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Learning Targets 15. Recognize that evolution has occurred in all organisms and continues to occur. 17. Identify dates of big events in earth’s 4.6 billion year history. 18. Describe the basic models for the origin of life and the evidence that supports them. 19. Understand the evidence that RNA was the earliest genetic material. 27. Describe the evidence for the endosymbiotic theory. History of Earth 4.6 Billion years earth formed Hot Constantly hit with chunks of ice and rock No atmosphere 4 billion years bombardment ended earth cools oceans Atmosphere forms! Little to no oxygen Lots of H2O, Nitrogen, CO2, Methane, Ammonia & Hydrogen History of Earth Direct fossil evidence of early life on earth microorganisms 3.5 billion years ago How did THEY get there? 1. Abiotic (nonliving) synthesis of amino acids & nitrogen bases 2. Macromolecules such as protein & nucleic acids 3. Protocells (droplets of nucleic acids & proteins with a membrane to maintain internal environment) 4. Origin of self-replicating molecules History of Earth Is it possible? 1953 Stanley Miller Heated water vapor mixed with early atmosphere “lightning” cold water condensed the atmosphere (made it “rain”) collected sample water returns to “sea” Voila! Organic molecules!!...so yes, it is possible! http://viewpure.com/mF9U5x6Nxnw History of Life How do we get from amino acids to life? 2009 study abiotic synthesis of RNA in test tubes First genetic material likely was RNA Supported by important role RNA plays in making proteins (mRNA, tRNA, rRNA) RNA can also act as an enzyme (ribozyme) --> replication RNA much more versatile shape & function Big Events First single-celled organisms Earliest evidence 3.5 billion years ago Stromatolites Layered rocks form when prokaryotes bind sediment together Big Events 2.7-2.4 billion years ago oxygen-releasing Prokaryotes gradually change atmosphere! (oxidation of rocks) 1.8 billion years ago fossils of first eukaryotes Endosymbiosis Theory Aerobic cells (ex: mitochondria & chloroplasts) began living inside larger cells (either as prey or parasites) Evidences: inner membrane, own DNA (you inherit mother’s mitochondrial DNA), replication similar to prokaryotes http://viewpure.com/3ESXvLHceDc Big Events 1.2 Billion years ago Multicellular eukaryotes red algae 535-525 million years ago Cambrian EXPLOSION!!!! Present day phyla began to appear Predators (claws & other prey-capturing features appear) Prey (defensive mechanisms appear sharp spines, heavy body armor) Big Events 500 Million years ago Plant and animal begin to colonize land Plants colonized land with company of fungi…even now, a lot of plants rely on fungi to help absorb nutrients Animals arthopods among the first (450 mya), tetrapods (365mya) 195,000 years ago humans arrived (lineage diverged from other primates 6-7 mya) Learning Check Evolution is Oldest fossils are A) only a theory and still needs to be proven A) 3.5 billion years old and are prokaryotes B) an explanation for how life came to be, but no longer happening B) 1.4 billion years old and are prokaryotes C) observed currently, but cannot explain the evidence we see in the history of life C) 3.5 billion years old and are eukaryotes D) observed currently and best explains the evidence we see in the history of life. D) 1.4 billion years old and are eukaryotes