The last eonphanerozoic is broken up into 3 eras

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The last eon—Phanerozoic is broken up into 3 era’s also—the Paleozoic, Mesozoic, and the Cenozoic 1. prokaryotes 2. oxygen in the atmosphere 3. single selled eukaryotes 4. multi celled eukaroytes 5. appearance of animals The first single-celled organisms the first organisms on earth were prokaryotes- DNA, membrane, no nucleus the oldest known fossils are stromatolites- formed by the accumulation of sedimentary layers on bacterial mats (3.5 billion years ago) prokaryote were the sole ihabitants of earth from 3.5to about 2.1 billion years ago photosynthesis and the oxygen revolution most of the atmospheric oxygen is of biological origin by about 2.7 billion years ago, oxygen began to accumulate in the atmosphere and rusted iron-rich terrestrial rocks “oxygen revolution” 2.7~2.3 billion years ago, led to extinction of many prokaryotes the first eukaryotes
oldest fossils of eukaryotes cells date back to 2.1 billion years ago membrane, cytoplasm, membrane enclosed organelles, DNA throughout nucleus, nucleus (membrane closed) Endosymbiotic theory- proposes that mitochondria and plastids (chloroplasts & related organelles) were formerly small prokaryotes living within larger host cells a n endosymbiont is a cell that lies within a host cell serial endosymbiotic hypothesis suggests that mitochondria evolved before plastids through a sequence of endosymbiotic events THE ONLY ORGANELLES NOT IN THE EDOMEMBRANE SYSTEM ARE THE CHOLORPLAST AND THE MITOCHONDRIA BECAUSE OF THIS THOERY Key evidence supports an endosymbiotic origin to mitochondria and plastids endosymbiont inner membranes similar to plasma membranes of prokaryotes division is similar in these organelles and some prokaryotes these organelles transcribe and translate their own DNA their ribosomes are more similar to prokaryotes than eukaryotic ribosomes the evolution of eukaryotic cells allowed for a greater diversity for unicellular forms The origin of multicellularity bangiomorph a is a species of red algae that lived 1.2 bya and provides the oldest known fossil of multicellular eukaryotes large more diverse multicellular eukaryotes only appear in fossil record about 600 million years ago ediacaran biota were soft bodied organisms that lived from about 600 to 355 million years ago The Cambrian explosion Cambrian explosion refers to the sudden appearance of fossils resembling modern animal phyla in the Cambrian period 535 to 525 million years ago DNA analysis suggests that many animal phyla diverged before the Cambrian explosion, perhaps as earlt as 700 million years ago to 1 billion years ago Fossils from china suggest that the cambiran explosion had a “long fuse” The colonization of land Fungi, plants and animals began to colonize land about 500 million years ago Vascular tissue ( tissue that helps plants transport water in their bodies) in plants appear about 420 million ears ago Other adaption, like a waxy cuticle (helps prevent water loss) , facilitated living on land by preventing water loss

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