Phylogeny Flashcards
phylogenetic tree
model of how a group of organisms descended from a common ancestor
Branch
represents a species
Node
Where a branch diverges into two or more sub-branches.
-where groups split
Polytomy
multiple species appear to diverge at one node
-point where more than 2 branches diverge
Sister taxa
2 taxa that share a common node
Synapomorphy
trait shared by two or more species inherited from common ancestor
-shared, derived characters (evidence 2 taxa related)
Out-group
represents a taxon that diverged earlier from the other taxa in the tree; useful in determining the root of the tree.
monophyletic group
group defined by a single common ancestor
Phenetic
use measures of distance between organisms
- ignores the phylogenetic model of organisms evolving from each other while inferring phylogenies
Cladistic
based on modeling how evolution occurs on the tree
- makes use of the phylogenetic model of organisms evolving from each other to infer phylogenies
basal or ancestral characters
characteristics of the common ancestor
root
beginning of the tree is where the outgroup branches from the group
convergent evolution
Two species may have the same trait because the trait evolved twice independently
secondary loss
An organism may lack a character that its ancestors had
homoplasies
Similarities that are not homologies (not due to common ancestor)
parsimony
with the fewest number of changes necessary (when creating tree)
Derived character
Character not shared by common ancestor of the group
Bacteria
- no nuclei
- mostly small
- most of the micro-organisms you see
Archaea
- no nuclei
- mostly small
- rarer
- live in more extreme environments
Eukarya
large, nucleated cells
Eukaryotes
- sisters with archaea
- Characterized by nuclei and mitochondria
Reuniting can create new species
– Hybridization
– Allopolyploidy
Allopolyploidy
polyploids arising from different species
Habitat bias
Things that live in swampy areas, or underground
Taxonomic bias
Hard things, or hard parts of things
Temporal bias
Things that lived more recently have had less time to be destroyed, or to be buried too deep for recovery
Abundance bias
Things that are more abundant have more chances to be preserved
radiation events
Diversity sometimes arises gradually, and sometimes dramatically
mass extinction events
Species (and families, and bigger groups) sometimes disappear gradually, and some- times dramatically
adaptive radiation
occurs when a single lineage produces many descendant species, in a short period of time, that make their living in a variety of different ways
- Triggered by opportunity, either in the environment, or because of the evolution of the organisms themselves
Ecological opportunity
- An organism arrives in an area with no similar organisms
- A group of competing species is driven extinct (or nearly extinct) by some other cause
Morphological innovation
an organism comes up with a good, new idea
Co-evolution
evolution of one group creates new niches for another group, and vice versa
Hox gene
Hox gene mutations allowed early animals to develop complex body plans
- involved in determining the identity of different body parts
- Taxa with simpler body structures tend to have fewer hox genes
- Evidence that new hox genes were largely created by gene duplication events
Gene duplication
One or more genes may be accidentally duplicated so that the genome has two copies of each gene
- This may make the organism less efficient, and thus be selected against
- may allow for innovation
Tips
represents observed taxa which are the endpoints of the process trying to be modelled
Cladistic vs Phenetic
Cladistic is better
-use phenetic when: only data is distances or dont have enough baseline info
Genetic vs Morphological
Genetic-usually have more info and info easier to measure precisely
-use morph. whe genetic info unavailable
Limitations to phylogenetic tree
- cannot summarize true history of life
- trees constructed by humans not best approx
- our guesses change over time
Intact fossils
retain form
compression fossil
squashed into thin film
cast fossils
occur when decomposing piece replaced by mineral different from surrounding
Permineralized fossil
occur if minerals infiltrate cells as decomposing
