolution, based on a scientific analysis of their traits or genetic information.
who created taxonomy
Carl Linnaeus
what does the linnaean system do
groups species in a hierachy of increasingly inclusive categories based on shared characters
what is a taxon in the linnaen system group
a group at any level of the calssifiction hierarchy
example of taxon
species, families, oders, etc..
different taxon are not
necessarily comparable
what is a key aspect of the linnaen system
binomial nomenclature
the genus always has to have a
capital letter
both genus and species named should be...
italicided or if writing, underline it
how did linnaeus build his ranking system
through homologous trait/homolgy
what is homology
similarities due to common ancestry
what is an analohous trait/analogy
similarities that aren't shared form common ancestry but from shared environments ( evolved indipendantly ) ex. flying squirrel and sugar glider
can lose homologous traits shared by relatives?
yes!
grouping by only a few specific shared traits can
not always reflect a true evolutionary history
what is cladistics
the classification of species should reflect evolutionary history (phylogeny)
what is phylogenetics
the study of evolutionary relationships
what are phylogenetic trees
a hypotheis of the evolutionary relationships of a set of species (taxa)
phylogenetics were orginially done with
morphological similarities (usually for fossils)
now Phylogenetics are compare via
molecular sequence like DNA, RNA and proteins, which is much more accurate
phylogenetic trees can be drawn
different ways
no taxa is higher or lower, more or less advanced..
than another
what are extant species
species alive today
all extant species share
a common ancestor that lived over 3 billion years ago
what are LUCA
last universal common ancestor
do extant species and LUCA differ a lot in their evolutionary history
no!
species at the tip of the phylogentic tree do not
have ancestor/descendent relationship but evolutionary relatives
phylogenetic trees can look differnet because o
collapsing or extinct taxa are included/excluded
is not including all species within a taxon good?
no! can be misleading or suggests less diverse taxon
what is relatedness
how recently two taxa share a common ancestor
how can a taxa be more closey related
when they share a more recent common ancestor
relatedeness is not indicated by
the number of nodes between two taxa on a phylogenetic tree
the number of nodes depend on
what other taxa are included, NOT the phylogeny
what is a monophyletic group
a group of organisms that include a common ancestor and ALL of their decendants
what is another word for monophyletic group
a clade
what is a paraphyletic group
a group of organisms that include a common ancestor and SOME but not all of their decendents
What is a polyphyletic group
group of un related organisms that don't include a common ancestor for it's members.
what is cladistics
an approch to systematics where common ancestry is the base for classifying organisms
cladistics uses
homolgies to define clades
what are some implications of cladistics
taxonomy reflects evolutionary history, in phylogenetic studies, organismes should be organised into series of monopheletic groups that relfect shared evolutionary history
how do we find evidence for common ancestry
the study of shared derived characters
definition of shared derived characters
traits that ONLY belong to that specific group, from a common ancestor
can clades me nested within another?
yes!
Phylogenies can be built from
morphological or molecular data
Analogous traits can be
misleading for constucting phylogenies
homologous characters can be divided into what two groups
ancestral charcter and derived character
what is an ancestral character
a trait that was present in the common ancestor of a group of organisms. It’s a "shared" feature passed down to many descendants.
what is derived character
a newer trait that evolved in more recent ancestors and is found in some, but not all, descendants of the common ancestor
phelogenies are infferred by forming
clades based on shared derived characters
what is convergent evolution
indipendant evolutionof similar traits in different lineages
convergent evolution creates
analogies
what is an outgroup
one or more species outside the group of interest ( group of reference)
what is an ingroup
the group of interest
species outside the clade lack the trait therefore
sampling species of an outgroup to an ingroup can infer evolutionary relationships
shared dervived character are
unique to some group and has to have came from a common ancestor where this trait first appeared
systematists compare ingroup species with themselves and outgroup why?
to differentiate between shared derived vs ancestral characteristics, groups species with shared derived characters together which determines which characters derived at various branch points
what is the principle of parsimony
the phelogenetic tree with the least number of evolutionary transitions is most likely.
what types of phylogenetic trees are there
two, cladograms and phylograms
what is a cladogram tree
it shows only the branching pattern with no details, no information about timing or amount of change
what is a phylogram tree
it shows the branching patterns and the branch lengths are proportional to the genetic change or the time of multipule branching points
dating of branching points can be doing by
fossils withing the study of rock layers and layering or a molecular clock
what is a molecular clock
assumes the production of nucleotide per unit of time for a given gene
molecular clocks are calibrated againts
branches whose dates are known from fossils
individual genes vary on
how clock-like they are ( some mutate faster than others )
molecular change should be constante if
evolutionary changes in genes have no effect on fitness
the difference in molecular clock rate for a differnt gene are from
the important of the genes or its parts