Ch 10 How We Are Related Flashcards
Fossil record
The information derived from fossils. The fossil record is arranged in chronological order and helps us map the history of life on Earth, placing species in the appropriate geologic time frame.
Cambrian explosion
A period (~ 535 mya) of rapid diversification of multicellular life, characterised by the evolution of hardened body parts such as shells or bones.
Extinction
The dying out of a species on a global or regional level.
Fossil
The preserved body, impressions, or traces of a dead organism.
Fossilisation
The process by which an organism becomes a fossil.
Sediment
Naturally occurring solid material, such as earth and rock, that is broken down into very fine pieces and typically settles at the bottom of liquid.
Sedimentary rock
Rock that has formed through the accumulation of sediment that hardens under pressure.
Permineralised fossil
Fossil formed when mineral-rich groundwater deposits minerals like silica and calcite into organic material, creating a mineral relic.
Mould fossil
Fossil formed when a living thing decomposes underneath sediment, creating a cavity in the shape of the dead organism.
Cast fossil
Fossil formed when a mould fossil is filled with sediment.
Trace fossil
Fossil or structure indicating the presence of organisms, rather than the organisms themselves (e.g. nests, footprints, and burrows)
Relative dating
A dating technique used to determine the relative age of a fossil by comparing its position to other fossils or rock in surrounding rock strata (layers).
Absolute dating
A dating technique used to determine the absolute age of a fossil by measuring the relative amounts of radioisotopes to their products. Also known as radiometric dating.
Fossil succession
The principle that fossils of the same age will be in the same layer of sedimentary rock, and fossils found in higher or lower sedimentary layer will be younger or older, respectively. Also known as faunal succession.
Relative age
The age of a fossil as determined by relative dating techniques. Describes the age of a fossil compared to other fossils, instead of a fossil’s exact age in years.
Stratum (pl. strata)
A layer of sedimentary rock.
Index fossil
A group of widespread fossils which existed for a short period and have a known age. Can be used as a reference to easily determine the age of unknown fossils.
Transitional fossil
A fossil that shows traits that are common to both its ancestral group and its descendant group. They are particularly important when the descendant species is physically very distinct from the ancestral species, such that the transitional fossil can help demonstrate evolutionary changes between the two.
Absolute age
An estimate of the age (in years) of a fossil or rock.