Theme 5AB Flashcards
What is a phylogeny
History of descent with branching
Shown as phylogenetic trees/phylogenies
What does a branching diagram tell us
Shows relationships between species often according to time since a common ancestor
What do the tips, branches, node and root tell us on a phylogenetic tree
Tips: terminal node
Branches: new species
Node: point where a branch splits, represents a common ancestor from which the descendant species emerge
Root: common ancestor population
What are sister groups
Two species that share a common ancestor not shared with any other species or groups
What hypothesis do phylogenies provide
Hypothesis of evolutionary relationships
What is a phylogram
Tree where the branch lengths represent evolutionary change/time
What is a cladogram
Tree where the branch lengths are all the same (no time)
How can you use morphological data to infer phylogenies
Use “characters” shared among organisms (vary among, but not within species)and have a genetic basis
What is considered to be the “best” phylogenetic tree
The one with the fewest number of changes required
How can DNA data be used to infer phylogenies
Each nucleotide in a sequence can act as a trait underlying logic of phylogenetic inference is identical for morphological and molecular characters
DNA sequence differences represent time since common ancestor
What is a monophyletic group
Includes a common ancestor and all of its descendants
What is a paraphyletic group
Included a common ancestor and some but not all of its descendants
What is a polyphyletic group
Does not include common ancestor
What is adaptive radiation
The rapid evolution of new species occupying new niches
What is anagenesis
Speciation where the ancestor species is wholly replaced by a new species (evolution within lineage)
What is cladogenesis
Parent species splits into two species
What is graduated evolution
Slow and steady gradual evolution (results in anagenesis)
What is punctuated evolution
Rare and rapid events of branching speciation (results in cladogenesis)
What is the difference between morphological, chromosomal and molecular characters
Morphological: observable traits (wing patterns)
Chromosomal (number of chromosomes)
Molecular: DNA sequences
Homologous verses analogous characters
Homologous: shares a common ancestor
Analogous: similarity in appearance but not origin
What is the outgroup
Belonging to similar class of animals
What is the principle of parsimony
Not willing to spend resources unnecessarily
What does it mean if all the animals on a phylogenetic tree have tips at the same length
All the species still exist (not extinct)
How does phylogeny relate to taxonomy
Member of these groups (like genus) are assumed to share a more recent common ancestor with each other then members of other groups
What is macro evolution
Evolution above the species level, assess the diversity of an entire Claude and its position on the tree
What is a clade
A group of organisms believed to have evolved from a common ancestor
What is convergent evolution
Evolution of similar adaptations in distantly related organisms that occupy similar environments
What are the drawbacks to using molecular characters for phylogenetic trees
There are only 4 alternate character states that exist at each position in a DNA or RNA sequence
Only 20 alternate character states at each position in a protein
This makes it difficult to asses the homology of a nucleotide base substitution that appears at the same position in the DNA of 2+ species
What are the 2 character states
1) ancestral character states: original state
2) derived character state: newer state
What is the difference between apomorphy and synapomorphy
Anapomorphy: derived character state
Synapomorphy: derived character state found in 2+ organisms
