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Science Study Sheet
Fossils
Test Date_______________
Know these facts:
1. Soft parts of a sharks body would not be preserved as a fossil because they
would rot before fossilization could occur.
2. Prehistoric animals were preserved as whole animals in amber.
3. Fossil bone is much heavier than original bone because it is now made of minerals.
4. Trilobites found in limestone in Millard County are evidence that parts of Utah were
once the sea floor of an ancient ocean.
5. Fossils are often found in limestone.
Know the difference between these types of fossils:
Preserved Fossils-This is formed when an insect gets trapped in tree sap. Over time this
becomes fossilized amber. You can also have preserved fossils in ice and tar.
Mineral Replacement Fossils-Seeping water dissolves bone and minerals in the water
replace the bone. This changes to stone. This can happen to wood also.
Impression Fossils*Imprint: thin organisms such as feathers, leaves, or fish fall into sediment before it
hardens. When the organism decomposes only the carbon remains on the rock.
*Mold and Cast: Mold fossils are imprints made by larger organisms. When the
organism dies, it is covered by sediments, It decomposes slowly, leaving a cavity that
keeps the exact shape and size. Later the cavity may fill with sediments that take the
shape of the mold. This is the cast, which looks like the organism on the outside.
*Trace: These fossils are marks or tracks left by ancient organisms which are preserved
in sedimentary rocks. The are fossils of organisms that were at that spot, then move on.
Example – footprints in soft mud, burrows, coprolites (dino dung).
Think about:
--Why is it important to study fossils?
--What types of informational text would be best for researching fossils?
--If a piece of sandstone had ripples across it, What might have been preserved?