Phylogenetics Flashcards
Phylogenetic Tree
Phylogenetic Tree: Hypothesis of evolutionary relationships among different organisms based upon shared morphological, behavioral, biochemical, and genetic characters
Branches illustrate how different taxa diverged from CA over time
B/c all living organisms related, any 2 taxa always share CA = expect taxa to share traits inherited from CA (more recent CA = more traits expected to be shared)
Taxon (Taxa)
Taxon (plural: taxa): Group of one or more organisms classified as unit
Can be at any hierarchical level (species, genus, family)
Each taxon typically defined by shared characteristics that distinguish it from other groups
Homologous
Homologous: Traits or structures that share common ancestry, even if their functions differ
Example: forelimbs of mammals, birds, and reptiles are homologous structures, despite their varied functions
Convergent
Convergent: Traits or structures that arise independently in different species due to similar environmental pressures, leading to similar adaptations
Example: wings of bats and birds, which evolved independently for flight
Morphology
Morphology: Study of form and structure of organisms, including their external features and internal organization
Helps classify organisms and understand their evolutionary relationships
Phenotype
Observable physical and physiological traits of organism, resulting from interaction between its genotype and its environment
Example: Colour, size, and shape
Character
Character: Specific trait or feature of organism that can be measured or observed
Example: Number of petals in flower or presence of certain type of leaf
Character State
Character State: Specific condition of character at particular point in time
Example: “Flower colour” can have different states like “red,” “blue,” or “yellow”
Shared Character
Shared Character: Trait that’s present in two or more taxa
Can be used to infer evolutionary relationships and create phylogenetic trees
Ancestral (Plesiomorphic)
Ancestral (Plesiomorphic): Character state that’s present in common ancestor and retained by its descendants
These traits considered primitive and may not provide much information about more recent evolutionary relationships
Derived (Apomorphic)
Derived (Apomorphic): Character state that’s evolved more recently in lineage, distinguishing it from its ancestors
Derived traits crucial for identifying evolutionary relationships
Synapomorphy (Shared Derived Character State)
Synapomorphy (Shared Derived Character State): Derived character that’s shared by two or more taxa and used as evidence of their common ancestry
Synapomorphies important for defining clades in phylogenetic tree
Symplesiomorphy (Shared Ancestral Character State)
Symplesiomorphy (Shared Ancestral Character State): Character that’s shared by multiple taxa but not useful for inferring evolutionary relationships because = ancestral trait
Can be present in wide range of descendants, leading to ambiguity in classification
Ingroup
Ingroup: Group of taxa being studied or analyzed in phylogenetic analysis
Contrasted with outgroup to help determine evolutionary relationships
Outgroup
Outgroup: Taxon or group of taxa that’s outside ingroup but closely related to it
Used as reference point to help determine direction of character evolution and to identify derived traits
