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Lecture

Lec 03 Origins.docx

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Department
Biology
Course
Biology 1001A
Professor
Dr.Mike
Semester
Fall

Description
Lecture 03: Origins of Life Characteristics shared by all life 1. Displays order (with the cell being fundamental unit of life) 2. Harnesses and utilizes energy (acquired from environment) 3. Reproduces 4. Responds to stimuli (changes structure, function, behaviour in response to external environment changes) 5. Exhibits homeostasis (regulates internal environment) 6. Growth and development (increases in size and/or number of cells) 7. Evolve (change over time to adapt to the environment) In what ways are the properties of life “emergent”? - Characteristics of life reflect complexity resulting from hierarchy of interactions o Begins with atoms and progresses through molecules/macromolecules to cells - Emergent: come about from simpler interactions that do not have properties found at the higher levels Characteristics of the “habitable zone” of a solar system - Water can exist in a liquid state (fundamental for development of life) Conditions of a primitive Earth - Volcanic and seismic activity (eventually cooled down into rocks of the crust) - Reducing atmosphere: almost complete absence of O 2 o Believed to contain water vapour, H , CO , NH , CH 2 2 3 4 o Lack of O2> electrons easily accepted > no O o3one layer > UV light easily reaches lower atmosphere > E needed to drive formation of molecules provided Types of molecules that were/were not synthesized by the Millar-Urey experiment - Simulated the reducing atmosphere hypothesis - Although successful, there is debate to whether atmosphere contained enough methane/ammonia to be considered reducing; some believe Earth was not reactive at all - However, still demonstrated abiotic formation of molecules critical to life o Building blocks of life synthesized: amino acids, nucleotides, simple sugars o Not polymers! Racemic mixtures produced! Importance of liposomes in evolution of first cells - Liposome: early type of protobiont (group of abiotically produced organic molecules surrounded by membrane-like structure) and are selectively permeable o Similar to vesicles o Can form spontaneously - Formation of membrane-defined compartment is critical for path toward life - Compartments allow for primitive metabolic reactions to take place in environment distinctly different from external surroundings - Concentration of key molecules would increase; allows for great complexity to be maintained in closed space Characteristics of mimivirus (mimicking microbe) that suggest it should be considered to be alive - Giant virus that can fall ill due to other viruses - Recent research shows horizontal gene transfer between mimivirus and other viruses possible, similar to bacteria - Viruses have DNA, proteins, evolve, make other viruses sick – could be alive! Characteristics of virophage - Similar to ‘bacteriophage’; virus that infects and sickens viruses - Exploits host for replication and inhibits replication of virus - Could be accommodating HGT between viruses Age of the Earth: 4.6 billion years old Age of start of life on Earth: 4 billion years ago Domains of life - Bacteria, archaea, eukarya Characteristics of LUCA; all domains of life share these, suggesting LUCA 1. Cells made of lipids 2. Genetic system based on DNA 3. DNA to RNA to protein transfer of information 4. Common system of protein assembly 5. ATP 6. Glucose and glycolysis Reason why the te
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