Lecture 02 Outline Chapter 25

Lecture 02 Outline Chapter 25 - LECTURE 2 Chapter 25....

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LECTURE 2 Chapter 25. History of Life II The fossil record documents the appearance and disappearance of organisms in geological history (Fig. 25.7). Archaean Proterozoic Phanerozoic Note: prokaryotes, atmospheric oxygen, single-celled eukaryotes, multicellular eukaryotes, animals, plants Geological Table (Fig. 25.1) 3 eons lasting 4.6 billion years Eons Eras Period Epochs. Oldest material on earth nearly 4.4 BYA zircon: mineral from Australia. Dated by oxygen isotope ratios. Oldest rocks on earth 3.8 BYA. Issua Greenland ~3.5 BYA 1 st cells appeared in fossil record (first record of life)…but must have evolved earlier than this! 3.5 to 2 BYA Prokaryotes were only organisms on earth Remember Prokaryote = single-celled organism with no membranous nucleus or organelles. Evidence of first prokaryotes fossilized stromatolites : layered rock that forms when some prokaryotes bind thin films of sediment. Fossil Cyanobacteria (Domain bacteria). Common in fossil record from ca. 3.5 BYA in fossilized stromatolites. Morphology of modern forms very similar Fig. 26.21. Life falls into 3 domains : Eukarya Archaea Bacteria Energy sources for the 1 st prokaryotes First Prokaryotes were Autotrophs: Autotrophs organisms that synthesize molecules they need for growth and 1
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metabolism. To do so: ENERGY must be harvested. Either from SUNLIGHT or by breaking chemical bonds in energy-rich compounds such as molecular hydrogen sulfide or methane. Early Prokaryotes
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Lecture 02 Outline Chapter 25 - LECTURE 2 Chapter 25....

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