Biology IB SL

• Homeostasis


  The ability of an organism to maintain a stable internal environment despite external changes.
• DNA


  A molecule containing the genetic instructions for an organism, composed of sugar-phosphate backbone and nitrogenous bases.
• Kingdoms


  A classification of organisms into broad groupings based on shared characteristics.
• Proprioceptors


  receptors that help you to sense the relative position of your body parts like walking without watching your feet.
• Darwinian 


  natural selection to explain why species change over time, evidence from fossils and observation in Galapagos, competition for resources, natural selection to adapt to environment, isolated groups lead to new species
• Lamarckian 


  proposed that ague physical changes in an organisms lifetime are passed to offspring, organs used more grow more, organs less used shrink, this required changes passed to offspring in singular generation
• Homologous structures 


  Structures inherited from a common ancestor,Develop through Adaptive radiation, have a similar structure but may have evolved different functions ,The classic example is the Pentadactyl Limb
• adaptive radiation


  Usually rapid diversification from a common ancestor. 
• Convergent evolution


  unrelated or distantly related organism evolve similar structures/features because of similar selection pressure 
• Feedback loops


  A series of inputs and responses
• Blood pH


  Normal range is 7.35 to 7.45, slightly basic
• Effect of increased activity

  1. More muscle movement

  2. Increased need for ATP

  3. More cellular respiration

  4. More carbon dioxide in blood plasma

  5. Decreased blood pH
• Chemoreceptors


  Sense pH in blood and send nerve signals to muscles involved in breathing and ventilation
• Decreased blood pH


  Increases ventilation rate
• Negative feedback loop


  Breathing rate returns to normal when blood pH returns to homeostatic levels
• Spirometer


  • Digital or analog device connected to mouth to track breathing
  • Can see deeper and more frequent breathing during exercise
• Peristalsis


  Wave of muscle contractions that move food through digestive tract
• Voluntary digestive system movements

  • Initiation of swallowing
  • Control of defecation
• Involuntary digestive system movements

  Controlled by enteric nervous system, not central nervous system
• Digestive system is a continuous muscular tube, not reliant on gravity
• Nervous system and hormone systems integrate to control body functions
• Water


  The medium of life
• The first cells originated in water
• Water can dissolve a variety of molecules
• Water dissolves ionic and polar substances, making it an excellent solvent for transport in living organisms
• Water


  A metabolite
• Chemical reactions take place in all cells
• Chemicals involved are called metabolites
• Water = metabolite in many reactions
• Reactions where water is involved

  • Photosynthesis
  • Digestion
  • Aerobic respiration
• Many metabolic reactions in cells are catalysed by enzymes
• Enzyme activity is sensitive to temperature and reactions only occur in a narrow range of temperature
• Enzymes work best at an optimal temperature, beyond which they denature
• Electrons


  Orbit the nucleus in multiple orbits
• Electrons can change its state to a higher energy level by absorbing a photon with sufficient energy
• Types of chemical bonds

  • Nonpolar covalent bonds
  • Polar covalent bonds
  • Ionic bonds
  • Hydrogen bonds
• Covalent bond


  Holds together two atoms that share one or more pair of electrons between atoms
• Ionic bond


  An attraction between a positively charged ion and a negatively charged ion
• Hydrogen bond


  An attraction between two polar molecules
• A water molecule consists of 2 hydrogen and 1 oxygen atom, hence…H2O