10A - The Fossil Record

Question 1

fossil record

Answer 1

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.

Question 2

Cambrian explosion

Answer 2

A period (~535 mya) of rapid diversification of multicellular life, characterised by the evolution of hardened body parts such as shells or bones.

Question 3

fossil

Answer 3

The preserved body, or traces of a dead organism.

Question 4

fossilisation

Answer 4

The process by which an organism becomes a fossil.

Question 5

sediment

Answer 5

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.

Question 6

sedimentary rock

Answer 6

Rock that has formed through the accumulation of sediment that hardens under pressure.

Question 7

permineralised fossil

Answer 7

Fossil formed when mineral-rich groundwater deposits minerals like silica and calcite into organic material, creating a mineral relic.

Question 8

mould fossil

Answer 8

Fossil formed when a living thing decomposes underneath sediment, creating a cavity in the shape of the dead organism.

Question 9

cast fossil

Answer 9

Fossil formed when a mould fossil is filled with sediment.

Question 10

trace fossil

Answer 10

Fossil or structure indicating the presence of organisms, rather than the organisms themselves (eg. nests, footprints and burrows).

Question 11

relative dating

Answer 11

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).

Question 12

absolute dating

Answer 12

A dating technique used to determine the absolute age of a fossil by measuring the relative amounts of radioisotopes to their products. AKA radiometric dating.

Question 13

fossil succession

Answer 13

The principle that fossils of the same age will be in the same layer of sedimentary rock, and fossils found in a higher or lower sedimentary layer will be younger or older, respectively. AKA faunal succession.

Question 14

relative age

Answer 14

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.

Question 15

stratum (pl. strata)

Answer 15

A layer of sedimentary rock.

Question 16

index fossil

Answer 16

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.

Question 17

transitional fossil

Answer 17

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.

Question 18

absolute age

Answer 18

An estimate of the age (in years) of a fossil or rock.

Question 19

radioactive isotope

Answer 19

A radioactive atom of a specific element. This atom breaks down in to a predictable and stable product. AKA radioisotope.

Question 20

half-life

Answer 20

The time taken for half the mass of a radioisotope sample to break down into its products.

Question 21

dating period

Answer 21

The range of time since fossilisation in which a particular radioisotope series can be used. Beyond his period, most of the radioisotope will have broken down into its products, meaning that it is too difficult to estimate the fossil’s age.

Question 22

radiocarbon dating

Answer 22

A form of absolute dating used to determine the age of a fossil by measuring the properties of radiocarbon, a radioactive isotope of carbon. AKA carbon dating and radioactive carbon dating.