16 pt 2.txt
Card Set Information
16 pt 2.txt
How are synapomorphies and homologies related/
All synapomorphies are homologies but not all homologies are synapomorphies
How is a synapomorphy shared?
Shared because it was derived in the most recent common ancestor
How is a symplesiomorphy shared?
It is shared from a common ancestor but sharing does not necessarily mean close evolutionary relationship
How is a homoplasy shared?
Shared because the same trait originated independently more than once.
What are the traits that are usefull for building phylogenies?
Homologies (synapomorphies and symplesiomorphies) and homoplasies
What is the parsimony principle?
The simplest explanation of observed data is the most reasonable.
What is the maximum likelihood method?
Identifies the tree that most likely produced the observed data
What is the first step in constructing a parsimonious phylogeny?
Selecting the taxa; ingroup and outgroup.
What is the second step in constructing a parsimonious phylogeny?
Selecting data; any trait that is heritable can be used in a phylogenetic analysis.
What are the 4 types of traits used to reconstruct phylogenies?
Morphology, development, behavior, and molecules
What are the pros in using the morphological traits to construct a phylogeny?
Allows for inclusion of extinct species, fossil evidence can help distinguish ancestral from derived traits and date divergences.
What are some cons in using the morphological traits to construct a phylogeny?
Some taxa have few morphological differences, very distantly related species can have too many to differences to actually compare; variation can be caused by the environment
What are some pros to using the developmental traits to construct a phylogeny?
Looking at the development can help explain the relationships between species in which adults differ significantly from one another; and it can also teach about mechanisms of diversification in form.
What is a weaknesses in using the developmental traits to construct a phylogeny?
Developmental mechanisms can be 'reused 'for different functions
What is a pro of using behavioral traits when creating phylogenies?
They can be just as heritable as morphology
What are some weaknesses in using behavioral traits when creating phylogenies?
Some traits are cultural or learned and might have nothing to do with evolutionary relationships; behavior can be plastic which can make measurements difficult.
What are some pros of using molecular data to construct phylogenies?
There are LOTS of characters (base pairs), there is little expertise needed to describe a trait, and rate of change vary among loci in a genome
What is a weakness of using molecular data to construct phylogenies?
There are only 4 possible traits per character so homoplasies are common
What does maximum likely hood do?
Identify the tree that most likely produced the observed DNA data
How do maximum likely hood methods and parsimony methods differ?
Maximum likelihood do not treat all possible evolutionary changes as equally likely or important
What can maximum likelihood modes account for?
Multiple changes at a given sequence position, different likelihood of transitions vs transversions, different rates of change at different positions.
What questions should you ask yourself when constructing a phylogeny tree?
What relationships do each character suggest? What is the ancestral vs. derived state? Which taxa share the derived state?