Biology 1001A Lecture Notes - Lecture 17: Last Universal Common Ancestor, Family Tree, Phylogenetic Tree
16 Aug 2017
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How the relative position of fossils in sedimentary rock strata (higher vs lower) reveals their relative age. Sediments found in any one place form distinctive strata (layers) that usually differ in colour, mineral composition, particle size, and thickness. If they have not been disturbed, the strata are arranged in the order in which they formed, with the youngest layers on top. But strata have sometimes been uplifted, warped, or even inverted by geologic processes. Ways in which fossils can form: skeleton fossils form when dissolved minerals entered the spaces within the bones and then solidified, fossils preserved in amber show fine details of the organisms, plant fossils are moulds or impressions. Reasons why the fossil record is incomplete: few organisms fossilize completely, some organisms are more likely to fossilize than others, natural processes destroy many fossils. Importance of animal skeletons to the fossil record.
