Biology 1201A Lecture Notes - Lecture 18: Phylogenetic Tree, Invertebrate, Stromatolite
10 Dec 2015
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Document Summary
Usually the sedimentary rock strata are distinctive because of their colour, mineral composition, particle size, and thickness. As such, if they have not been disturbed (uplifted, warped, or inverted by geologic processes) the strata are arranged in the order that they"re formed, so the top ones are the youngest. The spectacular mounted fossil skeletons we see in museums were formed when dissolved minerals enter the spaces within the bones and then solidified. Some fossils, mainly plant fossils are moulds or impressions, with fossils that are preserved in amber showing fine details of the organisms. This is because these organisms were likely compressed shortly after death. Footprints can be fossilized when an animal walks across mud, and even droppings and gastroliths (stones in the stomach used to grind food), have been preserved as fossils. Some fossilized remains such as early humans are frozen and mummified. Petrified forests are trees fossilized by minerals. The fossil record is incomplete because few organisms fossilize.
