Lecture 4: Phylogenetic tree Flashcards
Taxonomy
name and group organisms
* Nomenclature: organizing the naming scheme
* Classification: putting organisms into similar groups
Phylogeny
use the classification of organisms (produced as the result of taxonomy) to deduce their evolutionary relationships
Organisms in the Family Felidae (cats) have ___ claws
retractable
- Members of Felidae keep their claws sharp for hunting by retracting them in their paws
- Other carnivores such as dogs (Family Canidae) use their non-retractable claws as running spikes
Cheetahs have __ claws
blunt, semi-retractable claws used for running
Taxonomy classifies organisms following the principles of ____
Cladistics
Cladistics
an approach for systematics saying that organisms should be classified using ancestral relationship as the primary criteria
Following principles of cladistics how are cheetahs classified
- Cheetah fits the best with other cats when is is classified based on cladistics
- Classification is based on many traits, not just the anatomy of claws
Phylogenetic tree
Branched, tree-like representation of the relationships of organisms
Phylogenetic tree is a ___ of the evolutionary relationship of organisms
hypothesis
True or false: Phylogenetic trees are concrete
- This relationship is NOT CONCRETE
- Classification may change depending on what trait you use/prioritize to build the phylogenetic tree
Branch point
a common ancestor diverges into different species at the branch point
Dichotomy
a branch point where the common ancestor diverges into exactly two lineages
- This is how speciation is believed to occur
Root of the tree
the branch which represent the common ancestor of all taxa in the tree
Sister taxa
group of organisms that share an immediate common ancestor that is not shared by any other group
Sister taxa is a __ concept based on which common ancestor you chose to group the organisms
relative
Basal taxon
lineage that diverges from all other members of the tree early in the history of the group
Property 1 of Phylogenetic Trees
a phylogenetic tree only shows how each organisms are connected to one another
* This is the ONLY information contained in the tree unless otherwise noted
Property 2 of Phylogenetic Trees
The tree shows patterns of descent. This may not always correspond to how similar organisms look or behave.
Property 3 of Phylogenetic Trees
The tree does not infer that a taxon evolved from a neighbouring taxon
*This tree is not suggesting that “Humans evolved from Chimpanzees”, or vice versa
* The common ancestor of Chimpanzees and Humans is a different species from them
A basic phylogenetic tree only shows how each organisms are connected to one another called __
cladograms
Phylograms
Phylogenetic tree which additional information are represented, typically by the lengths of each branch. Branch length may correspond to the amount of genetic change, amount of time, etc
Phylogenetic trees are ___
not set in stone
How is speciation believed to occur?
Dichotomy: a branch point where the common ancestor diverges into exactly two lineages. Perfect tree will have all species resolved by dichotomies.
Polytomy
a speciation event showing a common ancestor diverging into more than two species at once
