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BIO1130 Midterm 2.pdf

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University of Ottawa
Jon Houseman

K EYWORDS FOR H ADEAN E ON Definitions 4 Major Eons of Europe  Hadean  Achaean  Proterozoic  Phanerozoic Geological Time Scale  division of the world's history ( 4 major subdivisions of geological time) Hadean Eon  4,600 to 3,800 Ma -Formation of the solar system and planet ends with origin of life  the earliest time in Earth's history  non uniformation conditions  first forms of life  developed liquid water on earth  hell-like  partially molten surface collision with protoplanet to form Moon; planet starts to cool down Achaean Eon  3,800 to 2,500 Ma o Anaerobic bacterial life, oxygen starts to accumulate o bacteria has to make ATP from protons, protons strip off minerals  O2 started to accumulate by splitting H2O; iron oxide began to precipitate in oceans  O2 dissolves and forms oxides minerals: Sulfur Oxide  equilibrium between O2 and H2O starts to move into air  prokaryotes arise Proterozoic Eon  2,500 to 543 Ma  O2 atmosphere, single celled aerobic organisms  emergence of photosynthesis  origin and radiation of eukaryotes and simple multicellular organisms  first transfer and copy of RNA  individual cells formed a colony and the resulting cells stick together (algae) Phanerozoic Eon  543/550 Ma to Now  multicellular organisms  diversification of invertebrates, colonization of land by animals and plants  rapid increase in diversity of plants/animals  rocks and contain evident and abundant fossils  divided into 3 era; Paleozoic, Mesozoic, Cenozoic Paleozoic  543 to 251 Ma, 63 to 65 th  "ancient life"  animals began to have hard parts (shells)  characterized by the advent of fish, insects and reptiles th st Mesozoic  251 to 65 Ma, 65 to 71  characterized by the emergence and extinction of dinosaurs  origins of mammals dinosaurs radiate and thrive Cenozoic  65 Ma to Now, 72nd floor  age of mammals and birds  mass extinction of marsupials at end of Cenozoic  plant-insect codiversification Hadean Eon's 2 phases  Building phase  Stabilizing phase Building Phase  meteorites that contained lots of minerals (C, H, O) crashed into Earth's surface and provided basic building blocks of life  at this point, Earth is still a molten ball and meteorites are still flying into it on a regular basis Stabilizing Phase  Earth starts to develop a crush on top of the molten lava  Earth is unique, mass is able to hold in an atmosphere so molecules can be trapped in to survive  water vapour in air starts to cool down and H2O starts to accumulate on the Earth's surface which formed the oceans  but if another meteorite strikes then water is vapourized because of the intense amount of heat created by the impact and cycle starts over again  meteorites stopped hitting Earth at end of Hadean Eon Origins of life on Earth  special creation: benevolent surpreme being suspends laws of physics and chemistry to create life  extraterrestrial origins (Panspermia): life was formed elsewhere in universe ->first bacteria came from asteroid  chemical evolution: life evolved from assembly of larger chemical compounds ->life is based on carbon Panspermia  life came from extraterrestrial origins  no conclusive arguments (bacteria came from meteorites to Earth)  we still unsure where life came from  hypothesis proposes that life was transferred from elsewhere in the universe Wacky water  distribution of charge  cohesion, adhesion and surface tension  solvent properties  ice formation  temperature States of matter  GAS- can be compressed  LIQUID - free flow  SOLIDS -Ridged framework - breaks upon stress PLASMA-charge molecules (Irving Lagmir) Polar bonds and Hydrogen bonding  many of water's unusual properties are due to hydrogen bonding between molecules  hydrogen bonds are important to stabilizing the shapes of large molecules  hydrogen bonds result from forces created by polar covalent bonds  hydrogen bonds are the result of polar covalent bonds Surface Tension  result of an inward pull among molecules of a liquid that brings molecules on surface closer  H2O has high surface tension because of hydrogen bonds  a measure of how difficult it is to stretch or break the surface of a liquid  result in capillary forces  at the top, water molecules are in contact with air, so surface tension is created Surfactants  reduce the surface tension of water by absorbing the liquid-gas interface  can also form micelles and vesicles in water. when micelles form, polar phosphate heads stick out towards 2 O, and tails form a core that can encapsulate an oil droplet Micelles  fatty acid salts can aggregate in aqueous environments to form small, spherical monolayers  hydrophobic fatty acids tails face inside of the sphere so does not get "wet"  hydrophilic phosphate heads face towards surrounding solvent (water)  replication: o lipid cells will divide and grow on their own. Protein and nucleotides are being made in microspheres  80 to 100 molecules minimum  phospholipids can aggregate into micelles in aqueous environments o form bilayers spontaneously in vivo; 5- 6 nm thick o lipid bilayers form structural basis of all biological membranes o selectively permeable; have many properties of fluids Cohesion  ability of a molecule to stay bonded or attracted to another molecule of the same substance  high resistance of water molecules to separation  water has a high tendency to stick together due to polar characteristics  tendency of molecules to "stick together"  ex: surface tension Adhesion  The binding of a cell to another cell, or a cell to a surface  ability to remain together  intermolecular attraction between different molecules  hydrogen bonding of H2O to other polar surfaces  water sticks to other objects  adherence of molecules to the walls of conducting tubes Solvent Properties  H2O= good solvent; something that can dissolve other things  ionic compounds and low molecular weight polar covalent compounds tend to dissolve in H2O  polarity allows other ions to be attracted to H2O  forms hydration layers around large charged molecules Ice and water formation  formation of ice helps with cooling  vaporization helps organisms shed excess heat  H2O becomes less dense as it freezes because hydrogen bonds stabilize and hold water molecules farther apart Non-Polar Compound  dipoles of the element cancel each other out  symmetrical distribution of charge, so that no positive or negative poles exist Non-Polar Covalent Bonds  Have equal share of bonding electron pair  one element does not have a share of electron more than the other Polar Compound  an uneven distribution of charge, one side of molecule is either more positive or more negative  ex: H O-oxygen is more negative. net dipole is 2 zero Polar covalent Bonds  unequal sharing of electrons when bonding Hydrogen Bond  the attractive interaction of a hydrogen atom between an electronegative atom like F 2  hydrogen bonds are intermolecular between molecules not atoms  occurs in water (inorganic) and DNA (organic) Crystal Lattice of Water  very exact organization of water molecules to form a crystal like substance  when water is cooled down, it gets denser, at 4 C exactly, water forms a crystal lattice, which gets less dense because the atoms are more spread out  the lattice insults and maintains the temperature of water under it, allowing organisms to survive in the liquid portion Interstellar Space Dust  solar system was formed by gravitational
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