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! 

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  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 

Big Events  1.2 Billion years ago  Multicellular eukaryotes  red algae  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 A) only a theory and still needs to be proven B) an explanation for how life came to be, but no longer happening C) observed currently, but cannot explain the evidence we see in the history of life D) observed currently and best explains the evidence we see in the history of life.  Oldest fossils are A) 3.5 billion years old and are prokaryotes B) 1.4 billion years old and are prokaryotes C) 3.5 billion years old and are eukaryotes D) 1.4 billion years old and are eukaryotes