Fossils Science Olympiad Latest Update Graded A+

Fossils Science Olympiad Latest Update Graded A+ Conditions required for a plant or an animal to become fossilized Hard body parts (bones, teeth, shells) - soft body parts will not fossilise, but may leave behind trace evidence (e.g. imprints) -Preservation of remains (protection against scavenging, erosion and environmental damage) -High pressure to promote mineralisation of remains (i.e. turn hard body parts into fossilised rocks) -Anoxic (low oxygen) conditions to protect against oxygen damage and prevent decomposition by saprotrophs Petrification/ petrifaction The most common method of fossilization After an organism's soft tissues decay in sediment, the hard parts — particularly the bones — are left behind. Water seeps into the remains, and minerals dissolved in the water seep into the spaces within the remains, where they form crystals. These crystallized minerals cause the remains to harden along with the encasing sedimentary rock. Permineralization Death and decay - Soft body parts are decomposed or scavenged, leaving only the hard body remains 2. Deposition - The hard remains are rapidly covered with silt and sand, and over time more layers continue to build 3. Permineralization - Pressure from the covering layers of dirt/rock cause the hard organic material to be replaced by minerals 4. Erosion / exposure - Movement of earth plates may displace the fossil and return it to the surface for discovery Mineral replacement the minerals in groundwater replace the minerals that make up the bodily remains after the water completely dissolves the original hard parts of the organism. silicification-the process in which organic matter becomes saturated with silica. A common source of silica is volcanic material. Studies have shown that in this process, most of the original organic matter is destroyed. Pyritization when they are in marine sediments saturated with iron sulfides. Pyrite is iron sulfide. As organic matter decays it releases sulfide which reacts with dissolved iron in the surrounding waters. Cast/mold If an organism completely dissolves in sedimentary rock, it can leave an impression of its exterior in the rock, called an external mold. If that mold gets filled with other minerals, it becomes a cast.An internal mold forms when sediments or minerals fill the internal cavity, such as a shell or skull, of an organism, and the remains dissolve. Imprints Imprint fossils are formed from an organism moving in some way, leaving behind a trace or track. These tracks are preserved when the clay/silt dries slowly and is covered by other sediment. Carbonization/distillation The heat and pressure from being buried in sediment can sometimes cause the tissues of organisms — including plant leaves and the soft body parts of fish, reptiles and marine invertebrates — to release hydrogen and oxygen, leaving behind a residue of s a detailed carbon impression of the dead organism in sedimentary rock. Unaltered remains meaning the fossil retains their original composition, are produced when the organism is preserved in a material that does not allow for bacterial decay, such as in amber, tar, or ice. Encasement in amber Small bugs or insects can become trapped in tree sap. Eventually the sap hardens and forms the semiprecious material called amber. Mummification a process in which the skin and flesh of a corpse can be preserved. The process can occur either naturally, or it can be intentional.