Ch.26 - Phylogeny and Tree of Life Flashcards
Goals of chapter 26:
Become familiar w vocab relating to systematics and phylogenetics.
Correctly interpret relationships shown on phylo trees.
Have a basic understanding of how phylo trees:
- are constructed using parsimony
- can be used to test hypotheses
Goals of chapter 26:
Become familiar w vocab relating to systematics and phylogenetics.
Correctly interpret relationships shown on phylo trees.
Have a basic understanding of how phylo trees:
- are constructed using parsimony
- can be used to test hypotheses
Which field of biology is devoted to the ordered division and naming of organisms
Taxonomy: a field of biology devoted to the ordered division and naming of organisms
___________ is a field of biology focused on determining evolutionary relationships among different groups.
Systematics: a field of biology focused on determining evolutionary relationships among diff groups.
- Use data fr fossils, genes, and behavior to infer evol relationships
- Illustrate relations in branching phylogenetic trees.
What is phylogenetics?
Phylogenetics: a method for det evol relationships
- Phylogeny: evolutionary history of a species or group of species
A phylogenetic tree represents a hypothesis about ______________.
A phylogenetic tree represents a hypothesis about evolutionary relationships.
What does each branch in a phylo tree rep?
Each branch point represents the split of two species
_________ are groups that share an immediate common ancestor
Sister taxa are groups that share an immediate common ancestor
I.e. share a unique common ancestor not shared by any other groups.
What is meant by a rooted tree? Polytomy?
Rooted tree: has branch representing the last common ancestor of all taxa in the tree.
Polytomy is a branch from which more than two groups emerge
T/F: phylo trees show patterns of descent and indicate absolute age.
FALSE
Phylo trees DO show patterns of descent
Phylo trees DO NOT indicate absolute age
It shouldn’t be assumed that a taxon evolved from the taxon next to it
Describe how to create a phylogenetic tree
Gather data on groups of interest:
- Morphology, genes, biochem, behavior
- Use only traits that result fr common ancestry (homologies)
- Avoid traits that are result of convergent evolution (analogous traits)
Analogous structures or molecular sequences that evolved independently are also called _________
Analogous strucs or molecular seqs that evolved indep are also called homoplasies
- Result of convergent evol, NOT common ancestry.
How might fossil evidence and degree of complexity be used to distinguish homologous structures from analagous/homoplasies?
The more complex two similar structures are, the more likely it is that they are homologous
What is a clade?
Clade: group of species wh incl a common ancestor and all species that descended from that ancestor
Aka monophyletic groups
Can be nested w/i larger clades
What is contained w/i a paraphyletic group?
Paraphyletic group contains a common ancestor and some, BUT NOT ALL, of its descendents
What differentiates a polyphyletic group from a mono- or paraphyletic group?
Polyphyletic group: includes taxa with a different common ancestor
Differentiate shared ancestral vs shared derived traits.
Shared ancestral: character that originated in common ancestor of a taxon
- All members of the taxon have that trait
- Ex: all vertebrates (incl mammals) have a backbone
Shared derived: an evolutionary novelty unique to a partic clade
- Ex: w/i vertebrates, only mammals have hair
Describe how to infer phylogenies (evol relationships)
Ask: in wh clade did a shared derived character first arise?
Make table listing shared derived traits
- For ea group of interest, note whether character is present (1) or absent (0)
Include an outgroup: group known to have diverged fr evol lineage before any groups of interest.
Most common trait reps first branch point on phylo tree → repeated for next most common trait.
What is the principle of max parsimony?
Investigate the simplest explanation that is consistent with the facts
Most parsimonious tree reqs fewest evol events:
- Simplest pattern of morphological changes
- Fewest # of DNA base changes
- Utilizes computer programs
Principle of Maximum Likelihood
Some DNA base changes are more likely than others
Explain why phylogenetic trees are considered relative and not absolute.
Can det wh traits occurred earlier and wh occurred later relative to other trait
Length of a branch reflects _____________
Length of a branch reflects number of genetic changes
May also rep time—det by fossil record. Always check if indicated.
______________ allows us to predict features of an ancestor from features of its descendents
Phylogenetic bracketing allows us to predict features of an ancestor from features of its descendents
- “In-reverse” inference
- E.g. used to infer features of dinosaurs from their descendents (birds and crocodiles)
T/F: The animal kingdom in monophyletic
TRUE
The animal kingdom in monophyletic
Given a phylogenetic tree, describe how to det:
- Closest relatives
- Sister groups
- Clade/monophyletic groups
Given a phylogenetic tree, describe how to det:
- Closest relatives - anything conn to shared node
- Sister groups
- Clade/monophyletic groups - includes node
- Sister taxa
- common ancestor
- taxon closely related
Each branch tip on a phylogenetic tree represents a specific group of organisms known as a(n) _______
Each branch tip on a phylogenetic tree represents a specific group of organisms known as a taxon.
