2 by dripping solutions of amino acids onto hot dry

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2. By dripping solutions of amino acids onto hot, dry sand, clay, or rock, researchers have shown  that the amino acids will hook together without the help of enzymes. C. Protobionts:  1. These are collections (clumps or aggregates) of abiotically produced molecules surrounded by  membrane-like structure 2. Internal chemical environment different than outside environment 3. In the lab, membrane-bound droplets called liposomes will reproduce be selectively permeable,  respond osmotically,  and exhibit simple metabolism (Fig. 25.3) D. Self-Replicating RNA and the Dawn of Natural Selection 1. First genetic material is believed to have been RNA not DNA.  
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2. Ribozymes are RNA catalysts that can copy short pieces of RNA in a test tube, which has  nucleotide building blocks. Ex) can make complementary copies of short pieces and this has  been replicated in a test tube) more effective at using resources and increase in number  through natural selection 25.2 The fossil record documents the history of life A.  Fossils (any preserved organism or impression left by an organism) are used to reconstruct phylogenies  (evolutionary histories). (Fig. 25.4) 1. Sedimentary rocks: richest source of fossils.   Rocks are formed by layers of sediment (sand, silt, etc)  laid down over time 2. Fossils are usually from mineral-rich hard parts of organisms (bone, teeth, shells) 3. Petrification:  minerals dissolved in ground water seep into soft tissues and preserve them (petrified  trees) 4. Amber (solidified tree sap) preserves insects well.  No bacteria can get to them. 5. Freezing prevents decomposition.  (Wooly mammoth) Stromatolites are fossilized bacteria B.  Fossil record is incomplete.
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