Lecture 4 (phylogeny) Flashcards
Define a taxonomy and describe its similarity and difference with systematics
Taxonomy:
-Classifying species based on similarities and differences
-Quite generalized
-Does not explain evolutionary relationships
Systematics:
-Explains evolutionary relationships based on phylogeny (cladistics and phylogenetics)
-Organizes biological diversity and explains evolutionary events like speciation
Explain what a phylogenetic tree is
-Shows evolutionary relationships with ancestors and descendants
-Consists of a root, basal taxon, nodes, sister taxa, polytomies, and tips
-Created via homologous traits, morphological and molecular data
-They are hypotheses so they’re tested and repeatedly modified
-Strongest evidence is by looking at common ancestry
Explain what morphological data is
-Compares size, shape, # of bones, and anatomical similarities and differences
-For extinct and extant species
Explain what molecular data is
-Compares DNA, RNA, and Nucleic acids to recognize similar characteristics amongst species that cannot be determined by morphological data
-Helped determine three main domains and therefore affected taxonomic classifications
-For extant species
Define the following terms that are involved in phylogenetic trees
Taxa: individual organisms, species, or a group of species
Node: A branch point that depicts a common ancestor; can be rotated as it does not change relationship; do not count nodes
Sister Taxa: Two (or more ?? ask) taxa that share a common ancestor and are closely related
Basal Taxon: A species that diverged from the tree early on; its most recent ancestor is the root (Ask if this is always true)
Speciation: Evolutionary event; divergence from a common ancestor; more complex shared characteristics are, the more closely related
Root (ancestral lineage):The common ancestor for all taxons in the phylogenetic tree
Polytomy: When there are 3+ species stemming from a single common ancestor
Tips: Also known as the descendant taxa; represents a group of taxa (a clade) or a taxon
Lineage: Path of evolution for an ancestor and its descendants
What does branching tell you in phylogenetic trees
-The amount of time that has passed before speciation occurred
- The amount of evolutionary changes that occurred
DO NOT COUNT NODES AS THEY DON’T DEPICT THE ORDER IN WHICH THE SPECIES APPEARED UNLESS THEY FOLLOW THE SAME PATH
-The further away taxa are at the tips, the larger the changes that they underwent; sister taxa undergo minimal changes
-The trees don’t show evolutionary advancement in terms of placement as this idea does not exist
How do polytomies arise
-Lack of knowledge; further research is made (collection of morphological and molecular data) until a differentiation can be made
-Rapid speciation occurred which led to minimal changes amongst taxa
Which method is the most ideal to track evolutionary relationships: Morphological data, molecular data, or both
-Individually, molecular as it shows relatedness that cannot be seen by naked eye
-But ideally both methods are used
How does taxonomy and phylogeny (cladistics) relate
-All clades are taxa but not all taxa are clades
-Shows that there is an inconsistency in taxonomy
-Why phylogeny is more accurate in comparing species
Define homology
-Similar characteristics stem from common ancestor
-Phylogenetic trees are built off of homologous traits
-Shared characteristics tend to be more complex as it proves that there are close similarities in molecular and morphological data which is where the importance of complexity comes from
Define analogy and homoplasy
-Shared characteristics are not derived from same ancestor
-Traits evolved independently
-Arrived due to similar environmental conditions
-Species are not closely related
-Shared characteristics are very simple
Homoplasy is another term for an analogous structure.
What is convergent evolution
-Independant evolution of similar traits in different lineages
Define an ingroup and its relation to an outgroup
Ingroup: the group of taxa that you want to study
Outgroup: One or more taxa that is related to the ingroup by diverged early on
What are characters
-Anatomical, physiological, or molecular features of organisms
-Character states are the presence or absence of characteristics
Shared derived character vs. Shared ancestral character
Shared derived characteristics (Synapomorphy):
-A shared trait between two or more taxa and their most recent common ancestor but is not found in the ancestor that precedes the clade
Shared ancestral character (symplesiomorphy):
-A shared trait between two or more taxa including the preceding ancestor of the clade
Define apomorphy and which term it is correlated to
-A derived character
-Correlated with synapomorphy
Define Plesiomorphy and its relation to symplesiomorphy
-An ancestral character
-Correlated with symplesiomorphy
Define a clade and a nested hierarchy
-Consists of an ancestor and its descendants
-All clades are taxa but not all taxa are clades due to the lack of specification and accuracy in relation w.r.t. evolution
-A nested hierarchy explains how clades can grow in size as you include more ancestors and all their ancestors
How are clades simplified
If you have a clade that has a number of descendants of the same ancestor, it can be collapsed into showing just the common ancestor
How do cladograms compare and differ to phylogenetic trees
Similarities:
-Both depict evolutionary changes
Differences:
-Cladograms only show the evolutionary relationships; branch length holds no significance
What is cladistics
-Looking at homologous characteristics (phylogeny) to understand evolutionary relationships
Define monophyletic
-Also known as a clade
-Consists of an ancestor taxon, all its descendants, and no unrelated taxa
Define paraphyletic
-Consists of an ancestral taxon but not all of its descendants
Define polyphyletic and how its derived
-Includes distantly related taxa (shared ancestor but not recent), but does not include most common ancestor for entire group
-Incorrect taxonomic classification (can be easily fixed but stemmed from forming tree via generalized similarities and not specific similarities)
-The group is missing common ancestor that unites them all (missing fossil records)
-Have more than one common ancestor due to speciation
