Phylogenetics Flashcards
What is microevolution?
Changes in allele frequencies within a population over generations
Involves a single species
What is macroevolution?
Evolutionary changes that result in different species (speciation), or higher taxa such as, family, order, phylum, etc.
What does a longer divergence time mean?
More time for independent evolutionary change and more time to accumulate differences
What is an inference made about relation of species?
More closely related species will share more similar characteristics than less closely related species because they share more evolutionary history
What is phylogenetics?
The study of evolutionary history and the relatedness of of groups
To consider hypotheses about evolutionary relatedness between groups, you need to be able to (2 things):
- Understand how to read a phylogenetic tree
- Apply this information to build a tree using data on shared characteristics
How does time move on a phylogenetic tree?
From the base of the tree (older) to the tips of the tree (newer)
What does the base of a phylogenetic tree represent?
The shared ancestor of all species on the tree
What do the nodes of a phylogenetic tree represent?
The common ancestors that all the species that branch off of it diverged from
How are species with more recent common ancestors related?
They are more closely related because they have had less time to accumulate genetic differences from each other
How can you determine relatedness of species?
By comparing most recent common ancestors
What is synapomorphy?
Shared, derived characteristics that result from a common ancestor
What is homology?
Similarity resulting from common ancestry
More closely related taxa will share more what?
Character states
What are character states?
Different forms of the characteristic
What is an outgroup?
A group with characteristics that are ancestral to the group of interest (ingroup)
If the ingroup species have different character states for a characteristic, the character state must be what?
A new evolutionary feature for the group
What are the two characteristics of synapomorphies?
- Shared, derived character states that indicate homology
- More closely related groups will share more synapomorphies
What is plesiomorphy?
Character states found in the ancestor of the group (the outgroup has plesiomorphies
What is apomorphy?
Derived character states found in descendants of the group
Evolutionary novelties acquired after divergence from the ancestral group
When building a phylogenetic tree, what should be used to build relationships?
Hierarchical classification and synapomorphies
What is a monophyletic group?
A common ancestor and all of its descendants
The only valid evolutionary group
What is a clade?
A monophyletic group
Why does monophyletic grouping make sense? 2 reasons.
- Defined by shared, derived characteristics
- Can’t randomly exclude descendants
What is a paraphyletic group?
A group containing a common ancestor, but not all of its descendants
What is homoplasy?
An evolutionarily invalid grouping by character states that appear the same in 2 taxa but have not evolved from a common ancestor
Homoplasy is a result from what?
Convergent evolution
What is convergent evolution?
Independent evolution of the same character state in multiple, separate lineages
What is a polyphyletic group?
An evolutionarily invalid grouping: a group characterizes by 1 or more homoplasies
What is parsimony?
“The simplest explanation is the best”
Best phylogenetic tree is the tree with the fewest evolutionary steps
