The Historical Development of the Concept of Life

Chapter One The Historical Development of the Concept of Life Lesson 1 Hi! I’m Jason and I’ll be with you in this lesson. We will tackle about the Studies on the Origin of Life, Evidence on the First Forms of Life and The Three Domains of Life. Studies on The Origin of Life Many Scientists have dedicated themselves to finding out how life first appeared on Earth. All in the name of curiosity, science and discovery! 1920 Alexander Ivanovich Oparin Russian March 2, 1894 – April 21, 1980 a Soviet biochemist notable for his theories about the origin of life, and for his book The Origin of Life. He also studied the biochemistry of material processing by plants and  enzyme reactions in plant cells. John Scott Haldane Scottish May 2, 1860 –March 14/15 ,1936 a physiologist famous for intrepid self-experimentation which led to many important discoveries about the human body and the nature of gases. 1920s Oparin- Haldane Hypothesis This hypothesis suggested that if the primitive atmosphere was reducing (as opposed to oxygen-rich), and if there was an appropriate supply of energy, such as lightning or ultraviolet light, then a wide range of organic compounds might be synthesized. Oparin 1924 Haldane 1929 Hypothesized that: The Earth’s atmosphere was extremely reducing in its early stages of development. This means that the atmosphere had an excess of negative charge and could cause reducing reactions by adding electrons to compounds. These organic compounds could have undergone a series of reactions leading to more and more complex molecules. Organic molecules could have formed from simple inorganic molecules. These molecules formed colloid aggregates, or 'coacervates', in an aqueous environment. These coacervates were able to absorb and assimilate organic compounds from the environment in a way reminiscent of metabolism. They would have taken part in evolutionary processes, eventually leading to the first lifeforms. Hypothesized that: The early stages of Earth’s atmosphere was reducing, which could catalyze reactions that would form more complicated organic molecules from simpler molecules. The oceans served as a huge cooking pot where, powered by the sun or lightning, chemical reactions could occur in an aqueous environment to form a huge diversity of organic compounds. The primordial sea served as a vast chemical laboratory powered by solar energy. The atmosphere was oxygen free, and the combination of carbon dioxide, ammonia and ultraviolet radiation gave rise to a host of organic compounds. The sea became a 'hot dilute soup' containing large populations of organic monomers and polymers. Groups of monomers and polymers acquired lipid membranes, and that further developments eventually led to the first living cells. Oparin- Haldane Hypothesis Primordial Soup Soup sounds delicious! Haldane coined the term 'prebiotic soup' or 'prebiotic atmosphere' that consisted of an abundance of methane, ammonia, and water. This term became a powerful symbol of the Oparin-Haldane view of the origin of life. 1953 Harold Clayton Urey American April 29, 1893 – January 5, 1981 a physical chemist played a significant role in the development of the atom bomb, but may be most prominent for his contribution to theories on the development of organic life from non-living matter. Stanley Lloyd Miller American March 7, 1930 – May 20, 2007 a chemist who made landmark experiments in the origin of life by demonstrating that a wide range of vital organic compounds can be synthesized by fairly simple chemical processes from inorganic substances. Miller-Urey Experiment Harold Urey and his student Stanley Miller tried to calculate the chemical constituents of the atmosphere of the early Earth. They based their calculations on the view that the early atmosphere was reducing. In order to do this, they simulated early earth atmospheric conditions by creating a closed system which contained water, methane gas, ammonia, and hydrogen gas. Urey suggested that his student, Miller should attempt to synthesize organic compounds in this type of atmosphere. Miller carried out an experiment in which he passed a continuous spark discharge at 60,000 Volts through a flask containing the gases identified by Urey along with water. Furthermore, this electrical current was run through the laboratory set up to simulate the catalytic source of lightning that was present in the early atmosphere. Miller found that after a week, most of the ammonia and much of the methane had been consumed. The main gaseous products were carbon monoxide and nitrogen. In addition, there was an accumulation of dark material in the water. Few of the specific constituents of this could not be identified, but it was clear that the material included a large range of organic polymers. From the results of their experiment, they found that up to 15% of the carbon in the system was inorganic compounds that had formed in the system. This conclusion proved that organic molecules could be formed from inorganic molecules in Earth’s early atmosphere. Miller-Urey Apparatus Analysis of the aqueous solution showed that the following had also been synthesized: 25 amino acids (the main ones being glycine, alanine and aspartic acid) Several fatty acids Hydroxyl acids Amide products Evidence on the First Forms of Life FOSSILS! FOSSILS One of the strongest pieces of evidence that show many life forms existed in Earth in the past 3.5 billion years. FOSSILS One of the strongest pieces of evidence that show many life forms existed in Earth in the past 3.5 billion years. Bone Fossil Shell Fosill Plant Fossil Footprint Fossil How do fossils form? Fossil Formation Over long periods of time, particles piled up on the remains of organisms and eventually became sedimentary rocks, preserving the original body patterns of organism. Paleontologists scientists who study fossils Examine the age of fossilized organisms through radioisotope dating using radioactive materials such as the radioactive components of potassium-argon. Found remains of microscopic living cells, called microfossils, in rocks that formed 3.5 billion years ago after the Earth cooled and solidified. Microfossils a fossil or fossil fragment that can be seen only with a microscope existed in mats and formed layered structures called stromatolites. Stromatolites a calcareous mound built up of layers of lime-secreting prokaryotes, or single-celled organisms, called cyanobacteria (the blue-green algae) and trapped sediment, found in Precambrian rocks as the earliest known fossils, and still being formed in lagoons in Australasia. Cyanobacteria Believed by scientists to be the first oxygen-producing organisms that helped evolve the Earth’s early atmosphere into one that can support early life forms Cyanobacteria As these microorganisms continued generating oxygen, other photosynthetic organisms evolved and increased the level of oxygen in the atmosphere. This increased the chance of more and more oxygen reaction ammonia, a reaction that results in the release of nitrogen into atmosphere. Which resulted in the formation of the ozone layer! The ozone molecules consist of three oxygen atoms and have the chemical formula O3. A rapid evolution of life occurred after oxygen became abundant. The Three Domains of Life Life is everywhere on Earth!!! Life forms exist in different environmental conditions. There are organisms in soil, air, and even in freezing waters or deep sea thermal vents. This diversity of life constitutes many and varied lineages of organisms. Some lineages have gone extinct due to geological events brought by tsunamis, volcanic eruptions, extreme fluctuations in temperature and rising water levels. Carl Richard Woese American July 15, 1928 – December 30, 2012 a microbiologist and biophysicist. He is famous for defining the Archaea (a new domain or kingdom of life) in 1977 by phylogenetic taxonomy of 16S ribosomal RNA, a technique pioneered by Woese which revolutionized the discipline of microbiology. Domain the highest taxonomic rank of organisms in the three- domain system of taxonomy higher than the animal kingdom classification Three Domains The Three Domains Archaea Also known as ancient bacteria because they resemble the ancient prokaryotes Their morphological and genetic characteristics differ from other forms of bacteria. Lives mostly in extreme environments: Near rift vents in the deep sea at 100c Hot springs Alkaline Acid waters Guts of cows Guts of termites Guts of some marine life forms which produces methane Archaea Bacteria Also known true bacteria or simply bacteria Constitutes a great portion of prokaryotic microorganisms. Ecologically diverse, some are found in Water Soil Other organisms Some are aerobic(needs oxygen), some are anaerobic. Bacteria Eukarya Also known Eukaryotes Have membrane-bound nucleus Have eukaryotic cells composed of membrane- bound organelles Can be unicellular Protists Yeast Can be multicellular Plants Fungi Animals Eukarya