Geology Interlude E

Fossil

The remnant, or trace, of an ancient living organism that has been preserved in rock or sediment. (page 331)

Paleontology

The study of ancient life and its evolution as recorded by fossils. (page 331)

Paleontologist

A scientist who specializes in studying and interpreting fossils. (page 331)

Evolution

See Theory of Evolution by Natural Selection. (page 332)

Fossilization

The process of forming a fossil. (page 332)

Mold

A cavity in sedimentary rock left behind when a shell that once filled the space weathers out. (page 333)

Cast

Sediment that preserves the shape of a shell it once filled before the shell dissolved or mechanically weathered away. (page 333)

Permineralization

The fossilization process in which plant material becomes transformed into rock by the precipitation of silica from groundwater. (page 333)

Petrified wood

Wood that has undergone permineralization and has turned into agate; growth rings and cell walls may remain visible in samples. (page 333)

Biomarker

A molecule or set of molecules that could only have been produced by living organisms; their presence can be used for correlation and for determining the time at which life on the Earth began. (page 334)

Macrofossil

A fossil large enough to be seen with the naked eye. (page 334)

Microfossil

A fossil that can be seen only with a microscope or an electron microscope. (page 334)

Preservation potential

The likelihood that an organism will be preserved as a fossil. (page 335)

Extraordinary fossil

A rare fossilized relict, or trace, of the soft part of an organism. (page 335)

Taxonomy

The study and classification of the relationships among different forms of life. (page 336)

Domain

In the context of discussing the classification of organisms, it is the highest rank in a taxonomic hierarchy; there are three domains (Bacteria; Archaea; Eukarya). (page 336)

Kingdom

In the context of taxonomy, it is the second highest rank of life (beneath domain); examples of kingdoms include Animalia, Plantae, and Fungi. (page 336)

Morphology

The form or shape of an object (or the study of form or shape); for example, fossil shells can be classified based on the morphology of their shells. (page 336)

Cambrian explosion

The remarkable diversification of life, indicated by the fossil record, that occurred at the beginning of the Cambrian Period. (page 338)

Phylogeny

The study of how a species of organism evolves. (page 338)

Phylogenetic tree

A chart representing the ideas of paleontologists showing which groups of organisms radiated from which ancestors. (page 338)

Natural selection

The process by which the fittest organisms survive to pass on their characteristics to the next generation. (page 339)

Theory of evolution by natural selection

The idea that species change over time, new species appear, and old species disappear, due to the survival of the fittest. (page 339)

Extinction

The death of the last members of a species so that there are no parents to pass on their genetic traits to offspring. (page 340)

Biodiversity

The number of different species that exist at a given time. (page 340)

Mass-extinction event

A time when vast numbers of species abruptly vanish. (page 340)