Chapter 23 Flashcards
In phylogenetic trees, the point where a branch splits, representing the common ancestor from which the descendant species diverged. In plants, the point on a shoot where one or more leaves are attached.
Node
A diagrammed hypothesis about the evolutionary history, or phylogeny, of a species.
phylogenetic tree
Groups that are more closely related to each other than either of them is to any other group.
sister groups
All the species in a taxonomic entity such as family or genus.
Taxon
Describes groupings in which all members share a single common ancestor not shared with any other species or group of species.
monophyletic
Describes groupings that include some, but not all, the descendants of a common ancestor.
paraphyletic
Describes groupings that do not include the last common ancestor of all members.
polyphyletic
In the discipline of systematics, an anatomical, physiological, or molecular feature of an organism that varies among closely related species.
character
The observed condition of a character, such as presence or absence of lungs or arrangement of petals.
character state
Describes characters that are similar in different species because of descent from a common ancestor.
homologous
Describes similar characters that evolved independently in different organisms as a result of adaptation to similar environments.
analogous
A shared derived character; a homology shared by some, but not all, members of a group.
synapomorphy
Phylogenetic reconstruction on the basis of shared evolutionary changes in characters, often called synapomorphies.
cladistics
A track or trail, such as a dinosaur track or the feeding trails of snails and trilobites, left by an animal as it moves about or burrows into sediments.
Trace Fossil
Sterols, bacterial lipids, and some pigment molecules, which are relatively resistant to decomposition, that accumulate in sedimentary rocks and document organisms that rarely form conventional fossils.
Molecular fossils
A sedimentary rock formation in British Columbia, Canada, that preserves a remarkable sampling of marine life during the initial diversification of animals.
burgess shale
A sedimentary rock formation in Germany, preserving fossils that document fish, birds, mammals, and reptiles from the beginning of the age of mammals.
messel shale
The series of time divisions that mark Earth’s long history.
geologic timescale
Dating by using the decay of radioisotopes as a yardstick, including (for time intervals up to a few tens of thousands of years) the decay of radioactive 14C to nitrogen and (for most of Earth history) the decay of radioactive uranium to lead.
radiometric dating
The time it takes for an amount of a substance to reach half its original value. Radioactive half-life is the time it takes for half of the atoms in a given sample of a substance to decay.
half-life
A catastrophic drop in recorded diversity, which has occurred five or more times in the past 541 million years.
mass extinction
