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Wednesday, February 22 The Origin of Life “Early Earth” • Earth’s age is estimated to be 4.5 b.y.o. • Early Earth was made of super hot liquid rock • There was no ozone layer, so no protection from UV radiation • In addition to harmful UV radiation, the atmosphere was a mix of toxic gases • Not a great place to live It started getting better • After hundreds of millions of years, Earth began to cool and become solid • Water collected at the surface, creating the oceans • The first life is estimated to have appeared between 3.8 and 2.5 b.y.o. • That’s nearly 1-2 billion years after Earth was formed. How Did Life “Pop Up” in this Early Earth? • A couple scientists decided to re-create Early Earth conditions and produce organic molecules • Scientists were Stanly L. Miller and Harold C. Urey. • They began working in 1953 at the University of Chicago Miller-Urey Experiment • After replicating Early Atmosphere, the experiment was able to produce many organic molecules, including AMINO ACIDS • This supported the hypothesis that early atmosphere could produce the building blocks of life • http://www.youtube.com/watch?v=iahBQolX QH8 Where Did Life Begin? • Scientists agree that life formed as the Earth was cooling • But there are several different theories as to WHERE life started • • • • • Ocean Ridge Under Frozen Seas Deep in the Earth’s Crust Within Clay In Deep Ocean Vents In Deep Sea Vents • You Tube Video - Lets try FireFox Early Life Forms • Earliest forms of life in the fossil record date back 3.5 billion years ago • Early organisms were small, single-celled, aqueous prokaryotes • Lacked external appendages, nucleus, and limited internal structures (these were prokaryotes, remember! Prokaryotes • Two groups of prokaryotes: • Archaebacteria • Bacteria Archaebacteria • • • • Archaebacteria - Inhabit extreme conditions habitats high in toxic gases extremely salty habitats extremely hot habitats Bacteria • Bacteria – make up most of the prokaryotes alive today Eukaryotes • These more complex cells appeared about 1.5 million years ago • There are three main innovations in the development of Eukaryotic Cells • Complex structures • Sexual Reproduction • Multi-cellularity Complex Structures • Simple structures within prokaryotes are thought to have been developed into more sophisticated structures in eukaryotic cells. • Eukaryotic cells engulfed a prokaryotic cell to obtain their organelles • Phagocytosis – “to devour” • One example = Mitochondria Mitochondria have 2 layers (1 & 2) Sexual Reproduction • Most eukaryotic cells reproduce sexually • Results in recombination of genetic material! • This is a key requirement for evolution resulting in the large diversity of eukaryotes Multi-Cellularity • Single eukaryotic cells formed colonies • Individual cells begin performing specific tasks • Eventually these colonies become individual organism! (eukaryotic cell!) Remember yesterday… • King Philip Came Over For Good Soup • Kings Play Chess On Funny Green Squares • These are all below the classification of DOMAIN – Three Domains: Archaea, Bacteria, Eukarya • Below those three, 6 Kingdoms • Domain Archaea – Kingdom Archaebacteria • Domain Bacteria – Kingdom Bacteria • Domain Eukarya – – – – Kingdom Protista Kingdom Fungi Kingdom Plante Kingdom Anamalia