CH 21 (Ch 3) Flashcards
Phylogeny
a description of the evolutionary history of relationships among organisms (or their parts)
Phylogenetic tree
diagram that portrays a reconstruction of history (species, populations or genes). Can trace evolutionary histories
x axis is always time
root
earliest common ancestor
start point of phylogenetic tree
Taxon
any group of species that has been designated or named (humans, primates, mammals)
clade
any taxon that consists of all the evolutionary descendants of a common ancestor
node to newest species you are looking at
Sister species
two species that each other’s closest relatives
Sister clades
two clades that are each other’s closest relatives
Homologous trait
- any feature shared by two or more species that has been inherited from a common ancestor
ex. DNA sequences, protein structures, anatomical structures, behavior patterns
Derived trait
ancestor whose descendent that has evolved or adapted a new trait that was from the ancestor
Arise due to a selective pressure
Ancestral trait
has undergone little change from ancestral trait
Synaptomorphies
derived traits that are shared among a group of organisms
Evidence of a common ancestry
Vertebral column is a synaptomorphy of all vertebrates
Convergent evolution
independently evolved traits subjected to similar selection pressures become superficially similar
- don’t share a common ancestor
usually traits are different like wings, bats are skin and birds are made of feathers
Evolutionary reversal
characteristic from a derived state back to an ancestral state
traits appear that appear and then disappear due to some selection pressure
Generate homoplasies
the traits developed through Convergent or Evolutionary reversal that are similar for reasons other than a common ancestor
Not indicative of common ancestor, just common evolutionary paths
see the tree diagrams for in-group and outgrip terms
!!!
Parsimony principle to explain how phylogenetic trees are made
the preferred explanation of observed data is the simplest explanation
Minimize number of evolutionary events assumed
“the best explanation is the one that fits the data best while making the fewest assumptions”
Morphology (source to make the tree)
the presence, size, shape, or other attributes of a body part
Important source of phylogenetic information
Limits: some taxa exibit very little morphological differences despite great species diversity
There are very few morphological traits that can be compared between very
distant species
Development (source to make the tree)
similarities in developmental patterns reveal evolutionary relationships
Early developmental similarities may be lost during later development (notochord)
paleontology (source to make the tree)
fossil record as a source of evolutionary history
When and where species lifed, what they looked like
Evidence for extinct species
Limits: few or no fossils may be present for groups of animals, info may be fragmented
Only fossils that are preserved can be seen
behavior (source to make the tree)
- behavioural traits like bird songs Can’t be tracked as they are learned, while frog calls are genetically programmed
Molecular data (source to make the tree)
heritable variation that is encoded in DNA
Comparing DNA sequences
limit is that we don’t have all data on all mutations
how do biologists use phylogenetic trees?
help reconstruct the past, compare and contrast organisms and predict the future (IE new flu vaccine)
binomial nomenclature
Kingdom - Phylum - Class - Order - Family - Genus - Species
“keep pushing cookies or fail girl scouts”
monophyletic
taxa in biological classifications are expected to be this
- contain an ancestor and all descendants of that ancestor only
polyphyletic group
no common ancestor is considered, just comparing branches/species on the tree (black dotted box)
paraphyletic:
some descendants are examined but not all (red circles). A group that does not include every descendent.
