1	Life on Earth
2	How long has life existed on Earth? Life on earth began about 3.5 to 4.0 Billion years ago. Stromatolites Fossil prokaryotes - 3.4 billion years ago
3	History of Life
4	Stromatolites
5	Stromatolites
6	Early Prokaryote Fossil
7	The Chemical Evolution Hypothesis The earth's crust began to solidify about 4.1 billion years ago. by 3.5 billion years ago there were bacteria advanced enough to form stomatolites
8	"therefore the early earth environment..." therefore the early earth environment must have allowed life to arise through spontaneous generation. CHEMICAL EVOLUTION HYPOTHESIS
9	Chemical Evolution Hypothesis Abiotic synthesis of small organic molecules (monomers ie. amino acids, simple sugars, nucleotides etc.)
10	A. I. Oparin, and J. B. S. Haldane (1920’s) postulated that the reducing atmosphere (no O₂) and high UV radiation would enhance the reactions that could have produced organic molecules.
11	"Energy sources" Energy sources No Oxygen
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13	Abiotic synthesis of simple monomers Urey - Miller experiment
14	"The Urey-Miller experiments produced all..." The Urey-Miller experiments produced all 20 amino acids, ATP, some sugars, lipids, and the purine and pyrimidine bases of RNA and DNA. These building blocks must have been joined into long chains or “polymers”.
15	Abiotic Synthesis of Polymers Proteinoids - are abiotically synthesised polypeptides Sidney Fox amino acid polymers can be made by dripping amino acids (monomers) onto hot sand, rock, or clay.
16	Formation of Protobionts Protobionts are aggregates of abiotically produced molecules able to maintain an internal environment, and exhibit some life properties.
17	"Protobionts" Protobionts Liposomes - spheres made from phospholipids mixed with water (bilayers like cell membranes)
18	First cellular functions
19	Origin of Genetic Information selfreplication requires a genetic mechanism RNA may have been the first genetic molecule “Riboszymes” short polymers of RNA have been formed with zinc as a catalyst (no enzymes) RNA is autocatalytic - RNA acts like an enzyme to make mRNA, tRNA, and rRNA.
20	Riboszymes
21	Some Alternate views... Panspermia - organic compounds may have reached earth in meteorites or comets First organisms may have originated on the deep ocean floor - “Deep Ocean Vent communities”
22	Fossil Record
23	Fossil Record
24	Dating Fossils Relative Dating Older sediments below , younger sediments on top Absolute Dating Radiometric dating
25	Radiometric dating
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28	Geological Time Scale
29	Mass Extinctions
30	End of the Cretaceous
31	"History of Life on earth" History of Life on earth
32	Prokaryotes changed the earth environment Early prokaryotes evolved all of the common metabolic pathways seen today. Photosynthesis and the “Oxygen Revolution”.
33	Origin of the Eukaryotes Oldest eukaryote fossils are about 2.1 billion years old. Endosymbioyic origin of Mitochondria and Chloroplasts Genetic annealing
34	Multicellular life The oldest multicellular fossils are found about 1.2 billion years ago. Larger organisms don’t appear until about 570 million years ago.
35	The Colonial Connection First multicellular organisms were colonies. Some cells in the colony became specialized for specific functions.
36	The Cambrian Explosion Most of the major animal phyla appeared suddenly in the fossil record during the first 20 million years of the Cambrian period. (542 – 500 million years ago).
37	Colonization of the Land The colonization of the land was one of the pivotal milestone in the history of Life. Plants , fungi and animals colonized the land during the late Paleozoic era, about 500 million years ago.
38	Continental Drift
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40	Development of genes that control development “Heterochrony” Differential growth rates and timing of development Allometric growth
41	"Heterochrony in salamander foot growth" Heterochrony in salamander foot growth Longer developmental time Shorter developmental time
42	Paedomorphosis Sexually mature stage still retains some juvenile structures.
43	Paedomorphosis
44	Changes in spatial patterns Homeotic genes control spatial organization of body parts
45	Evolutionary Novelties
46	Species Selection
47	Review: Macroevolution