Campbell Biology Chapter 25

Eras

The boundaries of the geological time.

Precambrian

4,600-540 million years ago

Paleozoic

543-245 million years ago, Cambrian radiation to Permian extinction.

Mesozoic

245-65 million years ago, Permian extinction to KT extinction.

Cenozoic

65 million years ago to present; Cretaceous extinction to present

Cambrian Radiation

544 million years ago;

Abrupt origin of most animal phyla.

Permian Crisis (Permian Extinction)

245 million years ago;

52% of Families were lost: infer that 88% of Genera, 96% of Species were lost.

Cretaceous Extinction

65 million years ago;

11% of marine families, last of the dinosaurs.

Relative Dating

Based on stratigraphy- older rocks lie below younger ones.

Life changes through time- rocks with similar fossils are of similar age.

Index Fossils

Widespread, common species that lived at a particular time.

Presence indicates rocks of particular age.

Absolute Dating

Uses change in physical constants.

Radiometric methods- isotope decay, ie. carbon-14 or uranium-238.

Continental Drift

Pangea to Laurasia and Gondwana to formation of modern continents.

Taxonomy

Description, naming, and classification of species and higher taxa.

Systematics

Classification of taxa according to genealogical relationships.

Phlogeny

the genealogical relationships of organisms.

Taxa

Are particular groups of similar organisms that are assigned a rank and name.

Branches of the family tree of species.

Taxanomic Ranks

Domain

Kingdom

Phylum

Class

Order

Family

Genus

Species

Monophyletic

Descended from a common evolutionary ancestor or ancestral group, especially one not shared with any other group.

Paraphyletic

Descended from a common evolutionary ancestor or ancestral group, but not including all the descendant groups.

Polyphyletic

Derived from more than one common evolutionary ancestor or ancestral group and therefore not suitable for placing in the same taxon.

Cladistics

A method by which phylogeny is deduced.

Based on homologies.

Plesiomorphies

Shared primitive homologies.

Apomorphies

Derived homologies.

Outgroup Comparison

Outgroup is less closely related to the taxa in question than they are to each other.

Especially useful if a primitive feature has been lost.

Molecular Phylogeny

Comparison of genetic sequences used to deduce relationships.

Some regions of the DNA evolve quickly; used to compare close relatives.

Some regions evolve slowly- used to compare distant relatives (e.g. ribosomal RNA genes)