3 Flashcards
Phylogenies in the circle of the scientific method are?
Hypotheses
Choosing the optimal tree? 2•
•Choose the tree that has the smallest number of character state changes. The tree that gives the smallest number of assumptions of evolutionary processes.
•Choose the tree that is most probable. You can estimate it using models for character evolution.
What do you mean by assumptions in phylogenetic trees?
The addition of a trait is an assumption. Adding multiple of the same traits throughout the tree due to convergent evolution are more assumptions.
Phylogenetic tree is not a depiction of?
Similarity between taxa. Groups closer to each other doesn’t imply that they are more related.
In molecular clocks, branch lengths represent the?
Number of state transitions (e.g. DNA mutations)
Neutral theory of molecular evolution?
Special types of DNA mutations that are disfavoured by natural selection, so they evolve at a neutral rate. These DNA nucleotide substitutions are synonymous mutations. They occur at a normal rate, they can be used to date nodes on a molecular phylogeny.
Cladogram?
Shows branching order or topology only, branch lengths do not mean anything.
Phylogram?
A tree where branching length differ as they reflect the amount of evolutionary change.
Chronogram?
A tree with branch lengths that are calibrated to real time. Nodes indicate estimated ages of ancestors.
If there is a tree without showing a timeline or any representation of time, it is most definitely a?
Cladogram.
In theropods, the pubis bone is pointed?
Anteriorly towards the head.
In ornithischians, the pubis bone is pointed?
Posteriorly, towards the tail.
Symplesiomorphy?
A shared ancestral trait shared by two or more lineages in a larger clade based on the current clade you are looking at.
