cumulative bio 1107

• Unifying themes of life


  • Organization
  • Information
  • Energy and Matter
  • Interactions
  • Evolution
• Organization


  The hierarchy of life unfolds as follows: biosphere > ecosystem > community > population > organism > organ system > organ > tissue > cell > organelle > molecule > atom. With each step up, new properties emerge (emergent properties) as a result of interactions among components at the lower levels.
• Structure and function


  Are correlated at all levels of biological organization
• Cell


  The lowest level that can perform all activities required for life
• Types of cells


  • Prokaryotic
  • Eukaryotic
• Eukaryotic cells


  Have a DNA-containing nucleus and other membrane-bound organelles
• Prokaryotic cells


  Lack membrane-enclosed organelles
• Genetic information


  Encoded in the nucleotide sequences of DNA
• Gene expression


  DNA sequences (called genes) program a cell's protein production by being transcribed into mRNA and then translated into specific proteins
• Gene expression also produces RNAs that are not translated into proteins but serve other important functions
• Energy flow


  Flows through an ecosystem. Producers convert energy from sunlight to chemical energy, which is used by organisms to do work and is eventually lost from the ecosystem as heat.
• Chemicals


  Cycle between organisms and the environment
• Organisms


  Interact continuously with physical factors. Plants take up nutrients from the soil and chemicals from the air and use energy from the sun. Interactions among plants, animals, and other organisms affect the participants in varying ways.
• Evolution


  The process of change that has transformed life on Earth, accounts for the unity and diversity of life. It also explains evolutionary adaptation—the match of organisms to their environments.
• Domains of life


  • Bacteria
  • Archaea
  • Eukarya
• Scientific inquiry


  Scientists make observations (collect data) and use inductive reasoning to draw a general conclusion, which can be developed into a testable hypothesis. Deductive reasoning makes predictions that can be used to test hypotheses.
• Controlled experiments


  Designed to demonstrate the effect of one variable by testing control groups and experimental groups differing in only that one variable.
• Scientific theory


  Broad in scope, generates new hypotheses, and is supported by a large body of evidence.
• Observations and experiments must be repeatable, and hypotheses must be testable.
• Technology


  A method or device that applies scientific knowledge for some specific purpose that affects society as well as for scientific research.
• Diversity among scientists promotes progress in science.
• Major elements in living matter


  • Oxygen
  • Carbon
  • Hydrogen
  • Nitrogen
• Atom


  The smallest unit of an element, has the following components: protons, neutrons, electrons
• Electrically neutral atom


  Has equal numbers of electrons and protons; the number of protons determines the atomic number.
• Electron shells


  Electrons occupy specific electron shells; the electrons in a shell have a characteristic energy level. Electron distribution in shells determines the chemical behavior of an atom.
• Valence shell


  An atom that has an incomplete outer shell is reactive.
• Chemical bonds


  Form when atoms interact and complete their valence shells. Covalent bonds form when pairs of electrons are shared. Also single bond and double bond.
• Molecules


  Consist of two or more covalently bonded atoms.
• Electronegativity


  The attraction of an atom for the electrons of a covalent bond.
• Polar covalent bond


  Electrons are pulled closer to the more electronegative atom, such as the oxygen in H2O.
• Ion


  Forms when an atom or molecule gains or loses an electron and becomes charged.
• Ionic bond


  The attraction between two oppositely charged ions, such as Na+ and Cl-.
• Chemical reactions


  Change reactants into products while conserving matter. All chemical reactions are theoretically reversible. Chemical equilibrium is reached when the forward and reverse reaction rates are equal.
• Weak interactions


  Reinforce the shapes of large molecules and help molecules adhere to each other. A hydrogen bond is an attraction between a hydrogen atom carrying a partial positive charge and an electronegative atom carrying a partial negative charge.
• Molecular shape is usually the basis for the recognition of one biological molecule by another.
• Hydrogen bonding


  Keeps water molecules close to each other, giving water cohesion. Hydrogen bonding is also responsible for water's surface tension.
• Water's high specific heat


  Heat is absorbed when hydrogen bonds break and is released when hydrogen bonds form. This helps keep temperatures relatively steady, within limits that permit life.
• Evaporative cooling


  Based on water's high heat of vaporization. The evaporative loss of the most energetic water molecules cools a surface.
• Ice floating


  Because it is less dense than liquid water. This property allows life to exist under the frozen surfaces of lakes and seas.
• Water as a solvent


  Its polar molecules are attracted to ions and polar substances that can form hydrogen bonds. Hydrophilic substances have an affinity for water; hydrophobic substances do not.