PHYLOGENETICS supplementary material Flashcards
a representation of how different types of
organisms are related, and often looks something
like a family tree (
phylogeny
they study what the organisms (or fossils, in some cases)
look like, what their patterns of development are,
and (more recently) their DNA sequences.
evolutionary biologist
it occurs when a new species was fromed whihc was different from the species below the tree
speciation
both species arising
from a branch point evolve so that they are different
from their common ancestor.
speciation
commonly used method for constructing a
phylogeny is called
cladistics
specifically refers to a group of organisms and their
common ancestor(s).
“clade”
is based on looking at changes between
ancestors and modern species
Cladistic
a group of organisms that is somewhat, but not too closely related to the organisms you want to study;
outgroup
(commonly referred to as characters in the context of phylogenetics)
characteristics
refer to character states that
differ from the ancestral forms
derived
character states as “primitive”
ancestral
creates phylogenies by grouping
organisms that have the same derived character
states
cladistics
it is when the character states close to
each other on the tree.
shared derived
If all character states just
changed once in evolutionary history
shared derived character
two types of events which
can muck up reconstruction of a true phylogeny
- convergence
- reversal
it is the same derived character state
evolving twice, independently
convergence
it is he possession of the ancestral character
state by an organism whose ancestor actually
had the derived character state
reversal
these two can obscure the true
phylogeny
convergence anf reversal
in —— we make the assumption that they
are relatively uncommon.
cladistics
they are rare, will still occur
convergence and reversals
developing a phylogeny, and by avoiding
characters which we know include ———— or ———–
reversals or convergence
it helps to select the best tree
parsimony
the notion that a simpler explanation for something is more likely to be correct than a more complicated explanation
Parsimony
the idea that the simplest
tree, requiring the fewest changes in character state
(ancestral to derived or derived to ancestral) is most
likely to be the correct tree
parsimony
a character state would
have to arise multiple times.
bipedal
literally involves counting the number of changes
required for each possible tree, and identifying the tree with the fewest changes.
parsimonious tree
it helps analyze possible trees; indicate the presence of state changes with hash marks.
character matrix
how to help determine the most parsomonious tree?
find the tree with the smallest number of changes
