What are nodes?
Branch points on a phylogeny tree that represent common ancestors
What is extant?
moden creatures that still exist today
What are taxa (pl.taxon)
a way to name a group
What is homology?
- "same origin in different organisms under every variety of form and function."
- ex. limb skeleton of various tetrapods share homologous elements
What do homologous structures indicate?
indicate common evolutionary ancestry and are used to generate phylogenetic hypothese of the relationships among organisms
What is analogy?
structures that serve similar function but DO NOT indicate common ancestry
phylogeny based on cladistic methods
- relationships reconstructed based on shared, derived characteristics.
- characters used to define synapomorphies are presumed to be homologous across taxa of interest
- a group defined by synapomorphies.
- ex. Squamata (lizards, snakes, amphisbaenians) all share the Squamata characteristic.
Define monophyletic group
includes ancestor and all descendents
Define paraphyletic group
ancestor and somedescendants
Define polyphyletic group
common ancestor is not included
What do branch points on a phylogeny tree indicate?
speciation events (formation of a new species)
Define allopatric speciation
- the dominant mode of speciation,
- most pervasive.
- when the population separated into two separate groups by a geographic barrier, then reproductive barriers can evolve
Define adaptive radiation
- evoltuion of many diverse species from a common ancestral stock, can result from allopatric speciation.
- typically associated with invasion of areas with unoccupied habitats or "niches"
- evolutionary change in timing of development.
- ex. humans exhibit extended early development and are born at an early age.
- ex2. gills of axolotl are retained throughout its life
- independent evolution of of a similar characteristic (morphology, physiology, ecology, behavior, etc.) in two or more taxa.
- presence of similarity must NOT be due to common ancestry.
- analogy is convergence that has a functional explanation in the biology of the organism.
- ex. wings
What does reduction and loss refer to?
What is reduction
- a reduction in size or prominence of a feature or element.
- ex. humans have relatively simple skull and jaw structure, an example of simplification in a highly derived taxon.
What is reversal
- evolutionary return to a condition seen in an ancestor termed "secondarily derived."
- determined bby analysis within a phylogenetic framework.
- ex. humans are seconadily derived terrestrial.
What is specialization?
- morphological, physiological, and/or behavioral modification for a specialized biological role.
- specializations also sometimes called adapations (determined in phylogenetic framework).
What is parsimony?
When there are multiple hypothesis, the favored hypothesis iswhatever requires the fewest changes or the least explanation