ORIGIN OF LIFE

• Stromatolites


  Layered rock structures produced by microbes (mainly photosynthesizing cyanobacteria) that form thin microbial films which trap mud
• Stanley L. Miller and Leslie E. Orgel: 'We do not know how life began. It is generally believed that a variety of processes led to the formation of simple organic compounds on the primitive Earth. These compounds combined together to give more and more complex structures until one was formed that could be called living. No one should be satisfied with an explanation as general as this.'
• Panspermia theory


  The idea that life developed elsewhere in the universe then arrived on earth
• Abiogenesis Theory


  The idea that life emerged from non living molecules
• Deep-Sea Vent Theory


  The idea that life may have originated around deep-sea hydrothermal vents
• Primordial Soup Theory


  The idea that life originated from a mixture of organic compound
• Primordial Soup Theory


  Also known as the Oparin-Haldane hypothesis, an idea about how life might have begun on Earth
• Primordial Soup Theory


  • The early Earth had a chemically reducing atmosphere
  • This atmosphere, exposed to energy in various forms, produced simple organic compounds ("monomers")
  • These compounds accumulated in a "soup", which may have been concentrated at various locations (shorelines, oceanic vents etc.)
  • By further transformation, more complex organic polymers, and ultimately life, developed in the soup
• Monomers


  Atoms or small molecules that bond together to form more complex structures such as polymers
• Four main types of monomers

  • Amino acid
  • Sugar
  • Fatty acids
  • Nucleotides
• Amino acids

  The monomers that build a polymer called protein
• Glucose


  The most common natural monomer that links together to form polymers of starch, cellulose and glycogen
• Fatty acids


  Also known as lipids, spontaneously arrange themselves when placed in water in order to protect their hydrophobic tails forming membranes, micelles, and vesicles
• Nucleotides


  Monomers that join together to form the structural units of RNA and DNA, as well as providing an energy source in metabolism
• Polymers


  Large molecules, also known as macromolecules, that are made up of many repeating subunits called monomers
• Polymerization


  The process by which monomers combine to form polymers
• Types of polymers


  • Synthetic Polymers (man-made)
  • Natural Polymers (occur naturally in living organisms)
  • Biodegradable Polymers (designed to break down naturally in the environment)
  • Thermoplastics (can be melted and reshaped multiple times without undergoing significant chemical change)
  • Thermosetting Polymers (undergo a chemical reaction during curing, resulting in a rigid and durable structure)
• Protocells


  Structures that are formed from the aggregation of abiotic (non-living) components, displaying certain characteristics of living cells
• Protocells


  • Self-organized, endogenously ordered, spherical collection of lipids
  • Thought to have facilitated the reproduction of RNA and therefore the exchange of genetic information at a time before the advent of DNA and proteins
  • Provided an environment for RNA to replicate and kick-started the process of life
• Self-replication


  Any behavior of a dynamical system that yields construction of an identical or similar copy of itself
• Types of self-replication


  • Biological Self-Replication (cell division in living organisms)
  • Chemical Self-Replication (certain molecules like RNA can undergo self-replication through chemical processes)
  • Artificial Self-Replication (man-made systems designed to replicate themselves)