16 Flashcards
(20 cards)
fossil
any preserved trace left of an animal that lived long ago
Artefacts
are objects that have been deliberately made by humans. (Stone tools, beads, carvings)
dating
determining the age of excavated artefacts or fossils
Absolute dates
the actual age of the specimen in years
Relative dates
tell you wether one sample is older or younger than another
Potassium-argon dating technique
based on the decay of radioactive potassium to form calcium and argon
isotopes
different forms of the same element (different number of neutrons in nucleus)
Carbon-14 or radiocarbon dating
based on the decay of the radioactive isotope of carbon, carbon-14 to nitrogen.
Half-life
e
Accelerator mass spectrometry (AMS) radiocarbon dating
involves breaking the sample up into its constituent atoms so that the number of atoms in each isotope of carbon can be counted. (can use v small samples)
organic compound
must contain C
Dendrochronology
(tree ring dating) another type of absolute dating that counts number of tree rings.
Stratigraphy
is the study of layers or strata/
The principle of superposition
assumes that in layers of sedimentary rock, the top are younger than those beneath them
The correlation of rock strata
involves matching layers of rock from different areas
Index fossils
certain fossils of great value because they are widely distributed and were present on Earth for only a limited period pf time
Fluorine dating
based on the fact that when a bone is left in soil, fluoride ions which are present in the water in the soil, replace some of the ions in the bone itself
Phylogenetic trees(dendrogram)
represents the evolutionary relationships between a number of organisms derived from a common ancestor
geological time scale
Earths geological history hs been divided up into eras, subdivided into periods, periods divided into epochs
Conditions for fossil formation:
1) a quick burial of material
2) presence of hard body parts
3) an absence of decay organisms
4) a ling period of stability
