human bio evidence for evolution - LESSON 5 FOSSIL EVIDENCE

fossils def

preserved remains, impressions or traces of past life

3 examples of fossils

bones, footprints, teeth

2 ways fossils can be discovered

by erosion or excavation

artefacts

objects made by a human being, typically one of cultural or historical interest. provide info about how that person lived

petrified fossils

where bones, shells and other hard parts are replaced by other minerals from surrounding rocks.

mould

a cavity inside a rock that forms when a trapped organism in sediment decomposes. (its the exact shape and size of the organism)

cast

when minerals from surrounding rock seep into a mould and harden. this is an identical copy of the organism

carbonised fossils

• when extreme heat and pressure cause chemical change to fossils

• all of the organisms material, except carbon, are converted to gases

• usually black in colour

trace fossils

record the activities or organisms: eg tracks, burrows, tooth marks

unaltered fossils

• when whole fossilised organisms are found

• very rare as predators, scavengers or decomposers usually attack them before they are preserved

• some are mummified in deep dry caves or preserved in glaciers, amber or tar pits