Origins of Life Early Idea: Spontaneous Generation The idea that non-living material can produce life—Life magically appears! Examples Meat produces maggots Mud produces fish (mudskippers) Grain produces mice

Origins of Life Francesco Redi disproved the theory of spontaneous generation in 1668 Experiments with rotting meat

Origins of Life Also during this time, scientists were just beginning to use microscopes… They were able to see that microorganisms were EVERYWHERE! Even though Redi was able to disprove the theory of spontaneous generation, many scientists thought that microorganisms arose spontaneously from a “vital force” in the air

Origins of Life Louis Pasteur Disproved the spontaneous generation of microorganisms Experiments with broth

Origins of Life Pasteur’s experiments showed that microorganisms do not arise from the broth alone even in the presence of air Biogenesis became the accepted theory about the origin of life Biogenesis is the idea that living organisms only come from other living organisms

How Did Life Begin On Earth? Currently, there is no way to know for certain how life began on Earth. Scientists have developed theories about the origins of life, using the scientific method to test hypotheses about conditions on early Earth. Only about 1% of all known species exist today 99% are extinct!

How Did Life Begin On Earth? Early Earth Very Hot Meteorite Collisions Volcanoes Very little oxygen Atmosphere made of H2O Vapor, CO2, Nitrogen gas, Methane & Ammonia

How Did Life Begin On Earth? Ingredients for Life: Before life can occur, you need the molecules of life 1st: Formation of simple organic molecules 2nd: Organization into complex organic molecules Proteins/Carbohydrates/Nucleic Acids/Lipids So… How did this happen in such a harsh environment?

How Did Life Begin On Earth? Alexander Oparin (1930’s) Life began in the oceans Sun, lightening & heat caused chemical reactions producing organic molecules These molecules washed into the ocean forming primordial soup

How Did Life Begin On Earth? Miller & Urey (1953) Tested Oparin’s theory by simulating conditions on early Earth in a lab Mixture of H2O vapor, ammonia, methane, and hydrogen gasses were zapped with electrodes Cooled gasses condensed in flask After a week, several kinds of amino acids, sugars, and other small organic molecules were present in the flask

How Did Life Begin On Earth? The next steps in the origin of life were the formation of complex organic molecules and cells. Sidney Fox – produced protocells by heating solutions of amino acids Protocells – a large ordered structure, enclosed by a membrane, that carries out some life activities, such as growth and division.

The First True Cells First forms of life were prokaryotes that likely evolved from protocells Anaerobic Heterotrophs Later, early prokaryotes evolved to be able to make their own food These were similar to archaebacteria and used chemosynthesis to produce their food

The First Photosynthetic Prokaryotes Likely the next kind of organisms to have evolved were: Able to use sun to make glucose Produced OXYGEN, which changed Earth’s atmosphere Lightening + Oxygen = Ozone Layer formation

The First Eukaryotes The Endosymbionic Theory Lynn Margulis – 1960’s Eukaryotes evolved from prokaryotes Evolved b/c of symbiotic relationships between early prokaryotic bacteria (mitochondria & chloroplasts)

The Record Of Life Paleontologists – scientists who study ancient life, often using fossil evidence Uses fossils to determine look and characteristics of the organism, as well as the climate and geography of the area. Fossils – evidence of an organism that lived long ago typically found in sedimentary rock compressed clay/sand/mud

The Record Of Life Different kinds of fossils: Trace Casts Imprints Petrified Molds Amber Frozen Trace Fossil Cast Fossil Imprint Fossil Mold Fossil Amber Fossil Frozen Fossil

The Record Of Life Fossil Aging Relative Dating – The deeper the fossil, the older it is. Radiometric Dating – Uses radioactive isotopes to determine specific ages of fossils. Potassium-40: used for really old fossils Carbon-14: used for fossils less than 50,000 years old

Geologic Time Scale Chronology, or calendar, of the Earth’s history. Based on evidence from rocks Organized according to living organisms of the time period 4 different eras

Time Line of Earth’s History 4.6 billion ybp – Earth forms hot/volcanoes/meteors/ancient atmosphere 3.9 billion ybp – Earth cools water vapor condenses. Millions of yrs of rainstorms create oceans 3.9-3.5 billion ybp – Precambrian Era First organisms appear, photosynthesizing organisms add OXYGEN to atmosphere 3.5 billion ybp – unicellular prokaryotes 1.8 billion ybp – eukaryotic organisms develop 544 million ybp – multicellular eukaryotes (sponges & jellyfish)

Time Line of Earth’s History 540 million ybp – Paleozoic Era Animals & plants appeared 500 million ybp – first vertebrates 430 million ybp – first land plants 390 million ybp – first amphibians 300 million ybp – first reptiles 250 million ybp – mass extinction

Time Line of Earth’s History 245 million ybp – Mesozoic Era Age of the Dinosaurs 245 million ybp – Triassic Period 225 million ybp: first dinosaurs 210 million ybp: first mammals 208 million ybp – Jurassic Period 150 million ybp: first birds 144 million ybp – Cretaceous Period 135 million ybp: continents broke apart & began to drift 66 million ybp: mass extinction of dinosaurs

Time Line of Earth’s History 66 million ybp – Cenozoic Era Era in which we now live 30 million ybp – Primates appear 200,000 ybp – Modern Humans Appear