Week 5: evolutionary history Flashcards
(22 cards)
The evolutionary history of a group of
organisms is called a _________
phylogeny
What is the root of a phylogenetic tree?
Ancestot that gave rise to the rest of the taxa
What is the taxa of a phylogenetic tree?
A species/group at the end of a line
What is the node of a phylogenetic tree?
a point where a branch splits; a hypothetical most
recent ancestor undergoes divergence/speciation
An ________ is a taxon that diverged
before the taxa that are the focus of the
phylogeny and helps to root the tree
outgroup
A _________ is a node that divides into 3
or more branches suggesting that not
enough data were available to resolve
which taxa are most closely related
polytomy
closely related taxa are depicted as ____________ that share a recent common
ancestor
sister groups
A _______ trait is one that is a modified form
of the ancestral trait, found in a descendant
derived
What is cladistic approach?
First method to infer phylogenetic trees, beased on reconstructing relationships between species by identifying synapomorphies (shared derived traits)
What is a synapomorpy?
Traits found in two or more taxa that are
present in their most recent common
ancestor but missing in more distant
ancestors; allow us to recognize monophyletic groups called clades or lineages
A ________________ is an evolutionary unit
that includes an ancestral population and all of its
descendants, but no others
monophyletic group
What are some problems when inferring a tree?
-Traits may be similar due to independent/convergent evolution, not common ancestry
-A reversal in character change may make it seem like no change has occured
-Species may form monophyletic groups based on one traits but part of a different monophyletic group using another trait
__________ states that the most likely explanation or pattern is the one that implies the least amount of change
Parsimony
A phylogenetic tree that is less parsimonious is the tree that scientists tend to go with. What does this mean?
The phylogenetic tree that requires the least amount of changes is the one that follows the principle of parsimony
Wehn tips of branches represent extant taxa, it is not correct to say one taxon is more ________ or ________ than another
primitive, advanced
Taxa at the tips of branches that are closer together are ______________
not necessarily more closely related
A ____________ is the rapid extinction of a large number of diverse organisms around the world
mass extinction
_____________ occur when certain populations are reduced to _____
background extinction, zero
What are 4 causes of background extinction?
normal environment change, emerging disease, predation pressure, competition with other species
Alvarez theory
iridium presence in rock led him to develop theory of meteor that caused the cretaceous-paleogene mass extinction
The largest mass extinction was the ______________ and resulted in the dissapearance of more than 90% of species
end-Permian extinction
What things possibly caused the end-Permian extinction?
Siberian traps added CO2 and SO2 to the atmosphere, caused severe acid rain killing plants and fungi. mercury was released into the atmosphere, oceans became anoxic, sea level dropped dramatically reducing habitat
