Final answer:
Most organisms decompose after death, and only occasionally do parts like bones or teeth become fossils. Unaltered fossil preservation is rare, requiring extraordinary conditions such as rapid burial or entrapment in amber. Fossils provide crucial information about past life and the earth's history.
Step-by-step explanation:
Organisms do not always remain intact during and after the process of fossilization. In most cases, the soft tissue of organisms decomposes quickly after death. Occasionally, the hard parts like bones, teeth, or shells may mineralize and become fossils. For an organism to be preserved as a fossil, it must be covered quickly by sediments or preserved in some other exceptional circumstance such as being trapped in tree resin (amber), frozen in glaciers, or trapped in tar. Despite these possibilities, the fossil record is very incomplete because the conditions for fossilization are rare, leading to very few organisms being preserved in this way. Unaltered fossils are exceptionally rare, the most notable examples being organisms trapped in amber or preserved as mummified remains like a wooly mammoth found in Alaska. Fossils typically involve some degree of alteration, such as permineralization, where porous materials like bones are infiltrated with mineral-rich groundwater, turning them into stone. Soft tissue is especially difficult to preserve as it needs to be buried in an oxygen-free, low-energy environment quickly to avoid decay. Figures and fossil collections can show different preservation states, such as external molds showing fine details like fish scales or leaves' veins, and can help us understand the paleoenvironment and paleoecology of past organisms. They are not just curiosities but key evidence of past life and evolution.