Dating of Fossils

Dating of Fossils - The First Eukaryotes-Oldest fossils of...

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Dating of Fossils - Order of fossils in rock strata tells us the sequence in which they were laid down - This provides relative ages, not absolute dates Radiometric Dating - Can determine absolute ages of fossils -Radioactive isotopes decay into a daughter isotope at a fixed rate -1/2 life: amount of time it takes for 50% of an isotope to decay Concept 25.3: Key events in life’s history include the origins of single-celled and multi-celled organisms and the colonization of land What were the earliest organisms like? First organisms were prokaryotes - Bacteria & Archaea - Fed on accumulated organic molecules (heterotrophic) some were likely autotrophic Oxygenic Photosynthetic bacteria evolved b/n 3.5 & 2.7 BYA - CO2+H2O->Food+O2 Oxygen begins accumulating in the atmosphere 2.7 BYA
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Unformatted text preview: The First Eukaryotes-Oldest fossils of eukaryotic cells are 2.1 BY old-Endosymbiotic Theory-Mitochondria & plastids were formerly small prokaryotes living within larger host cells- Were possibly undigested prey or internal parasites or mutualists Clock Analogy-Shows time scales involved in the history of life on Earth Phylogeny and the Tree of Life Chapter 26 Phylogeny: the evolutionary history of a species or group of related species Systematics: an analytical approach to understanding the diversity and relationships of organisms Concept 26.1: Phylogenies show evolutionary relationships-Taxonomy: the ordered division of organisms into categories based on a set of characteristics used to assess similarities and differences...
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