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How are synapomorphies and homologies related/
All synapomorphies are homologies but not all homologies are synapomorphies
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How is a synapomorphy shared?
Shared because it was derived in the most recent common ancestor
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How is a symplesiomorphy shared?
It is shared from a common ancestor but sharing does not necessarily mean close evolutionary relationship
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How is a homoplasy shared?
Shared because the same trait originated independently more than once.
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What are the traits that are usefull for building phylogenies?
Homologies (synapomorphies and symplesiomorphies) and homoplasies
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What is the parsimony principle?
The simplest explanation of observed data is the most reasonable.
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What is the maximum likelihood method?
Identifies the tree that most likely produced the observed data
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What is the first step in constructing a parsimonious phylogeny?
Selecting the taxa; ingroup and outgroup.
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What is the second step in constructing a parsimonious phylogeny?
Selecting data; any trait that is heritable can be used in a phylogenetic analysis.
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What are the 4 types of traits used to reconstruct phylogenies?
Morphology, development, behavior, and molecules
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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.
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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
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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.
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What is a weaknesses in using the developmental traits to construct a phylogeny?
Developmental mechanisms can be 'reused 'for different functions
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What is a pro of using behavioral traits when creating phylogenies?
They can be just as heritable as morphology
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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.
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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
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What is a weakness of using molecular data to construct phylogenies?
There are only 4 possible traits per character so homoplasies are common
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What does maximum likely hood do?
Identify the tree that most likely produced the observed DNA data
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How do maximum likely hood methods and parsimony methods differ?
Maximum likelihood do not treat all possible evolutionary changes as equally likely or important
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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.
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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?
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