Zoo 201 Lec General Terms

Branch points on a phylogeny tree that represent common ancestors

moden creatures that still exist today

a way to name a group

• "same origin in different organisms under every variety of form and function."
• ex. limb skeleton of various tetrapods share homologous elements

indicate common evolutionary ancestry and are used to generate phylogenetic hypothese of the relationships among organisms

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.

includes ancestor and all descendents

ancestor and somedescendants

common ancestor is not included

speciation events (formation of a new species)

• the dominant mode of speciation,
• most pervasive.
• when the population separated into two separate groups by a geographic barrier, then reproductive barriers can evolve

• 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

morphology

• 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.

• 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.

• morphological, physiological, and/or behavioral modification for a specialized biological role.
• specializations also sometimes called adapations (determined in phylogenetic framework).

When there are multiple hypothesis, the favored hypothesis iswhatever requires the fewest changes or the least explanation